Q.16 Which one of the following is true for piRNAs?
(A) piRNAs silence transposable elements in germ cells
(B) piRNA is the abbreviation of P-element interacting RNA
(C) piRNAs modify the 2′-OH of ribose with methyl group
(D) piRNA is a long non-coding RNA

PiRNAs, or PIWI-interacting RNAs, are small non-coding RNAs crucial for genome defense, particularly in germ cells. The correct answer to the multiple-choice question is option (A).​

Correct Answer

piRNAs silence transposable elements in germ cells. These 24-31 nucleotide RNAs associate with PIWI proteins to suppress transposon activity through transcriptional and post-transcriptional mechanisms, preventing genomic instability and sterility.​

Option Analysis

(A) Accurate Statement

This option correctly identifies piRNAs’ primary role in germline protection. piRNAs guide PIWI complexes to transposon loci, inducing heterochromatin formation or cleaving transposon transcripts via the “ping-pong” amplification cycle.​

(B) Incorrect Abbreviation

piRNA stands for PIWI-interacting RNA, not P-element interacting RNA. The term derives from interactions with PIWI subfamily Argonaute proteins, discovered in Drosophila and mammals.​

(C) Wrong Modification

piRNAs do not primarily modify the 2′-OH of ribose with a methyl group; this describes 2′-O-methylation on miRNAs or siRNAs by HEN1 enzymes. piRNA 3′ ends often feature 2′-O-methylation for stability, but silencing transposons defines their function.​

(D) Misclassified Length

piRNAs qualify as small non-coding RNAs (~24-31 nt), not long non-coding RNAs (>200 nt). Their brevity enables precise base-pairing with transposon targets.​