Question

In eukaryotic cells, we sometimes find reverse transcriptase activity, even though the cells are not infected with a retrovirus. This activity can be attributed to?

1) the presence of transposons integrating into polymerase genes
2) the presence of viroids
3) the presence of retrotransposons
4) infection with small bacteria known as mycoplasmas
5) a novel prion infection

Answer 1

Reverse transcriptase activity in eukaryotic cells without retrovirus infection is most likely due to the presence of retrotransposons. These genetic elements can move within the genome via reverse transcription, similar to retroviruses like HIV, but they do not form infectious particles. The correct option is 3) the presence of retrotransposons

Step-by-step explanation:

In eukaryotic cells, reverse transcriptase activity can sometimes be found even in the absence of a retrovirus infection. This activity can be attributed to the presence of retrotransposons, which are genetic elements that can transpose themselves to new positions within the genome via an RNA intermediate that is reverse transcribed into DNA. Retrotransposons bear a close resemblance to retroviruses but do not form infectious particles.

Unlike retroviruses, which require infection to replicate, endogenous retroviruses (ERVs) are remnants of ancient viral infections embedded in the host genome and can act as retrotransposons. These ERVs can produce reverse transcriptase even though they are not part of an active virus. In this case, the retrotransposons perform a similar function to active retroviruses by reverse transcribing their RNA back into DNA, which then gets integrated into the cell's genome.

Thus, the correct reason for finding reverse transcriptase activity in uninfected eukaryotic cells is option 3, the presence of retrotransposons. The correct option is 3) the presence of retrotransposons