L2 Fun Topics Lecture 1 Evolution 2024-25 PDF

L2 Fundamental Topics in Biology Evolutionary Genetics Kevin O’Dell Thursday 3rd October 2024  Key Questions 1: How can a molecular genetic approach help us understand evolution and phylogeny? 2: What can DNA sequencing tell us about the ancestors of modern humans? 3: What can...

L2 Fundamental Topics in Biology Evolutionary Genetics Kevin O’Dell Thursday 3rd October 2024  Key Questions 1: How can a molecular genetic approach help us understand evolution and phylogeny? 2: What can DNA sequencing tell us about the ancestors of modern humans? 3: What can isolated populations tell us about the genetic basis of complex 1: Human Evolutionary Genetics We Look (a bit) Like Our Parents George Bush George W Bush US president US President 1989-1993 2001-2009  Comparative Anatomy Morphology suggests Humans and Apes are related: Large brains No tail Erect posture Flexibility of: hips ankle wrist thumb A Chimp GW Bush Changes to shoulder Fossil Evidence Note the number of branch points, extinctions and in some areas there is uncertainty in detail.  The Molecular Clock CAATTGATCC CTATTTAGCG DNA sequence from species A DNA sequence from species B CAATTGATCG CAATTGATCC common ancestor CAATTTATCG 10 million years later 20 million years later CTATTTATCG CTATTTAGCG DNA differences reflect evolutionary history Ape DNA Tree  We Look (a bit) Like our Parents 25%/100%/0% 6%/100%/0% 50%/0%/0%  Sequencing DNA is Easy! This device can sequence a genome is a few hours at a cost of £1000 Specific analyses can be completed with a few days 2: The Genetics of Our Ancestors Fossil and other evidence suggests Neanderthals and modern Humans co- existed in Europe as recently as 30,000 years ago. Are we the same or different species?  100,000 Years Ago Homo neanderthalensis Homo erectus Homo sapiens  25,000 Years Ago Homo sapiens  Neanderthal Evolution Noonan et al. (2006) Sequencing and analysis of Neanderthal genomic DNA. Science 314: 1113-1118  Human Migration >90% of human variation pre-dates humans leaving Africa  Human Variation There are about 300,000 chimps in the world. There are about 7 billion humans in the world. Chimps are more genetically variable than humans.  Sequencing Ancient DNA In 1991, Oetzi’s remains were found in a Glacier in the Italian alps. Analysis of his DNA suggests that: He died 5300 years ago He is ethnically Central European He may have been sterile To Quote a Top Scientist:- “At first it was thought that Oetzi had died from exposure to cold but wounds on his hands and an arrowhead lodged in his back suggest a Oetzi the Iceman more violent death”  New Species of Human? Slon et al. (2017) Neandertal and Denisovan DNA from Pleistocene sediments. Science 356: 605-608. 10,000 years of British Ancestry Leslie et al. (2015) Nature 519: 309-314. British Ancestry and Genetics Leslie et al. (2015) Nature 519:  Shared DNA by Descent Relationship Average % DNA Shared Range Identical Twin 100% 100% Parent/Child 50% 50% Full Sibling 50% 38% - 62% Grandparent/Grandchild 25% 17% - 34% Aunt Uncle / Niece Nephew 25% 17% - 34% Half Sibling 25% 17% - 34% First Cousin 12.5% 4% - 23% Second Cousin 3.1 % 2% - 6% Third Cousin 0.8% 0% - 2.2% Forth Cousin 0.2% 0% - 0.8% Fifth Cousin 0.05% 0% - 0.2% Finding close relatives is very accurate, but distant relatives less so. Ethnicity vs Nationality  3: The Founder Effect and Medicine Tristan du Cuhna is the most isolated human population on Earth  Tristan du Cuhna The current population of 264 is descended from 15 ancestors (8 male and 7 female) who arrived between 1816 and 1908, especially one Seven surnames survive: Glass (Scottish), Scottish family Green (Dutch), arriving Hagan (Irish), Lavarello (Italian), Repetto (Italian), in Rogers 1961 Volcanic Eruption Tristan da Cuhna is actually a very big volcano  Founder Effect Does such an isolated population derived from a small number of individuals show evidence of Ernst Mayr’s Founder Effect? According to Dr Noe Zamel from University of Toronto, inbreeding is so high that all islanders are cousins, and any two siblings are cousins by approximately 50 different routes. Genealogy Nine Y-chromosome haplotypes were found. Seven can be unambiguously associated with the seven surnames. These fall into two haplogroups: I: from south-western Europe (Italy) R: from north-western Europe (Dutch, English, Irish & Scottish). What of the other two haplogroups?  Genealogy Famil Males Haplogrou Haplotype y p 1 5/5 R-M207 15-12-25-10-14- 13 Explanation 2 3/3 R-M207 14-12-24-11-13- 13 Mutation 3 9/13 R-M207 14-12-23-11-13- 4/13 R-M207 13 New c1900? 14-12-23-10-13- 13 Non-paternity 4 8/9 R-M207 14-12-24-10-13- 1/9 R-???? 14 16-12-25-10-11- 13 5 16/19 R-M207 14-12-23-10-14- 3/19et al.I-M170 Soodyall 13 and gene: tracing the (2003) Genealogy 14-14-22-10-11- founding fathers of Tristan du Cuhna. Euro. J. Human Genetics  Founder Effect: Asthma Does such an isolated population derived from a small number of individuals show evidence of Ernst Mayr’s Founder Effect? According to Noe Zamel 23% of Islanders have asthma, with 57% showing some asthmatic symptoms. He suggests three  Evolutionary Medicine Islanders are likely to share the same pre-disposition genes. Islanders are essentially a single giant family