✓ Board-verified
Biology · 2024 · 5 marks
CBSE 2024 · Region 2 · Set 3 · Q31
Answer the following questions that are based on "Hershey and Chase" experiment using E. coli and bacteriophage: (a) (i) Why did they use radioactive…
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
All Molecular Basis of Inheritance questions2024 question paperNCERT solutions: Molecular Basis of InheritancePractice Molecular Basis of Inheritance →
More from Molecular Basis of Inheritance
- A bacterium having radioactive thymidine in its DNA is allowed to multiply in a medium having non-radioactive thymidine for two generations. What…2026
- Assertion: Repetitive sequences are stretches of DNA sequences that are thought to have no direct coding functions. Reason (R): They shed light on…2026
- Explain how the addition of lactose in the medium regulates the switching on of the lac operon in bacteria.2025
- In a human, the average gene consists of (i) bases and the largest known human gene contains (ii) bases. Select the correct option to fill in the…2026
- In a translational unit UTRs are present at:2025
- The simplest definition of a gene in eukaryotes is - A unit of DNA that has information to mainly specify the synthesis of:2025
- Explain the processing of heterogeneous nuclear RNA (hnRNA) into a fully functional mRNA in eukaryotes. Where does this processing occur in the cell?2024
- The type of bond represented by the dotted line '-----' in a schematic polynucleotide chain is:2024
CBSE Class 12 Biology past-paper question from the 2024 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.