Download PowerPoint

1
Who thought this was a good idea?
http://www.youtube.com/watch?v=glii-kazad8
2
Corgis, dachshunds &
achondroplaysia
How’d that happen?
Semester review
❖
Flu viruses: how to reconstruct a tree-of-descent (phylogeny)
❖
Blue eyes: it’s the same set of eyes, over and over again!
❖
Milk drinking: genetically ‘solved’ by diff’t peoples in diff’t places
❖
Sickle cell anemia: same mutation; different origins
❖
That’s linkage
❖
So is your recent proposal
3
Achondroplaysia: bone
growth
http://www.healthhype.com/achondroplasia.html
4
Papers
1. “Genome-wide SNP and haplotype analyses reveal a rich
history underlying dog domestication” Nature 464: 898-902
2. “Genetic Structure of the Purebred Domestic Dog” Science
304: 1160-1164
3. “An Expressed Fgf4 Retrogene is Associated with BreedDefining Chondrodysplasia in Domestic Dogs” Science 325:
995-998
4. “The Dog Genome: Sequence, Evolution, and Haplotype
Structure” The Dog and Its Genome, Cold Spring Harbor Press
2006
5
Dog breeds are ‘real’
Each label marks five unrelated dogs of a breed
Color indicates a pattern of sequences
Note how each breed is different than others and individuals in it are
same
6
FYI: ‘chunking’ dogs
7
Dachshund, corgi, basset
hound
Form hypotheses about
short-legged dogs
What predictions would you
make about these breeds vs.
other dog breeds?
8
Needles & Haystacks
9
All short-legged dogs have a specific form of
the DNA chunk in a particular region of Chromo 18
All other dogs lack that version of the chunk
Ref. 3
10
TBA
“An insert of about 5 kb starting at position
23,431,136 (fig. S1) was found by tiling polymerase chain reaction (PCR) amplicons across
the homozygous region. This insert was present in
all dogs from the original eight breeds and 11 of 12
additional breeds that fit at least two of the three
chondrodysplastic criteria (175 dogs from 19
breeds)”
Ref. 3
Basset Hound
11
Where
are ours?
Dachshund
Corgis
Ref. 2
Flies in ointments
12
Stop! Think
❖
How did dogs ‘happen’?
❖
How did dog breeds ‘happen’?
13
Evolution, genes, individuals
❖
Look around. There’s diversity in our little population here
❖
How many ‘184 breeds’ could we create?
❖
What would happen to the diversity in those subpopulations?
❖
What if we selected for a PTC-tasting pool & a dimpled pool
❖
What would be the eye color of each pool?
Population thinking
❖
A species is a bunch of organisms that can interbreed
❖
At any given time, then, it is not a genotype, but a collection
of alleles
❖
❖
Hence the term ‘gene pool’
To go back to an earlier lecture, evolution is defined simply as
a change in the frequency of alleles in the gene pool
14
15
Looking back
“Through… simulations, the experimental results were
recapitulated using a dual-bottleneck population model for dog
breeds, assuming commonly accepted mammalian mutation
and recombination rates. With an initial domestication
bottleneck... approximately 27,000 years ago (9000
generations) with an effective population size of 13,000, and a
subsequent, breed-creation bottleneck, the simulated data
successfully mimicked the [findings].
Modeling the second breed-creation bottleneck for individual
dog breeds... breed creation about 50 generations ago (100–
200 years) with a moderate bottleneck... recapitulates the
experimental data and is consistent with historical records.”
Ref. 4
River out of Eden*
*Title of Richard Dawkins book
16