The Science Of Dogs: Genetics

18 Pages·2010·3.06 MB·English

The Science of Dogs:
Genetics
1) Genetics of Dogs
2) How Dog Genetics Can
Help Humans
Pan-Pan Jiang
1) Genetics of Dogs -
Meet Canis
Canis lupus
Canis lupus familiaris
Canis aureus,
Canis mesomelas,
Canis latrans
Canis simensis
Artificial selection creates breeds
Dog breeds are homogeneous
Dogs Humans
Chihuahua Great Dane Africans Asians
What is Genetics?
Genetics – study of genes and heredity
A G T C
nucleotides
DNA
Chromosomes
Humans: 3.0 billion nucleotides Humans: 46
Dogs: 2.4 billion nucleotides Dogs: 78
Different breeds, different species?
ref: ATCGTCAATG
1: ATGGTCAATG 1/10 differences - 10%
2: ATGGTCACTG 2/10 differences - 20% More different
Canis lupus familiaris Canis lupus familiaris Canis lupus familiaris
vs vs
vs Canis lupus
vs
other canids
5% different
8% different 5% different
DNA gives us 4 major dog groups
A) Asian breeds, Asian-
descent hounds, spitz-type B) Broad frames and large head
C) Working breeds
D) Hunting breeds
Use number of repetitions to
Microsatellites - repetitive regions in our genome
assign dogs to breeds with 99%
Individual 1 - CACACACACA - (CA)5
accuracy, assign breeds to
Individual 2 - CACACACACACACACA - (CA)8
major groups
R E V I EW S
Rarest 86 breeds 5% species populating both the Old and New World five
Labrador retriever 16% centuries ago, when Europeans found the Americas5.
So, dogs either came to the Americas with humans
from the Old World or they were domesticated inde-
Golden retriever 6% pendently in the Old and the New World. The pheno-
Bichon frise 1.0% type variation in dogs led Charles Darwin to argue that
Basset hound 1.0%
Pembroke Welsh corgi 1.1% different breeds had been independently domesticated
Siberian husky 1.2% Beagle 5% from wild CANID species on different continents, per-
Doberman pinscher 1.3%
German shorthaired
M paolitnetseer 1.43% sGheerpmhaenr d dog 5% hspaepcsi edse6.scMenitdoicnhgo fnrdormia lw soeqlfu, ceonycoe tdea atna,dh soewvervaelr ,jashckoawl
Miniature pinscher 1.4%
SheBtlaonsdto snh teeerrpiedro g1 . 61%.7% Dachshund 4% mthaetn dt,oVgisl ad eestc aeln.7da snoalelylys efrdo 2m6 1w bolpv eosf. Imni ato kcehyo enxdpreirai-l
Buldog 1.8% Yorkshire terrier 4% sequence from dogs, wolves and other wild canids, and
Rottweiler 2.0%
Cocker spaniel 2.1% Boxer 3.7% showed that dog and wolf mitochondrial HAPLOTYPES
Pomeranian 2.3% Poodle 3.5% were similar. Indeed, the most dissimilar haplotypes
Pug dog 2.3% Shih tzu 2.9%
Miniature schnauzer 2.4% Chihuahua 2.7% between the two species differed by no more than 12
substitutions. By contrast, the minimum number of
Figure 1 | Proportion of purebred dog registrations by the American Kennel Club (AKC). differences between dog and other wild canid haplo-
A total of 916,000 purebred dogs were newly registered in 2003 in the United States by the AKC,
types was 20 substitutions7. Subsequent phylogenetic
which is the largest purebred dog registry in the United States and that recognizes over 150
Amdistincet brreedis.c Thea monst po puKlar 2e0 brneedsn acceounlt fo r 7C0%l ofu all rebgistr atRions.e Thec rareost 8g6 niaznaleysisd of m iGtochronodriual happlostypes identified four
breeds cumulatively account for just 5% of registrations. Many rare breeds newly register fewer canid CLADES, including one containing 19 of the 26
than 100 animals per year. dog haplotypes, but no wolf haplotypes. The existence
of a dog-specific clade with high haplotype diversity
DNAsu-pipnofrotsr am reladti vdeloy gan gcirenotu tpimse frame for the
domestication of dogs, perhaps >100,000 years before
misc A) Athsei parense nbt7r.eeds, Asian hounds
B) BroMaitodc hfornadmriale sesquence data have also been used
C
to refute the New World domestication hypothesis.
