Genetic studies of early human populations Flashcards Preview

human genetics and evolution > Genetic studies of early human populations > Flashcards

Flashcards in Genetic studies of early human populations Deck (34):
1

when was H. erectus in africa vs when in Eu/asia

1.9mya
1.8mya

2

when was H. neaderthalensis in Eu

200-30kya

3

when did Homo sapiens in Afr

195kya

4

when did homo sapiens in eu

65kya

5

how do genetic studies study human pre history

look at modern pops to make sense of ancient

6

how is genetic diversity found in modern pops and how has this changed

dna seq
used to be only mt DNA and y chr dna
now whole genome

7

what are some methods for infering deviersity evolution

phylogenetics - patterns of div as tree/network
dating - method assign dates to key positions in an ev scheme
phylogeographic - interpret diversity of pop migr

8

what are the problems with the methods for infering the diversity evolutio

do they produce anything real or just a narrative
lots of diff way data can be interpreted
lots of data - lot of computer power required

9

why is mtdna good to study

most rapidly ev part of genome
easy seq

10

what is the d loop

the most variable part of mt dna
lot of ev here as no sel pressure as there are no genes on this bit of dna as it is the origin of replication
most early studies used dloop amplified by pcr

11

what has next gen seq meant for mt dna studies

now look at whole genome of mt dna not just d loop
put into haplogroups

12

what arehaplogroups

275
diff groups assoc with diff parts of the world
not distinct seq but related seq
have subsitututions which categorise

13

what are haplogroups made up of

haplotypes - mixture of seq
share subsitiutions of haplogroup
but have own distinct substitutions that define (these allow the ev relationships between haplotypes to be worked out)

14

if haplotypes are rare this shows

the result of recent mut

15

how are networks built

compare subsitutions
want maximum parsimony
trees are diff ypothesis that make sense of the data
networks - lots of diff trees

16

what is a principal node

many have this haplogroup
the defining subsitutions

17

what is an empty node

unknown haplotype in modern human pop
or existed in past and now extinctqqqq

18

what shape do netowrks form in expanding pops

starburst

19

in a network what shown by peripheral node

have own unique substitutions

20

what does coalescent analysis reveal

date the origin of the haplogroup
expresses date in generations

21

what is founder analysis

an extension of the coalescent analysis
use diversities of haplogroups to estimate time of pop split
eg study bottleneck - group that leaves bottleneck decr gen div-but overtime incr in div and then compare w source pop
allows effective pop size of bottleneck to be calculated

22

what is the problem with past study on mtdna and y chr

narratives
small bit of genome
animal studies no longer use

23

why is whole genome seq preferred over mtdna / y

more sophisticated as more snp/ recomb between pat v mat dna

24

what is the issue with whole genome seq

dont yet knwo how to analyse rigourously

25

what thought to occur between 130-190kya to homo sapiens

bottleneck

26

what genetic ev is there for homo sapien bottleneck

low gen div - about 25% of other hominids#
mito eve dated 190kya - suggest pop expand then
coalescence analysis of 50 nuc genes suggested a effective pop size of 2000 at 130kya

27

what archaeological evidence is there for a bottle neck in homo sapiens

decr in dwellings around the time predicted to occur

28

what are the three hypothesis for the affect of climate change on human pops

- founder hypothesis , pop contracts/argue that only one pop of h.sap survived and we all descended from this one pop
- fragmentation hypo - human pops in afr divided into sep grps w no gene flow between . aridity severe caused
- no bottleneck

29

why studies of pot bottleneck use modern afr seq

aas carry mat/pat lineages of some of the deepest clades in mod humans

30

what was the main finding of Sjodin et al., 2012

model doesnt support bottleneck
found that the option of the no bottleneck most liekly model for all afr pops looked at (at least 79%)
therefore the bottleneck is illusory

31

why is the conc of bottleneck being illusory paper importnat

reconsider the refugia pleistocene hypo
shows mtLCA not enough

32

what did the paper by yi & dublin find ev for based on 2 yoruba genomes

pop expansion during 190-130kya

33

what explains the low diversity

selecive sweeps throughout genome

34

what are selective sweeps

env pressure puts sel on many genes
aar these genes less diverse as adpative
allele therfore selected and incr in pop
recomb decr lenth of segments subject to sel
aar mut and dna on either side becomes fixed and dating thus inaccurate as this not been taken into aacocutn