Long Answer TypeHow did Hershey and Chase established that DNA is transferred from virus to bacteria?
Hershey and Chase worked on bacteriophages (viruses that infect bacteria).
When a bacteriophage infects a bacterium, the viral genetic material gets attached with the bacterial genetic material and then, bacteria treats the viral genetic material as its own to synthesize more viral particles.
Hershey and Chase experiment were to discover whether it was a protein or DNA that entered the bacteria from virus. They carried out the following steps:
i. They labelled some phages with radioactive sulphur and the others with radioactive phosphorus.
ii. These radioactive phages were used to infect E. coli.
iii. Then, E.coli was blended and centrifuged to remove viral particles.
iv. It was observed that bacteria with radioactive DNA were radioactive while those with radioactive proteins lost their radioactivity.
This showed that it is the DNA that enters the bacteria from viruses and not proteins. Hence, it was concluded that DNA is the genetic material.
Short Answer TypeName the enzyme and state its property that is responsible for continuous and discontinuous replication of the two strands of a DNA molecule.
Why is the enzyme cellulase needed for isolating genetic material from plant cells and not from the animal cells?
Describe the structure of a RNA polynucleotide chain having four different types of nucleotides.
Draw a schematic diagram of a part of double stranded dinucleotide DNA chain having all the four nitrogenous bases and showing the correct polarity.
It is established that RNA is the first genetic material. Explain giving three reasons.
(a) Name the enzyme responsible for the transcription of tRNA and the amino acid the initiator tRNA gets linked with.
(b) Explain the role of initiator tRNA in initiation of protein synthesis.
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