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All questions of DNA Replication (BIO) for MCAT Exam
How many base pairs are there in every helical turn of Watson-Crick double helix model?- a)32.3
- b)11.6
- c)20
- d)10.4
Correct answer is option 'D'. Can you explain this answer?
How many base pairs are there in every helical turn of Watson-Crick double helix model?
a)
32.3
b)
11.6
c)
20
d)
10.4
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Michael Warren answered |
Understanding the Watson-Crick Double Helix
The Watson-Crick model of DNA describes its structure as a double helix, where two strands twist around each other. An important aspect of this structure is the number of base pairs that occur in one complete turn of the helix.
Base Pairs Per Turn
- The correct answer to how many base pairs are present in every helical turn is 10.4.
- This value represents the average number of base pairs that participate in a single complete turn of the helical structure of DNA.
Significance of 10.4 Base Pairs
- The number 10.4 is derived from the helical structure of B-DNA, which is the most common form of DNA found in living organisms.
- Each helical turn spans approximately 34 angstroms (3.4 nanometers) in length, making the compact structure of DNA efficient for storage and replication.
Implications of Base Pair Count
- Understanding the number of base pairs per turn is crucial for various biological processes, including DNA replication and transcription.
- The uniformity of base pairs per turn aids in the stability and predictability of DNA interactions with proteins and enzymes.
Conclusion
- The average of 10.4 base pairs in each helical turn showcases the intricate design of DNA, allowing it to fulfill its roles in genetics and cellular function efficiently. This knowledge is foundational in molecular biology, genetics, and biochemistry studies.
The Watson-Crick model of DNA describes its structure as a double helix, where two strands twist around each other. An important aspect of this structure is the number of base pairs that occur in one complete turn of the helix.
Base Pairs Per Turn
- The correct answer to how many base pairs are present in every helical turn is 10.4.
- This value represents the average number of base pairs that participate in a single complete turn of the helical structure of DNA.
Significance of 10.4 Base Pairs
- The number 10.4 is derived from the helical structure of B-DNA, which is the most common form of DNA found in living organisms.
- Each helical turn spans approximately 34 angstroms (3.4 nanometers) in length, making the compact structure of DNA efficient for storage and replication.
Implications of Base Pair Count
- Understanding the number of base pairs per turn is crucial for various biological processes, including DNA replication and transcription.
- The uniformity of base pairs per turn aids in the stability and predictability of DNA interactions with proteins and enzymes.
Conclusion
- The average of 10.4 base pairs in each helical turn showcases the intricate design of DNA, allowing it to fulfill its roles in genetics and cellular function efficiently. This knowledge is foundational in molecular biology, genetics, and biochemistry studies.
Which one of the following statement is INCORRECT for Z-DNA?- a)Left-handed DNA
- b)Mostly found in alternating purine-pyrimidine sequences
- c)Only one deep, narrow groove
- d)Anti glycosidic bond conformation
Correct answer is option 'D'. Can you explain this answer?
Which one of the following statement is INCORRECT for Z-DNA?
a)
Left-handed DNA
b)
Mostly found in alternating purine-pyrimidine sequences
c)
Only one deep, narrow groove
d)
Anti glycosidic bond conformation
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Everly Young answered |
Incorrect Statement for Z-DNA:
Z-DNA is a unique form of DNA with distinct structural features that differentiate it from the more common B-DNA. One of the statements provided is incorrect for Z-DNA:
Anti glycosidic bond conformation:
- The incorrect statement is that Z-DNA has an anti glycosidic bond conformation. In reality, Z-DNA actually has a syn glycosidic bond conformation. This means that the nucleotide bases are oriented in a way that allows for a syn conformation of the glycosidic bond between the sugar and the base.
Other Characteristics of Z-DNA:
- Left-handed DNA: Z-DNA is indeed a left-handed helical form of DNA, which is different from the more common right-handed B-DNA.
- Mostly found in alternating purine-pyrimidine sequences: Z-DNA is typically found in DNA sequences that alternate between purine (adenine and guanine) and pyrimidine (cytosine and thymine) bases.
- Only one deep, narrow groove: Z-DNA has a single deep, narrow major groove and a shallow minor groove, which is different from the major and minor groove combination found in B-DNA.
In conclusion, the incorrect statement about Z-DNA is that it has an anti glycosidic bond conformation, when in fact it has a syn glycosidic bond conformation.
Z-DNA is a unique form of DNA with distinct structural features that differentiate it from the more common B-DNA. One of the statements provided is incorrect for Z-DNA:
Anti glycosidic bond conformation:
- The incorrect statement is that Z-DNA has an anti glycosidic bond conformation. In reality, Z-DNA actually has a syn glycosidic bond conformation. This means that the nucleotide bases are oriented in a way that allows for a syn conformation of the glycosidic bond between the sugar and the base.
Other Characteristics of Z-DNA:
- Left-handed DNA: Z-DNA is indeed a left-handed helical form of DNA, which is different from the more common right-handed B-DNA.
- Mostly found in alternating purine-pyrimidine sequences: Z-DNA is typically found in DNA sequences that alternate between purine (adenine and guanine) and pyrimidine (cytosine and thymine) bases.
- Only one deep, narrow groove: Z-DNA has a single deep, narrow major groove and a shallow minor groove, which is different from the major and minor groove combination found in B-DNA.
In conclusion, the incorrect statement about Z-DNA is that it has an anti glycosidic bond conformation, when in fact it has a syn glycosidic bond conformation.
Name the nitrogenous base which is found in abundance in G-quadruplex?- a)Adenine
- b)Guanine
- c)Cytosine
- d)Thymine
Correct answer is option 'B'. Can you explain this answer?
Name the nitrogenous base which is found in abundance in G-quadruplex?
a)
Adenine
b)
Guanine
c)
Cytosine
d)
Thymine
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Orion Classes answered |
When nucleic acid sequences are rich in guanine and can form four-stranded structure, it will term as G-quadruplex. It is a square arrangement of guanine, stabilized by hoogsteen hydrogen bonding.
