10.2 DNA provides evidence of evolution

what is a genome

the complete set of DNA in each cell of an organism

what is comparative genomics

• the genome sequences of different organisms are comapared

• compares human genome with other genomes to identify regions of similarity and differences.

what is “junk DNA”

• non coding sequences of bases in the DNA

• have no apparent function and serve no purpose

• comparisons provide similar results

• more closely related species have more junk sequences in common.

what is mitochondrial DNA

• DNA in the mitochondria (mtDNA)

• in the form of small circular molecules

• approximately 5-10 per mitochondrion

• 37 genes or approx 16500 base paris in human mtDNA

inheritance of mtDNA

• The amount of mutations between individuals mtDNA is proportional to the closeness of their relationship through their maternal ancestors.

• The more similar their mitochondrial DNA the more recent the common ancestor is on their maternal side. The more mutations between individuals mitochondrial DNA, the more distant the common ancestor is on their maternal side.

why do we use mtDNA as evidence for evolution?

• mtDNA is a lot smaller than nuclear DNA.

• There are many mitochondria in each cell so more mtDNA can be extracted.

• It is easier to track as mtDNA is only inherited from the mother.

• The same primers can be used between lots of different species when undergoing PCR.

• mtDNA has a higher rate of mutation than nuclear DNA