Question

Choose the correct statements :

(i) Polycistronic mRNA is generally found in eukaryotes.

(ii) The RNA polymerase II transcribes precursor of mRNA, the hnRNA.

(iii) The process of translation of mRNA begins when the mRNA encounters the large subunit of ribosomes.

(iv) Stop codons do not have any tRNAs.

Options :

• A. (i) and (ii)
• B. (ii) and (iii)
• C. (ii) and (iv)
• D. (i), (ii) and (iv)

Hint:

Polycistronic mRNA is bacterial and the small ribosomal subunit binds mRNA first, so only (ii) and (iv) are true.

Answer 1

The Correct Option is C

Step 1: Check statement (i):
Polycistronic mRNA carries codes for more than one polypeptide.
It is found in bacteria (as in the lac operon), not generally in eukaryotes.
Eukaryotic mRNA is monocistronic. So (i) is FALSE.

Step 2: Check statement (ii):
In eukaryotes RNA polymerase II makes hnRNA, the precursor of mRNA.
hnRNA is then spliced, capped and tailed. So (ii) is TRUE.

Step 3: Check statement (iii):
Translation begins when mRNA meets the small subunit of the ribosome.
The large subunit joins afterwards. So (iii) is FALSE.

Step 4: Check statement (iv):
The stop codons UAA, UAG and UGA are not read by any tRNA.
Release factors recognise them. So (iv) is TRUE.

Final Answer:
Only (ii) and (iv) are correct, which is option (C). \[ \boxed{\text{(ii) and (iv)}} \]