In what direction is DNA synthesized when catalyzed by either DNA polymerase or reverse transcriptase?- a)DNA polymerase catalyzes the synthesis of DNA in the 5’→3’ direction, while reverse transcriptase catalyzes the synthesis of DNA in the 3’→5’ direction
- b)Both DNA polymerase and reverse transcriptase catalyze the synthesis of DNA in the 5’ to 3’ direction
- c)DNA polymerase catalyzes the synthesis of DNA in the 3’→5’ direction, while reverse transcriptase catalyzes the synthesis of DNA in the 5’→3’ direction
- d)Both DNA polymerase and reverse transcriptase catalyze the synthesis of DNA in the 3’ to 5’ direction
Correct answer is option 'B'. Can you explain this answer?
In what direction is DNA synthesized when catalyzed by either DNA polymerase or reverse transcriptase?
a)
DNA polymerase catalyzes the synthesis of DNA in the 5’→3’ direction, while reverse transcriptase catalyzes the synthesis of DNA in the 3’→5’ direction
b)
Both DNA polymerase and reverse transcriptase catalyze the synthesis of DNA in the 5’ to 3’ direction
c)
DNA polymerase catalyzes the synthesis of DNA in the 3’→5’ direction, while reverse transcriptase catalyzes the synthesis of DNA in the 5’→3’ direction
d)
Both DNA polymerase and reverse transcriptase catalyze the synthesis of DNA in the 3’ to 5’ direction
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Elite Coaching Classes answered |
DNA polymerase is the enzyme responsible for DNA replication and DNA repair in living organisms. It catalyzes the addition of nucleotides to the growing DNA strand in the 5' to 3' direction. This means that the new DNA strand is synthesized by adding nucleotides to the 3' end of the growing strand.
Reverse transcriptase is an enzyme that catalyzes the synthesis of DNA from an RNA template. It is commonly found in retroviruses and is used in molecular biology techniques such as reverse transcription PCR (RT-PCR). Similar to DNA polymerase, reverse transcriptase also synthesizes DNA in the 5' to 3' direction, adding nucleotides to the 3' end of the growing DNA strand.
Therefore, both DNA polymerase and reverse transcriptase synthesize DNA in the 5' to 3' direction, which is the direction of DNA strand elongation.
What constitutes the phosphodiester bonds in DNA?- a)Hydrogen bonds between nucleosides
- b)Covalently linked nucleotides
- c)Hydrogen bonds between complementary strands
- d)Covalently linked amino acids
Correct answer is option 'B'. Can you explain this answer?
What constitutes the phosphodiester bonds in DNA?
a)
Hydrogen bonds between nucleosides
b)
Covalently linked nucleotides
c)
Hydrogen bonds between complementary strands
d)
Covalently linked amino acids
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Elite Coaching Classes answered |
Phosphodiester bonds are the covalent bonds that link nucleotides together in a DNA molecule. Each nucleotide consists of a phosphate group, a sugar (deoxyribose in the case of DNA), and a nitrogenous base (adenine, guanine, cytosine, or thymine in DNA). The phosphate group of one nucleotide forms a covalent bond with the sugar of the adjacent nucleotide, creating a backbone of alternating phosphate and sugar units.
The phosphodiester bond is formed through a condensation reaction, in which a molecule of water is released. The phosphate group of one nucleotide reacts with the hydroxyl group (-OH) on the 3' carbon of the sugar of the adjacent nucleotide, forming a phosphodiester bond and linking the two nucleotides together.
These covalent bonds between nucleotides create a stable backbone in DNA and contribute to the overall stability and integrity of the molecule. Hydrogen bonds, on the other hand, play a role in the pairing of complementary bases (A-T and G-C) between the two strands of DNA.
At what point during normal DNA replication is genetic material lost from the telomeres?- a)Enzymatic action of telomerase
- b)“Unzipping” by DNA helicase
- c)Attachment of DNA polymerase to the leading strand
- d)Joining of adjacent Okazaki fragments
Correct answer is option 'D'. Can you explain this answer?
At what point during normal DNA replication is genetic material lost from the telomeres?
a)
Enzymatic action of telomerase
b)
“Unzipping” by DNA helicase
c)
Attachment of DNA polymerase to the leading strand
d)
Joining of adjacent Okazaki fragments
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Elite Coaching Classes answered |
Telomeres are repetitive DNA sequences found at the ends of chromosomes. During DNA replication, the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments. These fragments are then joined together by the enzyme DNA ligase. However, because the lagging strand synthesis starts away from the telomeres, a small portion of the telomeric DNA is not replicated during each round of DNA replication.
Over time, this loss of genetic material from the telomeres can lead to the shortening of the chromosomes. Telomerase, an enzyme that contains its own RNA template, can counteract this shortening by adding repetitive DNA sequences to the telomeres. This occurs during the enzymatic action of telomerase, which extends the telomeric DNA and maintains its length. However, telomerase activity is not present in all cell types and is particularly active in stem cells and certain cancer cells.
Therefore, while telomerase can help to counteract the loss of genetic material from telomeres, the actual loss occurs during the joining of adjacent Okazaki fragments.
A point mutation within what functional division of a DNA sequence would be most likely to ultimately result in the production of proteins which differ from the non-mutated form by only a single amino acid?- a)Exons
- b)Introns
- c)Centromeres
- d)Telomeres
Correct answer is option 'A'. Can you explain this answer?
A point mutation within what functional division of a DNA sequence would be most likely to ultimately result in the production of proteins which differ from the non-mutated form by only a single amino acid?
a)
Exons
b)
Introns
c)
Centromeres
d)
Telomeres
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Elite Coaching Classes answered |
Exons are the functional regions of DNA that contain coding sequences for protein synthesis. They are transcribed into mRNA and eventually translated into amino acids to form proteins. A point mutation within an exon can lead to a change in the coding sequence of the mRNA, which can result in the production of a protein with a different amino acid sequence.
