Question

40 S subunit of mammalian ribosomes contain

• A. 5S RNA
• B. 5.8 S RNA
• C. 18S RNA
• D. 28S RNA

Hint:

Remember the matching pairs:
- 40S subunit is associated with 18S rRNA.
- 60S subunit is associated with 28S, 5.8S, and 5S rRNAs.
- (In prokaryotes, the 30S subunit is associated with 16S rRNA).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Ribosomal subunits are assembled from specific, highly conserved rRNA molecules of defined sedimentation coefficients (S-values).

Step 2: Detailed Explanation:
In mammalian (eukaryotic) cells, the 80S ribosome is composed of:
- 60S Large Subunit: Contains three distinct rRNA molecules: 28S rRNA, 5.8S rRNA, and 5S rRNA. This rules out (A), (B), and (D).
- 40S Small Subunit: Contains a single structural rRNA molecule: 18S rRNA (written as 18S RNA in option 3).

Step 3: Final Answer:
The correct option is 3, which corresponds to 18S RNA.