Week 7: Molecular Evolution

DNA-DNA hybridisation

combine strands of DNA at high temperatures

• the higher the temperature the stronger the hydrogen bonding and the closer related the DNA strands are

mitochondrial DNA

• mutates faster than nuclear DNA

• no repair enzymes

• slowly degrades after death

D-loop

hypervariable segment in mtDNA

RFLPs

restriction fragment length polymorphisms, the length can be used to group people by haplotypes into haplogroups

HVR1 and HVR2

control region includes 2 hyper variable regions that mutate faster and by sequencing them you ca define a person’s mitochondrial haplotype

mitochondrial “Eve”

root of mtDNA in Africa 200,000 years ago

• there was not a single Eve and African populations are more diverse than non-African

Y chromosome

mtDNA is tracked to be much younger of an African origin, no recombination

difference between human and ape genomes

98.8% similar, differ in the dosage / regulation of identical genes

FOXP2

language gene

human accelerated regions (HARs)

region in the genome where the human lineage shows the highest number of changes

HAR1

most dramatically accelerated HAR, active in developing humans and expressed in testes

VLDLR gene

(very low density lipoprotein receptor) Turkish family who walk on all fours have a missense mutation in this gene causing disorder with cerebellar dysfunction and gait

other gene candidates for bipedality

genes of HOX family and the loss of GDF6 (opposable toe) growth differentiation factor 6

Recent African Origin Model

modern humans arose in Africa 100,000 years ago and spread throughout the world completely replacing other archaic human populations with no interbreeding

(African) Hybridisation and Replacement Model

humans spread from Africa and interbred with the other populations eventually replacing them

Assimilation Model

arose in Africa and migrated out, interbred extensively leading to genetic mixing rather than complete replacement

Multiregional Evolution Model

denies African origin and emphasises genetic continuity and gene flow between continents