Question

How did a genome evolve over time? Describe some of the common mechanisms by which genome evolution occurs (consider how individual species evolve new traits and how speciation itself occurs over time) What mechanisms have had the greatest impact?

Answer 1

It can be understood by Hardy Weinberg Principle, according to which allele frequencies remain constant. Any change in them leads to evolution.

Factors that affect the principle are:- gene migration or gene flow, genetic drift, mutation, genetic recombination and natural selection.

Gene migration - When a population moves to a new place and new population is produced from them, frequencies in new as well as old population changes leading to evolution. New genes are added in new population and removed from old. If this happens multiple times, it is called gene flow.

Genetic drift - If the above mechanism happens by chance, it is called genetic drift.

Mutations - These are constantly happening in ones genome. It can lead to either negative effect, positive effect or no effect at all. But it still results in changes to genome.

Genetic recombination

Natural selection - leads to selection of traits favorable to survival of species.

Other factors include - transposable elements, pseudogenes, exon shuffling.

Most common of these all are genetic recombination, mutations, and natural selection.

When the change in allelic frequency is so different, that it leads to generation of entirely different population or species, selected by natural selection process. It is called speciation.

Large sized mutations and genetic recombinations have greatest impact over evolution.