05 Molecular Evolution

Karyotype

(complete set of chromosomes)
of the human genome

Genome structures within organisms

eukar have linear, bacteria has circular also archaea as we

Exons

protein coding sequences

introns

none coding sequences

homologous genes

that share a common ancestral origin but may have different functions in different species. They can result from evolution through gene duplication or speciation.

Orthologous genes:

• The SAME gene in different species (or individuals) like hemoglobin genes in humans and mice

Paralogous genes

Genes that are COPIES of each other in the same species or in
different species
• Arise due to duplication events, like globin genes: the human forms hemoglobin and myoglobin

Central dogma

DNA to RNA to protein

Synonymous substitutions

• Due to redundant genetic code
• Does not change the amino acid / protein sequence
• Usually considered neutral (not under selection)

Non-synonymous substitutions
• Changes the amino acid

Non-coding substitutions

• Usually, no effect on protein so considered neutral
• May effect expression level (adaptive or deleterious)

Non-synonymous substitutions

• Changes the amino acid
• May be adaptive, deleterious, or neutral

what is Ka and Ks

Ka = Non-synonymous substitutions per site
Ks = Synonymous substitutions per site

• Ka/Ks – measures the rate of protein evolution relative
to the neutral rate

ka/ks>1

positive adaptive selection, more amino acid changes

ka/ks<1

purifiying selection, less amino acid changes

ka/ks=1

neutral evolution and amino acid is occurring same time as neutral changes