Question

Endogenous retroviruses (ERV) make up 5~8% of human genome. These ERV are ancient retroviruses which infected germ cells and therefore became parts of our genomes. However, unless the ERV can increase the survival chance to its host, it wouldn’t be able to expand its frequency in our genetic pool. So there must be some mechanisms that expand the copy number of ERV. The infection of germ cells can happen more than once. Alternatively, ERV can reactivate at some point of the development of the host and make new copies in the genome. Considering that the sites of integration of retroviruses are highly random, even the same ERV can appear in different loci or different chromosomes. Have large scale genome sequencing revealed a heterogenic map of ERV?

Answer 1

ERVs are remnants of ancient viral infections that are part of our genetic makeup. Large scale genome sequencing confirms the heterogeneity of ERV locations across individuals, behaving similarly to LTR retrotransposons. They influence the copy number of ERVs within the genome without forming infectious particles.

Step-by-step explanation:

Endogenous retroviruses (ERVs) are remnants of ancient viral infections that occurred in germ cells, and these genetic elements have been passed down through generations, comprising approximately 5-8% of the human genome. The integration sites of ERVs within the genome are highly random, which has led to a heterogeneous map of ERV locations across individuals. Large scale genome sequencing indeed confirms this heterogeneity, showing that the same ERV can be found in different loci or chromosomes among individuals.

This divergence arises due to mutations that can inactivate genes needed for infection, rendering some ERVs similar to LTR retrotransposons. Such ERVs can still be transcribed and their cDNAs can re-enter the nucleus to integrate into new genomic locations, thereby expanding the copy number of ERVs without producing infectious viral particles. However, the impact of ERVs on host survival and their role in evolutionary processes remains a subject of ongoing research.