In contrast, introns are non-coding regions of DNA that are transcribed into mRNA but are later removed through a process called splicing. Mutations within introns generally do not directly affect the amino acid sequence of the resulting protein.
Centromeres and telomeres are specialized DNA sequences involved in chromosome structure and stability, but they do not contain coding sequences for protein synthesis. Mutations in these regions are less likely to directly impact the amino acid sequence of proteins.
Which of the following enzymes is NOT involved in DNA replication?- a)Primase
- b)DNA ligase
- c)RNA polymerase
- d)Telomerase
Correct answer is option 'C'. Can you explain this answer?
Which of the following enzymes is NOT involved in DNA replication?
a)
Primase
b)
DNA ligase
c)
RNA polymerase
d)
Telomerase
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Elite Coaching Classes answered |
During DNA replication, the strands are prepared by topoisomerases to relieve torsional strain. At the replication fork, primase, choice (A), creates a primer for the initiation of replication, which is followed by DNA polymerase. On the lagging strand, Okazaki fragments form which are joined by DNA ligase, choice (C). After the chromosome has been processed, the ends, called telomeres, are replicated with the assistance of the enzyme telomerase, choice (D). RNA polymerase, distinct from primase, is responsible for transcription.
Which of the following statements regarding differences between DNA and RNA is FALSE?- a)DNA is double-stranded, whereas RNA is single-stranded.
- b)DNA uses the nitrogenous base thymine; RNA uses uracil.
- c)The sugar in DNA is deoxyribose; the sugar in RNA is ribose.
- d)DNA strands replicate in a 5′ to 3′ direction, whereas RNA is synthesized in a 3′ to 5′ direction.
Correct answer is option 'D'. Can you explain this answer?
Which of the following statements regarding differences between DNA and RNA is FALSE?
a)
DNA is double-stranded, whereas RNA is single-stranded.
b)
DNA uses the nitrogenous base thymine; RNA uses uracil.
c)
The sugar in DNA is deoxyribose; the sugar in RNA is ribose.
d)
DNA strands replicate in a 5′ to 3′ direction, whereas RNA is synthesized in a 3′ to 5′ direction.
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Elite Coaching Classes answered |
Because we are looking for the false statement, we have to read each choice to eliminate those that are true or find one that is overtly false. Let’s quickly review the main differences between DNA and RNA. DNA is double-stranded, with a deoxyribose sugar and the nitrogenous bases A, T, C, and G. RNA, on the other hand, is usually single-stranded, with a ribose sugar and the bases A, U, C, and G. Choice (D) is false because both DNA replication and RNA synthesis proceed in a 5′ to 3′ direction.
The stability and formation of G-quadruplex depends on __________- a)Monovalent cation
- b)Divalent cation
- c)Bivalent cation
- d)Pentavalent ion
Correct answer is option 'A'. Can you explain this answer?
The stability and formation of G-quadruplex depends on __________
a)
Monovalent cation
b)
Divalent cation
c)
Bivalent cation
d)
Pentavalent ion
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Orion Classes answered |
A monovalent cation is responsible for the stability of G-quadruplex as it is present in the center of the tetrad. It can be formed in either DNA or RNA.
Which of this factor is not responsible for thermal denaturation of DNA?- a)PH
- b)Temperature
- c)Ionic strength
- d)Humidity
Correct answer is option 'D'. Can you explain this answer?
Which of this factor is not responsible for thermal denaturation of DNA?
a)
PH
b)
Temperature
c)
Ionic strength
d)
Humidity
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Orion Classes answered |
When DNA duplex is laid open to the specific conditions like temperature, pH, or ionic strength it will interrupt the hydrogen bond between strands and they are no longer held together. After denaturation, the strand separates as individual coils and the double helix is denatured.
What is the role of DNA Ligase in DNA replication?- a)To unwind the DNA double helix
- b)To synthesize RNA primers
- c)To seal gaps between Okazaki fragments
- d)To proofread newly synthesized DNA
Correct answer is option 'C'. Can you explain this answer?
a)
To unwind the DNA double helix
b)
To synthesize RNA primers
c)
To seal gaps between Okazaki fragments
d)
To proofread newly synthesized DNA
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Elite Coaching Classes answered |
DNA Ligase plays a crucial role in sealing the gaps between Okazaki fragments on the lagging strand during DNA replication.
This enzyme ensures the continuity of the DNA strand by forming phosphodiester bonds between adjacent nucleotides.
This enzyme ensures the continuity of the DNA strand by forming phosphodiester bonds between adjacent nucleotides.
Which type of DNA polymerase is primarily responsible for mitochondrial DNA synthesis?- a)DNA Polymerase α
- b)DNA Polymerase β
- c)DNA Polymerase γ
- d)DNA Polymerase δ
Correct answer is option 'C'. Can you explain this answer?
a)
DNA Polymerase α
b)
DNA Polymerase β
c)
DNA Polymerase γ
d)
DNA Polymerase δ
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Elite Coaching Classes answered |
DNA Polymerase γ is primarily responsible for synthesizing mitochondrial DNA.
This enzyme is crucial for maintaining the integrity of the mitochondrial genome, which is essential for cellular energy production.
This enzyme is crucial for maintaining the integrity of the mitochondrial genome, which is essential for cellular energy production.
Where within the eukaryotic cell might a drug which exclusively binds to tRNA binding sites exert its effects?- a)The cytosol
- b)The lysosome
- c)The mitochondrial inner membrane
- d)The nucleus
Correct answer is option 'A'. Can you explain this answer?
Where within the eukaryotic cell might a drug which exclusively binds to tRNA binding sites exert its effects?
a)
The cytosol
b)
The lysosome
c)
The mitochondrial inner membrane
d)
The nucleus
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Elite Coaching Classes answered |
tRNA binding sites are primarily located in the cytosol of eukaryotic cells. The cytosol is the fluid portion of the cytoplasm, which is the region between the cell membrane and the nucleus. It is the site where many cellular processes occur, including protein synthesis.
