All questions of Daily Practice & Tests for NEET Exam

RNA polymerase moves along the template strand, synthesising an mRNA molecule. In prokaryotes RNA polymerase is a holoenzyme consisting of a number of subunits, including a sigma factor (transcription factor) that recognises the promoter. In eukaryotes there are three RNA polymerases: I, II and III. The process includes a proofreading mechanism.

NUCLEOBASE(it is base pairing between nitrogen bases i.e A ,T,G,C) therefore  it does not affect the length of DNA where as sugar phosphate bond is the back bone of DNA therefore they both affect the length of DNA

Ribosomes are site of protein synthesis and are known as protein factory

The ability of a gene to have multiple phenotypic effects because it influences a number of characters simultaneously is known as pleiotropy. The gene having a multiple phenotypic effect because of its ability to control expression of two or more characters is called pleiotropic gene. In human beings pleiotropy is exhibited by syndromes called sickle cell anaemia and phenylketonuria.

The discovery that DNA has genetic properties was first revealed by Oswald Avery and his team of scientists in 1944. Avery was a molecular biologist who worked at the Rockefeller Institute for Medical Research in New York City.

Experiment
Avery and his team conducted a series of experiments to determine whether DNA was the genetic material responsible for the transformation of bacteria. They used two strains of Streptococcus pneumoniae, one that was virulent (able to cause disease) and one that was non-virulent. The virulent strain had a capsule made of a complex sugar that protected it from the immune system, while the non-virulent strain lacked this capsule and was easily destroyed by the immune system.

Results
Avery and his team extracted various biochemical components from the virulent strain of bacteria, including proteins, lipids, RNA, and DNA. They then mixed each of these components with the non-virulent strain to see if they could induce transformation. Only the DNA extract was able to transform the non-virulent strain into a virulent one, proving that DNA was the genetic material responsible for the transformation.

Conclusion
Avery's discovery was groundbreaking because it showed that DNA, which was previously thought to be a simple molecule with no biological significance, was in fact the carrier of genetic information. This discovery paved the way for the development of the field of molecular biology and our current understanding of genetics.

Since The stop codons are UAA, UAG, and UGA.  They encode no amino acid. The ribosome pauses and falls off the mRNA.

Chromosomes are thread like structures of DNA and proteins that carry genetic information of organisms in the form of genes. The human chromosomes with least number of genes is Your chromosome.
Option " C " is correct answer.

Read ncert

Bacteria can take up forigen DNA in a process called transformation. It occurs after restriction digest and ligation and transfers newly made plasmid to bacteria.
Bacteria with a plasmid are antibiotic resistant, and each will form a colony.

Meselson and Stahl prove experimentally semi conservation of DNA replication not say but structure of DNA.

Genetic Fingerprinting

Genetic fingerprinting or DNA fingerprinting is a technique used to identify individuals based on their unique DNA profiles. PCR and Restriction Fragment Length Polymorphism (RFLP) are two commonly used methods for genetic fingerprinting.

Polymerase Chain Reaction (PCR)

PCR is a powerful technique used to amplify a specific DNA sequence. It involves a series of repeated cycles of denaturation, annealing, and extension, resulting in the exponential amplification of a specific DNA fragment. PCR is used in genetic fingerprinting to amplify DNA from a sample, such as blood or tissue, and create multiple copies of a specific DNA fragment for analysis.

Restriction Fragment Length Polymorphism (RFLP)

RFLP is a technique used to identify variations in DNA sequences between individuals. It involves the use of restriction enzymes to cut DNA at specific sites, resulting in fragments of different sizes. The resulting fragments are separated by gel electrophoresis and visualized using a staining agent. The pattern of fragment sizes is unique to each individual and can be used to identify them.

Applications of Genetic Fingerprinting

Genetic fingerprinting has a wide range of applications, including:

- Forensic investigations: DNA evidence can be used to identify suspects or victims in criminal investigations.
- Paternity testing: DNA analysis can be used to determine biological relationships, such as paternity or maternity.
- Medical diagnosis: Genetic fingerprinting can be used to diagnose genetic diseases and identify carriers of genetic mutations.
- Evolutionary studies: Genetic fingerprinting can be used to study the evolutionary relationships between different species.

Conclusion

PCR and RFLP are two powerful techniques used in genetic fingerprinting. These techniques have revolutionized the field of forensic science and have a wide range of applications in medicine, biology, and genetics.

A typical nucleosome contains 200 bp of DNA double helix wrapped(2 turns) around a core of histone octamer having two copies of each of four types of histone proteins ..H2A,H2B,H3,&H4.....H1 histone molecule lies outside the nucleosome core & seals the two turns of DNA by binding at the point where DNA enters and leaves the core..

The hybridization of probes having radioactive isotopes with various sequence of nitrogen bases with ssVNTR is called southern blotting. Southern blotting is a laboratory technique used to detect a specific DNA sequence in a blood or tissue sample. A restriction enzyme is used to cut a sample of DNA into fragments that are separated using gel electrophoresis. The DNA fragments are transferred out of the gel to the surface of a membrane. The membrane is exposed to a DNA probe labeled with a radioactive or chemical tag. If the probe binds to the membrane, then the probe sequence is present in the sample. Hence, the correct answer is option 'B'.

B is correct refer to ncert for details

Most human cells have 2 of each of the 23 homologous monoploid chromosomes, for a total of 46 chromosomes. A human cell with an extra set out of the 23 normal ones would be considered euploid. Euploid karyotypes would consequentially be a multiple of the haploid number, which in humans is 23.

In negative inducible operons, a regulatory repressor protein is normally bound to the operator, which prevents the transcription of the genes in the operon. If an inducer molecule is present, it binds to the repressor and changes its conformation so that it is unable to bind to the operator. This allows for expression of the operon. The lac operon is a negatively controlled inducible operon, where the inducer molecule is allolactose

In 1928 Griffith experiment on streptococcus pneumonia and mice

Enzymes and their Functions:

DNA polymerase: Synthesis of DNA Strands
- DNA polymerase is an enzyme responsible for the synthesis of DNA strands.
- It catalyzes the addition of nucleotides to the growing DNA strand during DNA replication.
- It reads the template DNA strand and adds complementary nucleotides to form a new DNA strand.
- DNA polymerase plays a crucial role in maintaining the integrity and fidelity of the DNA sequence during replication.

Helicase: Unwinding of DNA helix
- Helicase is an enzyme that unwinds the double-stranded DNA helix during DNA replication.
- It breaks the hydrogen bonds between the base pairs, separating the DNA strands and creating a replication fork.
- This unwinding process is necessary for DNA replication as it exposes the template strands for DNA polymerase to synthesize new strands.

Ligase: Joins together short DNA segments
- Ligase is an enzyme that joins together short DNA segments, specifically the Okazaki fragments on the lagging strand during DNA replication.
- It catalyzes the formation of phosphodiester bonds between the adjacent nucleotides, sealing the gaps and creating a continuous DNA strand.
- Ligase plays a significant role in completing the synthesis of the lagging strand during DNA replication.

Explanation:
The correct match of enzyme with its related function is option 'D' - All of these.
- DNA polymerase is responsible for the synthesis of DNA strands during DNA replication.
- Helicase unwinds the DNA helix to expose the template strands for replication.
- Ligase joins together short DNA segments, ensuring the completion of the lagging strand synthesis.
- Therefore, all three enzymes are involved in different steps of DNA replication and collectively play crucial roles in maintaining the integrity and fidelity of the DNA sequence.