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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.
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.
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
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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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.
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.
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.
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