During protein synthesis, tRNA molecules bind to ribosomes in the cytosol and deliver specific amino acids to the growing polypeptide chain based on the codons on the mRNA template. The binding of tRNA to the ribosome occurs in the cytosol, where the actual process of translation takes place.
If a drug exclusively binds to tRNA binding sites, it would likely exert its effects in the cytosol by interfering with the binding of tRNA to ribosomes or by disrupting the translation process
Restriction endonucleases are used for which of the following?
I. Gene therapy
II. Southern blotting
III. DNA repair- a)I only
- b)II only
- c)II and III only
- d)I, II, and III
Correct answer is option 'D'. Can you explain this answer?
Restriction endonucleases are used for which of the following?
I. Gene therapy
II. Southern blotting
III. DNA repair
I. Gene therapy
II. Southern blotting
III. DNA repair
a)
I only
b)
II only
c)
II and III only
d)
I, II, and III
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Elite Coaching Classes answered |
Endonucleases are enzymes that cut DNA. They are used by the cell for DNA repair. They are also used by scientists during DNA analysis, as restriction enzymes are endonucleases. Restriction enzymes are used to cleave DNA before electrophoresis and Southern blotting, and to introduce a gene of interest into a viral vector for gene therapy.
Which of the following biomolecules is LEAST likely to contain an aromatic ring?- a)Proteins
- b)Purines
- c)Carbohydrates
- d)Pyrimidines
Correct answer is option 'C'. Can you explain this answer?
Which of the following biomolecules is LEAST likely to contain an aromatic ring?
a)
Proteins
b)
Purines
c)
Carbohydrates
d)
Pyrimidines
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Elite Coaching Classes answered |
Aromatic rings must contain conjugated π electrons, which require alternating single and multiple bonds, or lone pairs. In carbohydrate ring structures, only single bonds are present, thus preventing aromaticity. Nucleic acids contain aromatic heterocycles, while proteins will generally contain at least one aromatic amino acid.
Which association between complementary bases would require the most energy to break (has the highest bond dissociation energy)?- a)A:U
- b)All are equal
- c)A:T
- d)G:C
Correct answer is option 'D'. Can you explain this answer?
Which association between complementary bases would require the most energy to break (has the highest bond dissociation energy)?
a)
A:U
b)
All are equal
c)
A:T
d)
G:C
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Elite Coaching Classes answered |
In DNA and RNA, complementary base pairs are formed through hydrogen bonding between specific nucleotide bases. The bond dissociation energy refers to the energy required to break the hydrogen bonds between the base pairs.
In DNA, the complementary base pairs are A (adenine) with T (thymine) and G (guanine) with C (cytosine). In RNA, the base T is replaced by U (uracil).
Among the given options, the G:C base pair would require the most energy to break because it forms three hydrogen bonds, while the other base pairs form only two hydrogen bonds. The additional hydrogen bond in the G:C base pair increases the strength of the interaction between the bases, resulting in a higher bond dissociation energy.
Therefore, the association between G:C base pair would require the most energy to break compared to the other complementary base pairs.
What happens to the RNA primers after DNA synthesis in prokaryotes?- a)They are incorporated into the DNA
- b)They are removed and replaced with DNA
- c)They are left in place
- d)They are converted into proteins
Correct answer is option 'B'. Can you explain this answer?
a)
They are incorporated into the DNA
b)
They are removed and replaced with DNA
c)
They are left in place
d)
They are converted into proteins
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Elite Coaching Classes answered |
In prokaryotes, RNA primers are removed and replaced with DNA after DNA synthesis is complete.
DNA Polymerase I plays a key role in this process by removing the RNA primers and filling in the gaps with DNA nucleotides.
DNA Polymerase I plays a key role in this process by removing the RNA primers and filling in the gaps with DNA nucleotides.
Which protein prevents the re-annealing of DNA strands during replication?- a)DNA Polymerase
- b)Helicase
- c)Single Strand Binding (SSB) Protein
- d)DNA Ligase
Correct answer is option 'C'. Can you explain this answer?
a)
DNA Polymerase
b)
Helicase
c)
Single Strand Binding (SSB) Protein
d)
DNA Ligase
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Elite Coaching Classes answered |
Single Strand Binding (SSB) Protein prevents the re-annealing of separated DNA strands during replication.
By binding to single-stranded DNA, SSB proteins stabilize the strands and keep them apart for effective replication to occur.
By binding to single-stranded DNA, SSB proteins stabilize the strands and keep them apart for effective replication to occur.
Pyrimidine dimers resulting from UV light damage to DNA are removed from sequences via the action of what class of enzymes?- a)Polymerases
- b)Helicases
- c)Ligases
- d)Endonucleases
Correct answer is option 'D'. Can you explain this answer?
Pyrimidine dimers resulting from UV light damage to DNA are removed from sequences via the action of what class of enzymes?
a)
Polymerases
b)
Helicases
c)
Ligases
d)
Endonucleases
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Elite Coaching Classes answered |
Pyrimidine dimers are a type of DNA damage that occurs when adjacent pyrimidine bases (thymine or cytosine) on the same DNA strand form covalent bonds with each other due to exposure to ultraviolet (UV) light. These dimers can distort the DNA structure and interfere with normal DNA replication and transcription.
To repair pyrimidine dimers, a class of enzymes called endonucleases is involved. Endonucleases are responsible for cleaving the damaged DNA strand at specific sites near the pyrimidine dimer. This creates a gap in the DNA molecule, allowing for the removal of the damaged section.
After the damaged DNA segment is removed, other DNA repair enzymes, such as DNA polymerases, helicases, and ligases, come into play to fill in the gap with new nucleotides and seal the DNA backbone, restoring the integrity of the DNA sequence.
However, specifically for the removal of pyrimidine dimers, it is the action of endonucleases that in
What is the term given to the supercoiling of circular DNA?- a)Twist number
- b)Linking number
- c)Writhe number
- d)Cross-linking
Correct answer is option 'B'. Can you explain this answer?
