• You can classify the evolutionary relationships between species by examining their features
• Much of the Tree of Life was developed by observing phenotypes and then inferring relationships based on species that have the most similar phenotypes

• You might conclude that eye development occurred through different paths for humans and flies since the morphology is so different
• Mutations in the Pax-6 gene cause small eye in mice, knockouts have no eyes
• The Pax-6 homolog in flies (eyeless-ey) has
94% amino acid identity with small eye

• You can knockout the Pax-6 gene in the fly and you get a fly with no eyes.
• You can put the mouse Pax-6 gene into a fly with the fly version of Pax-6 knocked out and you get eyes again.
• You can put mouse Pax-6 on other regions of the fly body and get extra eyes

• Many detailed phylogenetic relationships can only be inferred using dna
• The two eye genes descend from a common ancestor to both flies and humans
• The gene wasn’t changed because it is important to survival

• Mutations that confer an advantage will tend to dominate in a population
• When separated, populations will eventually lose the ability to mate and their population will differentiate from other populations
• You can determine the evolutionary distance by looking at the number of mutations in a common gene

• 18s produces the small ribosome that is used by all eukaryotic organisms
• We can compare it across all of life
• Barcode

• Mitochondrial DNA comes only from the mother
(sperm don’t have mitochondria)
• Y chromosome comes only from the father and doesn’t recombine with other chromosomes
• Mitochondrial Eve is the common ancestor (or group of ancestors) that originated mitochondrial dna
• Mutations can occur that don’t impact the fitness, but are single nucleotide polymorphisms

• You can determine the age of a species by noting how much variation there is in a species
• Two chimpanzees are 10-15 times more different than each other than 2 humans
• Humans are a recent species that hasn’t had the chance to accumulate much diversity
• Small populations tend to lose mutations
(genetic drift)

• Fletcher Christian shipwrecked on Pitcairn island
• Almost everyone now has the last name of
Christian
• 7 types of mitochondrial DNA in Western Europe, so there were 7 women that were the ancestors of all western European women
• By molecular clock you can estimate that about
150,000 years ago there was a woman that all of our mitochondria came from

• 70% of finish men have a SNP on the Y chromosome that is unheard of in other
European countries
• 2 million men in Finland all descend from a common male ancestor that didn’t interbreed much with other countries
• Modern european humans descend from a group of about 20 people that migrated recently from africa

• Y chromosome is largely european
• Mitochondria is largely native
• You can explain a lot of human history by looking at DNA

• Genetics show what the name does not intuitively show

40
Discovering Previously-Unknown
Relationships
36 Generations
30
20
10
A Sorenson B C D E F Sorensen G

• Two individuals theoretically share all their ancestors at a very recent point in time
Common
Ancestors
Unique
Ancestors
Unique
Ancestors
Individual 1 Individual 2

• Cohen in Hebrew means high priest, and Cohens are always the son of a Cohen (no adoption)
• Cohens are supposed to be descendents from Aaron
• Cohens are 4% of people in Israel
• Select 100 Sefardi Cohen's from Spain, north africa, Iraq etc
• Select 100 Ashkenazi Cohen’s from Europe
• 70% of Cohens have the same Y chromosome polymorphisms, where only 15% of the general population does
• Over 3000 years, Cohen’s have almost all descended from one ancestor

• Tribe in Africa that are rumored to have the ruling class descended from Jews
• Almost all of the ruling caste have the Cohen polymorphisms
• None of the other caste members have the mutation

• Because humans are such a young species with a small number of SNPs, we can associate the SNPs with characteristics