What piece of the RNA HIV genome is used as a primer during the synthesis of double-stranded DNA from HIV RNA?
A) tRNA
B) U3
C) gag
D) PPT

Question

Quizplus · Accepted Answer

During the synthesis of double-stranded DNA from HIV RNA, a primer called the polypurine tract (PPT) is used to initiate reverse transcription. The PPT is located at the 3' end of the HIV genome and consists of a stretch of purine nucleotides (either adenine or guanine) followed by a few pyrimidine nucleotides (either cytosine or uracil). This sequence serves as a binding site for the reverse transcriptase enzyme that allows the copying of the RNA into DNA. Therefore, choice D, PPT, is the correct answer. tRNA is not used as a primer during HIV reverse transcription, although it does serve as a template for the synthesis of some viral proteins. U3 is a promoter region located at the 5' end of the HIV RNA genome, but it is not used as a primer during reverse transcription. The gag gene encodes for viral structural proteins, but it is not used as a primer during reverse transcription.

What Piece of the RNA HIV Genome Is Used as a Primer