What is the term given to the supercoiling of circular DNA?
a)
Twist number
b)
Linking number
c)
Writhe number
d)
Cross-linking
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Orion Classes answered |
Linking number defines the no. of times one strand crosses other in closed circular DNA. It is the sum of twist number (total number of helical turn) and writhe number (supercoiling in the helix).
Lk = Tw + Wr.
Lk = Tw + Wr.
Which of them is used to introduce negative supercoiling in DNA?- a)Type 1 topoisomerase
- b)Ethidium bromide
- c)Gyrase/ type 2 topoisomerase
- d)SYBR gold
Correct answer is option 'C'. Can you explain this answer?
Which of them is used to introduce negative supercoiling in DNA?
a)
Type 1 topoisomerase
b)
Ethidium bromide
c)
Gyrase/ type 2 topoisomerase
d)
SYBR gold
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Orion Classes answered |
Type 1 topoisomerase break only one strand of DNA while gyrase works on both the strands, it breaks and reseal both DNA strands and introduce negative supercoils. Ethidium bromide and SYBR gold are used to stain DNA molecules.
Which of the following enzymes is primarily responsible for the continuous synthesis of the leading strand in prokaryotes?- a)DNA Polymerase I
- b)DNA Polymerase II
- c)DNA Polymerase III
- d)DNA Primase
Correct answer is option 'C'. Can you explain this answer?
a)
DNA Polymerase I
b)
DNA Polymerase II
c)
DNA Polymerase III
d)
DNA Primase
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Elite Coaching Classes answered |
DNA Polymerase III is primarily responsible for the continuous synthesis of the leading strand in prokaryotes.
This enzyme has high processivity, allowing it to add nucleotides quickly and efficiently during replication.
This enzyme has high processivity, allowing it to add nucleotides quickly and efficiently during replication.
What is meant by the term 'semiconservative' in the context of DNA replication?- a)Both strands of DNA are newly synthesized.
- b)Each new DNA molecule consists of one parent strand and one newly synthesized strand.
- c)The replication occurs in both directions from the origin.
- d)DNA strands are synthesized continuously.
Correct answer is option 'B'. Can you explain this answer?
a)
Both strands of DNA are newly synthesized.
b)
Each new DNA molecule consists of one parent strand and one newly synthesized strand.
c)
The replication occurs in both directions from the origin.
d)
DNA strands are synthesized continuously.
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Elite Coaching Classes answered |
'Semiconservative' refers to the mechanism of DNA replication where each new DNA molecule consists of one parent strand and one newly synthesized strand.
This was demonstrated in the Meselson and Stahl experiment, confirming that genetic information is preserved in half of the new DNA.
This was demonstrated in the Meselson and Stahl experiment, confirming that genetic information is preserved in half of the new DNA.
Who described the structure of DNA double helix?- a)Peter Mitchell
- b)Andre Jagendorf
- c)Ernest Uribe
- d)Watson and Crick
Correct answer is option 'D'. Can you explain this answer?
Who described the structure of DNA double helix?
a)
Peter Mitchell
b)
Andre Jagendorf
c)
Ernest Uribe
d)
Watson and Crick
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Orion Classes answered |
DNA double helix was first described in 1953 by Watson and Crick using X-ray diffraction. DNA fibers were obtained by Franklin and Wilkins. Watson, Crick, and Wilkins were awarded a noble prize in 1962.
In a single strand of a nucleic acid, nucleotides are linked by:- a)hydrogen bonds
- b)phosphodiester bonds
- c)ionic bonds
- d)van der Waals forces
Correct answer is option 'B'. Can you explain this answer?
In a single strand of a nucleic acid, nucleotides are linked by:
a)
hydrogen bonds
b)
phosphodiester bonds
c)
ionic bonds
d)
van der Waals forces
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Elite Coaching Classes answered |
Nucleotides bond together to form polynucleotides. The 3′ hydroxyl group of one nucleotide’s sugar joins the 5′ hydroxyl group of the adjacent nucleotide’s sugar by a phosphodiester bond. Hydrogen bonding, choice (A), is important for holding complementary strands together, but does not play a role in the bonds formed between adjacent nucleotides on a single strand.
Which form of DNA is described by Watson-Crick model?- a)B-DNA
- b)Z-DNA
- c)A-DNA
- d)Quadraplex DNA
Correct answer is option 'A'. Can you explain this answer?
Which form of DNA is described by Watson-Crick model?
a)
B-DNA
b)
Z-DNA
c)
A-DNA
d)
Quadraplex DNA
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Orion Classes answered |
There are many forms of DNA which are biologically important, out of which Watson-Crick double helix model describes the B form of DNA. The confirmation of DNA would depend on the hydration level, base modification etc.
The antibiotic doxycycline is known to bind and inhibit a particular ribosomal subunit to inhibit bacterial proliferation. How might this affect the 80S ribosome in human cells versus the 70S subunit in prokaryotes and why?- a)Doxycycline would inhibit human ribosome function by binding the 40S subunit, because both humans and prokaryotes share the 40S subunit
- b)Doxycycline would inhibit human ribosome function by binding the 30S subunit, because both humans and prokaryotes share the 30S subunit
- c)Doxycycline would not affect human ribosomes, because human ribosomes are made up of 60S and 40S subunits while prokaryotic ribosomes are made up of 50S and 30S subunits
- d)Doxycycline would not affect human ribosomes, because human ribosomes are made up of 30S and 50S subunits while prokaryotic ribosomes are made up of 30S and 40S subunits
Correct answer is option 'C'. Can you explain this answer?
