Get documents about "genetics
Shared by: cuiliqing
-
Stats
- views:
- 2
- posted:
- 9/6/2012
- language:
- Unknown
- pages:
- 52
Document Sample
BAHSHE 07-07-2003
Blood unites us: genetics and the
population history of the British Isles
David T. Croke
Royal College of Surgeons in Ireland
dtcroke@rcsi.ie
History
Anthropology Archaeology
Human origins & population
history
Genetics
Linguistics
What is the true history
of the populations of
these islands ?
Successive waves of
invasion
versus
Cultural exchange with
little or no movement of
people
Themes
Genetic variation as a tool to ‘probe’ population history
Anatomically Modern Humans - a brief history
Palaeolithic & Neolithic Europe - the ‘Atlantic fringe’
More recent events in the population of these islands
Population admixture in Ulster
Genetics and ‘race’
Genetic variation as a tool to ‘probe’
human population history
Harvard University Anthropological Survey of Ireland
Aran Islands ‘Keltic’
Waterford ‘Dinaric’
Mourant, 1954
Genetic ‘markers’ used in population studies
1. ‘Classical’ protein markers
2. Y-chromosome - paternally inherited
3. Mitochondrial DNA - maternally inherited
(mtDNA)
4. Recessive disease genes - biparentally inherited
Surveys within species reveal enormous genetic
variation between individuals
On average, about 0.2% of our DNA differs between
individual human beings
Human and Chimpanzees differ by ≤ 2%
The amount & rate of accumulation of variation can
be used to infer genetic relationship / ancestry
Tools
1. Availability of the human genome sequence and of
genetic ‘markers’
2. Laboratory methods
- Polymerase Chain Reaction [PCR]
- DNA samples from modern populations
- ‘Ancient DNA (aDNA)’
3. Population genetics theory
4. Mathematical & statistical tools
Anatomically Modern Humans
- a brief history
Hominid
Evolution
Anatomically
Modern Humans
[AMH] emerged
some 150 kYBP
Neanderthals and AMH did not interbreed
Ancient & modern mtDNA; MDS analysis
Krings et al., 1997
Caramelli et al., 2003
Neanderthals and AMH did not interbreed
Ancient & modern mtDNA; MDS analysis
Krings et al., 1997
Caramelli et al., 2003
Neanderthals and AMH did not interbreed
Ancient & modern mtDNA; MDS analysis
Krings et al., 1997
Caramelli et al., 2003
‘Out of Africa’
- a global palaeolithic population expansion
The ‘Neolithic Transition’ (Agricultural revolution)
Genetic traces of the neolithic expansion
Cavalli-Sforza et al., 1994
The ‘Atlantic fringe’ of Europe
North-western Europe is different
Y-chromosome haplogroup 1.15
Hill et al., 2000
Y chromosome haplogroup diversity (a)
Haplogroup 1.15 – the ‘Atlantic Modal Haplotype’
Wilson et al., 2001
Y chromosome haplogroup diversity (b)
A Y haplogroup spectrum shared with the Basques
- a palaeolithic ‘remnant’
Wilson et al., 2001
Y chromosome haplogroup diversity (c)
Little similarity to the Near East relatively little
Neolithic influence on the ‘Atlantic’ populations
Wilson et al., 2001
Neolithic contribution in Europe [Y data] Chikhi et al., 2002
6%
15% 67% 19%
21% 81%
23% 91%
41% 82%
14%
10% 0% 63% 100%
100%
Different male & female population histories [a]
Y DNA mt DNA
Y chromosome --> male-mediated gene-flow
mt-DNA --> female-mediated gene-flow
Wilson et al., 2001
Different male & female population histories [b]
Y DNA mt DNA
More female-mediated gene-flow (migration) between
continental Europe and the Atlantic populations
(excluding the Basques)
Wilson et al., 2001
What about the Celts ?
6,000 – 4,000 YBP
Ireland & Britain were
part of a Megalithic
culture spread across
Western Europe
Palaeolithic & Neolithic
admixture of peoples
The Celts were much later ! 1st millennium BC
Celticisation of
these islands ?
current model:
diffusion of elements
of celtic culture via
trading links
adoption of the celtic
‘cultural package’ by
local ruling elites
Cunliffe, 2001
Genetic evidence of more recent events
in the population of these islands ?
Y chromosome census
of the British Isles
Samples:
UK + Irl: 1,772
Norway: 201
Denmark }: 190
N. Germany}
Capelli et al., 2003
Reference populations
Capelli et al., 2003
Interpreting the data ?
Capelli et al., 2003
Overall, a degree of similarity AMH+1 > 33%
Capelli et al., 2003
Traces of Norwegian Viking admixture
Capelli et al., 2003
N. German/Danish influences in England & Scotland
Capelli et al., 2003
Recessive disease mutations
Phenylketonuria (PKU) and the population
history of Ulster
Phenylketonuria [PKU]
An inherited defect of amino-acid metabolism
Due to mutations in the Phenylalanine
Hydroxylase (PAH) gene [chromosome 12q]
29 different mutations have been identified in Ireland
Unidentified
Others
R408W
IVS12nt1
R243X
F299C
L348V I65T O’Neill et al., 1995
F39L
O’Donnell et al., 2002
Using PKU
mutations to
estimate Scottish
admixture in
Ulster
Ireland Scotland Analysis based on
frequency data for
13 PKU mutations
For Ulster as the
hybrid population
m = 0.46
Ulster
Admixture proportion estimated as:
m = (q2(rh-r2))/(q1r1-q2r2-rh(q1-q2))
O’Donnell et al., 2002
Does ‘race’ have a biological basis ?
Global human genetic diversity
H. sapiens (100%)
Within regional Between regional
populations populations
(90%) (10%)
Between local populations Between individuals within
Within regions local populations
(5%) (85%)
No biological basis for concepts of ‘race’ or ‘ethnicity’
After Relethford, 2003
“…we must disavow entirely any mystical view of
blood as a racial factor. Rather does a study of blood
groups show a heterogeneity in the proudest nations
and support the view that the races of the present day
are but temporary integrations in the constant process
of mutation, selection and mixing that marks the
history of every living species…”
‘The distribution of the human blood groups’
Arthur Mourant, Oxford, 1954
Suggested reading:
Steve Olson
‘Mapping human history: discovering the past through
our genes’
Bloomsbury Publishing Inc., 2002
Spencer Wells
‘The journey of man: a global genetic odyssey’
Penguin, 2002
John H. Relethford
‘Reflections of our past: how human history is revealed
in our genes’
Westview Press, 2003
