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http://www.youtube.com/watch?v=ZSBq8geuJk0
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Summary from round I
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Dogs.
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Short-legged dogs have same, VERY DISTINCT (= highly
unlikely) causal mutation
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Predict: common origin!
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Test: relatedness
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Finding: Nope. Short-legged dogs often more related to
many long-legged breeds than other short-legged
Now what?
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River out of Eden*
Domestication
Breed creation
*Title of Richard Dawkins book
Ref. 4
In other pictures...
Wolf gene pool: all the alleles amongst wolves
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Dogs
Wolf gene pool
Dog gene pool
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Breed 1
Breed 2
Breed 3
Dog gene pool
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Recreating history
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The structure and specific sequence of the insertion & its
target let us ‘look at’ this event from tens of thousands of
years ago
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We will work backwards, then forwards to look backwards!
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Meteor strike?
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The DNA change is not a single nucleotide (base) change
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It’s an insertion of ~5000 bases... of a growth-related gene!
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How can this happen? Where did it come from?
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Hint: some viruses live this way!
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1
2
Different than flu:
fuses, not engulfed
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4
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http://www.rkm.com.au/VIRUS/HIV/HIV-images/VIRUS-HIV-life-cycle.jpg
I need to
become a
gene!
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What’s in a word?
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Transcribe: re-write (in bio, make an RNA copy of DNA)
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reverse transcribe: make a DNA copy of RNA
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reverse transcriptase: one that does that
Like… and unlike!
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The inserted DNA looks like another dog gene
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and a human one--that controls growth!!!
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This makes sense--another tool of hypothesis testing
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But its got pieces missing compared to the original?!?
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How can this happen?
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Hint: eukaryotes (which are what) make RNA this way
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The splicing story
content
‘commercials’
http://purpleopurple.com/inventions-and-inventors/gene-exons-and-introns.jpg
Sidenote: yeah--not magic.
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http://genesdev.cshlp.org/content/17/4/419/F1.large.jpg
Picking out the pieces
‘Landing site’ of
retrogene DNA
(GTTA)
Source of the
retrogene
read as “came
from”
Note ACA = ACA
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Where’d that come from?
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Summary
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Short-legged dogs have a common mutation
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Not from immediate ancestry
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Likely lost from other lineages rather than new to these
Insertion is a ‘retro-gene’ for a growth factor
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the same growth factor gene that is altered in a
common form of human dwarfism
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How I
drew it up
(entire map posted
with lecture)
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Reserve/unused
material
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Losing diversity
Random
Each column is a
subset
length of DNA.
Note no correlation top selected
& bottom
Few chromosomes
Often homozygous
Little opportunity
for recombination
Giant stretches
not recombined
Ref. 4
Bad words
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[Linkage Disequilibrium] describes the association
between pairs of loci in the genome. For example, if
individuals with allele A1 at locus A are significantly
more likely to have allele B1 at locus B, the two loci
are in linkage disequilibrium.
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Or: Are genes as free to wander as we’d expect? Or
are they acting like they are ‘tied together’ more than
predicted by physical distance
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