The antibiotic doxycycline is known to bind and inhibit a particular ribosomal subunit to inhibit bacterial proliferation. How might this affect the 80S ribosome in human cells versus the 70S subunit in prokaryotes and why?
a)
Doxycycline would inhibit human ribosome function by binding the 40S subunit, because both humans and prokaryotes share the 40S subunit
b)
Doxycycline would inhibit human ribosome function by binding the 30S subunit, because both humans and prokaryotes share the 30S subunit
c)
Doxycycline would not affect human ribosomes, because human ribosomes are made up of 60S and 40S subunits while prokaryotic ribosomes are made up of 50S and 30S subunits
d)
Doxycycline would not affect human ribosomes, because human ribosomes are made up of 30S and 50S subunits while prokaryotic ribosomes are made up of 30S and 40S subunits
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Elite Coaching Classes answered |
The correct answer is C. Doxycycline would not affect human ribosomes because human ribosomes are made up of 60S and 40S subunits, while prokaryotic ribosomes are made up of 50S and 30S subunits.
Doxycycline specifically targets the bacterial ribosome and inhibits protein synthesis by binding to the 30S subunit in prokaryotes. The binding of doxycycline interferes with the bacterial ribosome's ability to read and translate mRNA, thereby inhibiting bacterial proliferation.
In eukaryotes, such as human cells, ribosomes have a different structure. They are composed of a 60S large subunit and a 40S small subunit. Since the structure of human ribosomes is different from prokaryotic ribosomes, doxycycline does not bind to or affect human ribosomes. Therefore, doxycycline is selective for inhibiting bacterial protein synthesis while having little effect on human cells.
An individual presenting with a mysterious disease affecting his connective tissues is found to have numerous defects in multiple regulatory proteins. If these proteins are characterized by highly abnormal patterns of glycosylation, to what structure might the patient’s disease most likely be attributed?- a)Lysosome
- b)Mitochondria
- c)Ribosome
- d)Golgi apparatus
Correct answer is option 'D'. Can you explain this answer?
An individual presenting with a mysterious disease affecting his connective tissues is found to have numerous defects in multiple regulatory proteins. If these proteins are characterized by highly abnormal patterns of glycosylation, to what structure might the patient’s disease most likely be attributed?
a)
Lysosome
b)
Mitochondria
c)
Ribosome
d)
Golgi apparatus
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Elite Coaching Classes answered |
The Golgi apparatus is an organelle involved in the modification, processing, and sorting of proteins and lipids in eukaryotic cells. One of its important functions is the glycosylation of proteins, which involves the attachment of sugar molecules to specific sites on proteins.
Defects in the Golgi apparatus and its glycosylation processes can lead to abnormalities in the structure and function of proteins. Abnormal patterns of glycosylation can affect the folding, stability, trafficking, and interactions of proteins, including regulatory proteins.
In the case described in the question, where the individual has a mysterious disease affecting connective tissues and defects in multiple regulatory proteins with abnormal glycosylation patterns, it suggests that the disease is most likely attributed to dysfunction or abnormalities in the Golgi apparatus. The Golgi apparatus plays a crucial role in the proper glycosylation of proteins, and abnormalities in this process can have significant consequences on protein function and ultimately lead to disease manifestations.
Which of the following DNA sequences would have the highest melting temperature?- a)CGCAACCATCCG
- b)CGCAATAATACA
- c)CGTAATAATACA
- d)CATAACAAATCA
Correct answer is option 'A'. Can you explain this answer?
Which of the following DNA sequences would have the highest melting temperature?
a)
CGCAACCATCCG
b)
CGCAATAATACA
c)
CGTAATAATACA
d)
CATAACAAATCA
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Elite Coaching Classes answered |
The melting temperature of DNA is the temperature at which a DNA double helix separates into two single strands (denatures). To do this, the hydrogen bonds linking the base pairs must be broken. Cytosine binds to guanine with three hydrogen bonds, whereas adenine binds to thymine with two hydrogen bonds. The amount of heat needed to disrupt the bonding is proportional to the number of bonds. Thus, the higher the GC-content in a DNA segment, the higher the melting point.
For a compound to be aromatic, all of the following must be true EXCEPT:- a)the molecule is cyclic.
- b)the molecule contains 4n + 2 π electrons.
- c)the molecule contains alternating single and double bonds.
- d)the molecule is planar.
Correct answer is option 'C'. Can you explain this answer?
For a compound to be aromatic, all of the following must be true EXCEPT:
a)
the molecule is cyclic.
b)
the molecule contains 4n + 2 π electrons.
c)
the molecule contains alternating single and double bonds.
d)
the molecule is planar.
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Elite Coaching Classes answered |
For a compound to be aromatic, it must be cyclic, planar, and conjugated, and contain 4n + 2 π electrons, where n is any integer. Conjugation requires that every atom in the ring have at least one unhybridized p-orbital. While most examples of aromatic compounds have alternating single and double bonds, compounds can be aromatic if they contain triple bonds as well; this would still permit at least one unhybridized p-orbital.
What is the functional relationship between codons and amino acids?- a)Many different codons may code for the same amino acid
- b)A single codon may code for many different amino acids
- c)Codons and amino acids randomly associate around a particular tRNA
- d)A given amino acid is only coded for by a single codon
Correct answer is option 'A'. Can you explain this answer?
What is the functional relationship between codons and amino acids?
a)
Many different codons may code for the same amino acid
b)
A single codon may code for many different amino acids
c)
Codons and amino acids randomly associate around a particular tRNA
d)
A given amino acid is only coded for by a single codon
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Elite Coaching Classes answered |
Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids during protein synthesis. The genetic code is degenerate, meaning that multiple codons can code for the same amino acid. This is due to the redundancy in the genetic code, where different combinations of the four nucleotides (A, U, G, and C) can specify the same amino acid.
For example, the amino acid leucine is specified by six different codons: UUA, UUG, CUU, CUC, CUA, and CUG. All of these codons code for the same amino acid, even though they have different nucleotide sequences.
This redundancy in the genetic code provides a level of error tolerance and allows for robustness in protein synthesis. It also allows for a more efficient use of the limited number of codons available in the genetic code.
