Question

Retroviruses integrate into DNA so viral DNA starts off as an mRNA sequence. If the original sequence is 5' GGCAACU 3', the transcribed mRNA used to make proteins will be.

A) 5' GGCAACU 3'
B) 5' AGUUCCG 3'
C) 3' CCGUUGA 5'
D) 3' UUGCCA 5'

Answer 1

The transcribed mRNA sequence from a retrovirus original RNA sequence 5' GGCAACU 3' will be the same, making option A) 5' GGCAACU 3' the correct answer.

Step-by-step explanation:

Retroviruses are unique in that they use their RNA genome to synthesize a DNA version through an enzyme called reverse transcriptase. This DNA is then integrated into the host's genome. When the viral DNA is transcribed, the mRNA sequence produced will be complementary to the original viral RNA sequence but will be in the same 5' to 3' direction as the original RNA because mRNA is synthesized in this direction. Given the original sequence 5' GGCAACU 3', the transcribed mRNA will be 5' GGCAACU 3'.

To synthesize a DNA strand from the RNA sequence, the reverse transcriptase would generate a complementary DNA using the RNA as a template. The DNA sequence would be 3' CCGTTGA 5', which would then serve as a template for transcription. The RNA polymerase would create an mRNA with the same sequence as the original virus RNA, leading to option A) 5' GGCAACU 3' being the correct answer.