C) Working breeds
Mitochondrial DNA was sequenced from archaeologi-
D) Hcaul dnogt ispnegci mbernes ceodllescted throughout the Americas
and dating before the arrival of Europeans. The haplo-
types fit with those from modern breeds, which are
misc D
Non- Herding known to have come from Old World domestication.
sporting They also included a large number of haplotypes
Toy Sporting assigned to one of the dog-specific clades5. Therefore,
the haplotypes do not provide any evidence for an
independent domestication in the New World.
Terrier Hound
Savolainen and colleagues refined this picture by
Working examining mitochondrial haplotypes from 654 dogs
representing main populations around the world8.
D
They report a similar phylogeny in every geographic
region, suggesting a single domestication event in one
gAeo/graDphic region. The greatest haplotype diversity
occurs in East Asian dog populations, consistent with
the notion that the key domestication event occurred
in Asia8.
Beyond the time and place of dog domestication,
there is interest in how domestication occurred. In
Figure 2 | Grouping of dog breeds by the American Kennel Club (AKC). The American what ways do all domestic dogs differ from wolves?
Kennel Club categorizes dog breeds into seven Bgroups based on historical development, This has been addressed recently by Hare and col-
morphology and behaviour. Representative breeds from each of the AKC groupings are shown.
leagues, who studied how dogs and wolves differ in
The German shorthaired pointer is a member of the sporting group, which includes breeds used
their ability to relate to humans9. They devised a study
for hunting and retrieval of wild animals. The Pharaoh hound represents the hound group, whose
members hunt independently using sight and speed (greyhound) or in packs (beagle) or by in which dogs were challenged to find a hidden food
scent (bloodhound). The mastiff is a member of the working group, a set of breeds used for reward, aided by a human who stared and pointed at
guarding, fighting and drafting. Many of these breeds are heavily muscled, sharing the the treat’s hiding place. Adult dogs and puppies, even
‘molosser’ morphology. The Welsh terrier depicts the terrier group, a set of breeds used those raised with little human interaction, did signi-
primarily for vermin extermination. The Maltese represents the toy group, which features breeds
ficantly better than wolves. Dogs have therefore
of small body size. Many share morphology with larger breeds in other groups (for example, the
acquired a social-cognitive capability to ‘read’ humans,
I
ntaolnia-ns pgorertyinhgo ugnrodu ips ,a a t omyi swciethlla tnheo suigsh ctlhuosutenrd o mf borrepehdoslo wgiyth). lTithtle schaorwed c hmoowrp ish oal omgeym orb heirs otof rtyh.e which is lacking in wolves9. Identifying the genes
The cardigan Welsh corgi is a herding dog, a group defined functionally as breeds used to herd that regulate such evolutionary events will be both
and guard animals. challenging and exciting.
NATURE REVIEWS | GENETICS VOLUME 5 | DECEMBER 2004 | 901
© 2004 Nature Publishing Group
Trait mapping
pos 3 8
Pos 3 Wrinkly Smooth
ref: ATCGTCAATG
C 101 105
1: ATGGTCAATG
G 105 95
2: ATGGTCACTG
Pos 8 Wrinkly Smooth
A 6 98
C 93 7
Traits mapped:
Wrinkliness
Coat color, curl, length
Size
2) Dog genetics and humans
Dog genome sequenced in 2005
"The incredible physical and behavioral
diversity of dogs — from Chihuahuas to Great
Danes — is encoded in their genomes. It can
uniquely help us understand embryonic
development, neurobiology, human disease
and the basis of evolution."
- Eric Lander, 2005