What is the primary function of telomerase?- a)To synthesize RNA primers
- b)To prevent DNA from shortening during cell division
- c)To repair damaged DNA
- d)To initiate DNA replication
Correct answer is option 'B'. Can you explain this answer?
a)
To synthesize RNA primers
b)
To prevent DNA from shortening during cell division
c)
To repair damaged DNA
d)
To initiate DNA replication
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Elite Coaching Classes answered |
The primary function of telomerase is to prevent DNA from shortening during cell division.
This enzyme adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), thus preserving the genetic information from being lost during replication.
This enzyme adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), thus preserving the genetic information from being lost during replication.
What is the function of topoisomerases during DNA replication?- a)To synthesize new DNA strands
- b)To relieve torsional strain caused by unwinding DNA
- c)To bind single-stranded DNA
- d)To proofread DNA
Correct answer is option 'B'. Can you explain this answer?
a)
To synthesize new DNA strands
b)
To relieve torsional strain caused by unwinding DNA
c)
To bind single-stranded DNA
d)
To proofread DNA
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Elite Coaching Classes answered |
Topoisomerases relieve torsional strain that results from the unwinding of DNA by helicase.
By making temporary cuts in the DNA strands, these enzymes help prevent supercoiling, allowing replication to proceed smoothly.
By making temporary cuts in the DNA strands, these enzymes help prevent supercoiling, allowing replication to proceed smoothly.
What is the direction of DNA strand synthesis during replication?- a)5’ to 3’ direction
- b)3’ to 5’ direction
- c)Bidirectional
- d)Random direction
Correct answer is option 'A'. Can you explain this answer?
a)
5’ to 3’ direction
b)
3’ to 5’ direction
c)
Bidirectional
d)
Random direction
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Elite Coaching Classes answered |
DNA strands are synthesized in the 5’ to 3’ direction.
This means that nucleotides are added to the growing strand at the 3’ end, which is crucial for maintaining the integrity of the DNA structure and function.
This means that nucleotides are added to the growing strand at the 3’ end, which is crucial for maintaining the integrity of the DNA structure and function.
What are Okazaki fragments?- a)Short sequences of RNA primers
- b)Segments of newly synthesized DNA on the leading strand
- c)Short segments of DNA synthesized on the lagging strand
- d)Fragments of RNA used in transcription
Correct answer is option 'C'. Can you explain this answer?
a)
Short sequences of RNA primers
b)
Segments of newly synthesized DNA on the leading strand
c)
Short segments of DNA synthesized on the lagging strand
d)
Fragments of RNA used in transcription
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Elite Coaching Classes answered |
Okazaki fragments are short segments of newly synthesized DNA on the lagging strand during DNA replication.
These fragments are synthesized discontinuously and later joined together by DNA ligase to form a complete DNA strand.
These fragments are synthesized discontinuously and later joined together by DNA ligase to form a complete DNA strand.
Which enzyme is responsible for synthesizing RNA primers during DNA replication?- a)DNA Polymerase
- b)DNA Primase
- c)Helicase
- d)DNA Ligase
Correct answer is option 'B'. Can you explain this answer?
a)
DNA Polymerase
b)
DNA Primase
c)
Helicase
d)
DNA Ligase
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Elite Coaching Classes answered |
DNA Primase is the enzyme that synthesizes RNA primers during DNA replication.
These primers are essential for initiating DNA synthesis, as DNA polymerases require a free 3’ hydroxyl group to begin adding nucleotides.
These primers are essential for initiating DNA synthesis, as DNA polymerases require a free 3’ hydroxyl group to begin adding nucleotides.
What is the primary function of DNA replication in living cells?- a)To repair damaged DNA
- b)To copy DNA so that each new cell receives genetic information
- c)To synthesize proteins from RNA
- d)To facilitate cell division by creating new cells
Correct answer is option 'B'. Can you explain this answer?
a)
To repair damaged DNA
b)
To copy DNA so that each new cell receives genetic information
c)
To synthesize proteins from RNA
d)
To facilitate cell division by creating new cells
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Elite Coaching Classes answered |
The primary function of DNA replication is to copy DNA so that each new cell receives the same genetic information as the parent cell.
This process ensures the continuity of genetic information across generations, which is essential for growth and reproduction in living organisms.
This process ensures the continuity of genetic information across generations, which is essential for growth and reproduction in living organisms.
During which phase of the cell cycle does DNA replication occur?- a)G1 phase
- b)S phase
- c)G2 phase
- d)M phase
Correct answer is option 'B'. Can you explain this answer?
a)
G1 phase
b)
S phase
c)
G2 phase
d)
M phase
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Elite Coaching Classes answered |
DNA replication occurs during the S phase of the cell cycle.
This phase is specifically dedicated to DNA synthesis, ensuring that each daughter cell will have an identical set of chromosomes following cell division.
This phase is specifically dedicated to DNA synthesis, ensuring that each daughter cell will have an identical set of chromosomes following cell division.
Which of the following statements is true regarding the proofreading ability of DNA polymerases?- a)Only DNA Polymerase III has proofreading capability.
- b)All DNA polymerases possess proofreading activity.
- c)Proofreading occurs only during DNA repair.
- d)Proofreading is not essential for DNA replication.
Correct answer is option 'B'. Can you explain this answer?
a)
Only DNA Polymerase III has proofreading capability.
b)
All DNA polymerases possess proofreading activity.
c)
Proofreading occurs only during DNA repair.
d)
Proofreading is not essential for DNA replication.
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Elite Coaching Classes answered |
All DNA polymerases possess proofreading activity, which is essential for maintaining the fidelity of DNA replication.
This activity allows for the identification and correction of errors, significantly reducing the mutation rate during DNA synthesis.
This activity allows for the identification and correction of errors, significantly reducing the mutation rate during DNA synthesis.
Which of the following is an ethical concern of gene sequencing?- a)Gene sequencing is invasive, thus the potential health risks must be thoroughly explained.
- b)Gene sequencing impacts relatives, thus privacy concerns may be raised.
