Class 12 Biology - Chapter Molecular Basis of Inheritance NCERT Solutions | How did Hershey and Chase differentiate
How did Hershey and Chase differentiate between DNA and protein in their experiment while proving that DNA is the genetic material?
Hershey and Chase worked with bacteriophage and E.coli to prove that DNA is the genetic material. They used different radioactive isotopes to label DNA and protein coat of the bacteriophage.
They grew some bacteriophages on a medium containing radioactive phosphorus (32P) to identify DNA and some on a medium containing radioactive sulphur (35S) to identify protein. Then, these radioactive labelled phages were allowed to infect E.coli bacteria. After infecting, the protein coat of the bacteriophage was separated from the bacterial cell by blending and then subjected to the process of centrifugation.
Since the protein coat was lighter, it was found in the supernatant while the infected bacteria got settled at the bottom of the centrifuge tube. In case I, supematatn was found radioactive. Which shows protein did not enter in bacterial cell during infection. While in case II, Bacterial cells in pelld were radioactive as they have radioactive DNA.
Hence, it was proved that DNA is the genetic material as it was transferred from virus to bacteria.
More Questions From Class 12 Biology - Chapter Molecular Basis of Inhertance
- Q:- What is DNA fingerprinting? Mention its application.
- Q:- Differentiate between the followings:
(a) Repetitive DNA and Satellite DNA
(b) mRNA and tRNA
(c) Template strand and Coding strand - Q:- If the sequence of the coding strand in a transcription unit is written as follows:
5-ATGCATGCATGCATGCATGCATGCATGC-3
Write down the sequence of mRNA. - Q:- Explain (in one or two lines) the function of the followings:
(a) Promoter
(b) tRNA
(c) Exons - Q:-
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- Q:- List two essential roles of ribosome during translation.
- Q:- Which property of DNA double helix led Watson and Crick to hypothesise semi-conservative mode of DNA replication? Explain.
- Q:- In the medium where E. coli was growing, lactose was added, which induced the lac operon. Then, why does lac operon shut down some time after addition of lactose in the medium?
- Q:- If the sequence of one strand of DNA is written as follows:
5-ATGCATGCATGCATGCATGCATGCATGC-3
Write down the sequence of complementary strand in 5→3 direction - Q:- If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.
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Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
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(b) Endometrium
(c) Acrosome
(d) Sperm tail
(e) Fimbriae
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