CBSE 2024 · Region 2 · Set 3 · Q31 · 5 marks
Answer the following questions that are based on "Hershey and Chase" experiment using E. coli and bacteriophage :(i)Why did they use radioactive sulphur $\displaystyle { }^{35} \mathrm{~S}$ and radioactive phosphorus $\displaystyle { }^{32} \mathrm{P}$ in their respective culture media for growing E. coli population which subsequently were infected by bacteriophage ?(ii)State the purpose of their using the following :(1)Blender(2)Centrifuge(iii)Write the observations they made during the course of their experiment.(iv)Based on the results, write the conclusion they arrived at the end of their experiment.(i)Describe the process of transcription in prokaryotes with respect to initiation, elongation and termination.(ii)Write how many types of RNA polymerases are used in transcription in(1)Prokaryotes,(2)Eukaryotes.
Answer the following questions that are based on "Hershey and Chase" experiment using E. coli and bacteriophage :
(i)
Why did they use radioactive sulphur $\displaystyle { }^{35} \mathrm{~S}$ and radioactive phosphorus $\displaystyle { }^{32} \mathrm{P}$ in their respective culture media for growing E. coli population which subsequently were infected by bacteriophage ?
(ii)
State the purpose of their using the following :
(1)
Blender
(2)
Centrifuge
(iii)
Write the observations they made during the course of their experiment.
(iv)
Based on the results, write the conclusion they arrived at the end of their experiment.
(i)
Describe the process of transcription in prokaryotes with respect to initiation, elongation and termination.
(ii)
Write how many types of RNA polymerases are used in transcription in
(1)
Prokaryotes,
(2)
Eukaryotes.
Marking-scheme solution
(i)
• Since Sulphur is component of protein so they used radioactive
Sulphur to label protein coat of the virus
• Since Phosphorus is the component of the DNA so they used
radioactive Phosphorus to label DNA.
(ii)(1)
To remove viral coats from bacteria or E.coli by agitating..
(2)
The viral particles were separated from bacteria or E.coli by spinning in a centrifuge.
(iii)
No radioactive S35 detected in the cells but detected in the
supernatant in case of radioactive S35 labelled protein capsule of bacteriophage
Radioactive P32 detected in cells but not in the supernatant in case
of viruses having radioactive P32 labelled DNA.
(iv)
DNA is the genetic material.
(i)
• Initiation-DNA dependent RNA polymerase attaches at $\displaystyle 3$’-end
of the DNA template using sigma factor.
• Elongation- by using nucleotide triphosphates as substrate
polymerization in template dependent fashion occurs by following rule of complementarity.
• Termination-on reaching terminator region polymerase binds
with rho factor leads to separation of nascent RNA and polymerase.
(ii)(1)
one in prokaryotes
(2)
three in eukaryotes
Molecular Basis of InheritanceThe Search for Genetic MaterialUnderstandlong_answermedium
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CBSE Class 12 Biology past-paper question from the 2024board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.