- c)Gene sequencing is very inaccurate, which increases anxiety related to findings.
- d)Gene sequencing can provide false-negative results, giving a false sense of security.
Correct answer is option 'B'. Can you explain this answer?
Which of the following is an ethical concern of gene sequencing?
a)
Gene sequencing is invasive, thus the potential health risks must be thoroughly explained.
b)
Gene sequencing impacts relatives, thus privacy concerns may be raised.
c)
Gene sequencing is very inaccurate, which increases anxiety related to findings.
d)
Gene sequencing can provide false-negative results, giving a false sense of security.
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Elite Coaching Classes answered |
One of the primary ethical concerns related to gene sequencing is the issue of consent and privacy. Because genetic screening provides information on direct relatives, there are potential violations of privacy in communicating this information to family members who may be at risk. There are not significant physical risks, eliminating choice (A), and gene sequencing is fairly accurate, eliminating choices (C) and (D).
Why might uracil be excluded from DNA but NOT RNA?- a)Uracil is much more difficult to synthesize than thymine.
- b)Uracil binds adenine too strongly for replication.
- c)Cytosine degradation results in uracil.
- d)Uracil is used as a DNA synthesis activator.
Correct answer is option 'C'. Can you explain this answer?
Why might uracil be excluded from DNA but NOT RNA?
a)
Uracil is much more difficult to synthesize than thymine.
b)
Uracil binds adenine too strongly for replication.
c)
Cytosine degradation results in uracil.
d)
Uracil is used as a DNA synthesis activator.
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Elite Coaching Classes answered |
One common DNA mutation is the transition from cytosine to uracil in the presence of heat. DNA repair enzymes recognize uracil and correct this error by excising the base and inserting cytosine. RNA exists only transiently in the cell, such that cytosine degradation is insignificant. Were uracil to be used in DNA under normal circumstances, it would be impossible to tell if a base should be uracil or if it is a damaged cytosine nucleotide.
How is cDNA best characterized?- a)cDNA results from a DNA transcript with noncoding regions removed.
- b)cDNA results from the reverse transcription of processed mRNA.
- c)cDNA is the abbreviation for deoxycytosine.
- d)cDNA is the circular DNA molecule that forms the bacterial genome.
Correct answer is option 'B'. Can you explain this answer?
How is cDNA best characterized?
a)
cDNA results from a DNA transcript with noncoding regions removed.
b)
cDNA results from the reverse transcription of processed mRNA.
c)
cDNA is the abbreviation for deoxycytosine.
d)
cDNA is the circular DNA molecule that forms the bacterial genome.
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Elite Coaching Classes answered |
cDNA (complementary DNA) is formed from a processed mRNA strand by reverse transcription. cDNA is used in DNA libraries and contains only the exons of genes that are transcriptionally active in the sample tissue.
The third strand of triple helix is paired in which scheme?- a)Hoogsteen base pair scheme
- b)Intermolecular base pair scheme
- c)Intramolecular base pair scheme
- d)G-quartet scheme
Correct answer is option 'A'. Can you explain this answer?
The third strand of triple helix is paired in which scheme?
a)
Hoogsteen base pair scheme
b)
Intermolecular base pair scheme
c)
Intramolecular base pair scheme
d)
G-quartet scheme
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Orion Classes answered |
Triple helix formed by three strands polypurine, polypyrimidine and the third strand which lay in the major groove of DNA and makes a hydrogen bond to duplex. The third strand is paired in hoogsteen base pairing scheme where the central strand is purine rich.
What is the consequence of telomere shortening in somatic cells?- a)Enhanced DNA repair
- b)Cellular aging
- c)Increased cellular division
- d)Improved genomic stability
Correct answer is option 'B'. Can you explain this answer?
a)
Enhanced DNA repair
b)
Cellular aging
c)
Increased cellular division
d)
Improved genomic stability
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Elite Coaching Classes answered |
Telomere shortening in somatic cells is associated with cellular aging.
As telomeres shorten with each cell division, the ability of cells to divide diminishes, leading to senescence and contributing to the aging process.
As telomeres shorten with each cell division, the ability of cells to divide diminishes, leading to senescence and contributing to the aging process.
Which type of DNA repair mechanism involves the removal of damaged bases and replacement with correct ones?- a)Nucleotide Excision Repair (NER)
- b)Mismatch Repair (MMR)
- c)Base Excision Repair (BER)
- d)Homologous Recombination (HR)
Correct answer is option 'C'. Can you explain this answer?
a)
Nucleotide Excision Repair (NER)
b)
Mismatch Repair (MMR)
c)
Base Excision Repair (BER)
d)
Homologous Recombination (HR)
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Elite Coaching Classes answered |
Base Excision Repair (BER) involves the removal of damaged bases and their replacement with the correct ones.
This repair mechanism is critical for correcting small, non-helix-distorting base lesions, maintaining the overall integrity of the DNA.
This repair mechanism is critical for correcting small, non-helix-distorting base lesions, maintaining the overall integrity of the DNA.
Which rule dictates the pairing of bases during DNA replication?- a)The Chargaff's rule
- b)The Watson-Crick rule
- c)The base pairing rule
- d)The semiconservative rule
Correct answer is option 'C'. Can you explain this answer?
a)
The Chargaff's rule
b)
The Watson-Crick rule
c)
The base pairing rule
d)
The semiconservative rule
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Elite Coaching Classes answered |
The base pairing rule states that adenine pairs with thymine and cytosine pairs with guanine during DNA replication.
This ensures that the genetic information is accurately copied from the parent strand to the daughter strand.
This ensures that the genetic information is accurately copied from the parent strand to the daughter strand.
Chapter doubts & questions for DNA Replication (BIO) - MCAT Biological and Biochemical Foundations 2025 is part of MCAT exam preparation. The chapters have been prepared according to the MCAT exam syllabus. The Chapter doubts & questions, notes, tests & MCQs are made for MCAT 2025 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests here.
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