Question

Which of the following statements are correct regarding protein synthesis in eukaryotes?
A. 3'-Cap of mRNA present.
B. Ribosomes of 80S type dissociate into 40S and 60S subunits.
C. Translation is not simultaneous with transcription.
D. Initiation codon of mRNA is recognised by anticodon of Met-tRNA.
Choose the correct answer from the options given below:

• A. A, C and D only
• B. A, B and C only
• C. B, C and D only
• D. A, B, C, D

Hint:

Remember the key differences between prokaryotic and eukaryotic protein synthesis: \textbf{Eukaryotes:} 80S ribosomes (60S+40S), 5' cap & 3' tail, monocistronic mRNA, transcription in nucleus, translation in cytoplasm (separate), initiator is Met-tRNA. \textbf{Prokaryotes:} 70S ribosomes (50S+30S), no cap/tail, polycistronic mRNA, transcription and translation are coupled, initiator is fMet-tRNA.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
The question asks to identify the correct statements about protein synthesis (translation) specifically in eukaryotic cells. This requires knowledge of the key features that distinguish eukaryotic translation from prokaryotic translation.
Step 2: Detailed Explanation:
Let's evaluate each statement:

A. 3'-Cap of mRNA present. This statement is incorrect. Eukaryotic mRNA undergoes post-transcriptional modification which includes the addition of a 7-methylguanosine cap at the 5' end, not the 3' end. The 3' end typically has a poly-A tail.

B. Ribosomes of 80S type dissociate into 40S and 60S subunits. This statement is correct. Eukaryotic cells have 80S ribosomes, which are composed of a small 40S subunit and a large 60S subunit. (The Svedberg units are not additive).

C. Translation is not simultaneous with transcription. This statement is correct. In eukaryotes, transcription occurs inside the nucleus, while translation occurs in the cytoplasm. Due to this spatial and temporal separation (and the need for mRNA processing), the two processes cannot be coupled, unlike in prokaryotes where they occur simultaneously in the cytoplasm.

D. Initiation codon of mRNA is recognised by anticodon of Met-tRNA. This statement is correct. The start codon for translation in eukaryotes is AUG, which is recognized by the anticodon of a special initiator tRNA carrying the amino acid Methionine (Met).

Step 3: Final Answer:
Statements B, C, and D are correct, while statement A is incorrect. Therefore, the correct option is the one that includes only B, C, and D.