Question

Describe what is meant by the terms ‘pan genome’ and ‘core genome.’ What sorts of genes do you expect to be present in the core genome? What sorts of genes are found in the pan genome but outside the core genome? What processes of genetic exchange give rise to the great diversity of genome sequences in the various strains of a given species?

Answer 1

In the fields of molecular biology and genetics, a pan-genome (or supragenome) is the entire set of genes for all strains within a clade.The pan-genome includes: the core genome containing genes present in all strains within the clade, the accessory genome containing 'dispensable' genes present in a subset of the strains, and strain-specific genes. The study of the pan-genome is called pangenomics.
The pangenome is the entire gene set of all strains of a species. It includes genes present in all strains (core genome) and genes present only in some strains of a species (variable or accessory genome). The core genomerepresents the genes present in all strains of a species.

The core genome represents the genes present in all strains of a species. It typically includes housekeeping genes for cell envelope or regulatory functions. The variable or accessory genome (also: flexible, dispensable genome) refers to genes not present in all strains of a species.

Repeated rounds of this process of duplication and divergence, over many millions of years, have enabled one gene to give rise to a whole family.

There are various mechanisms that have contributed to genome evolution and these include gene and genome duplications, polyploidy, mutation rates, transposable elements, pseudogenes, exon shuffling and genomic reduction and gene loss.