Question

how is genome size affected by the population size and how can multiple genes get packed into a single region of a viral genome?

Answer 1

Genome size affected by the population size:

Small population size leads to the large genome due to the mutations that lead to the duplication of these genes. The duplication could possess positive, negative, or neutral (rarely) effect for the organism

how can multiple genes get packed into a single region of a viral genome?

Mostly the virus has overlapping genes, which means one sequence can encodes for more than a protein.

Like if there is a given sequence AATTCGCGA,

• if we read it starting with A it will be AAT TCG CGA, this will code for example PROTEIN-1
• but, if we change the reading frame and start with Second A  ATT CGC GA this will code for PROTEIN-2

This is how by keeping a single sequence but changing the reading frame a virus can accommodate multiple genes in small regions of the genome.