Lecture 17 Flashcards
dn is not the number of changes at non-synonymous sites…
it is the number of changes at non-syn. divided by the number of non-syn. sites.
Evolution cant just be becuase of natural selection since___.SImple ____would seem to be the ideal first step towards the goal
from bacterium only numerous forms of bacteria would have emerged.
doubling of chromosome groups to produce tetrapoily
goal of increasing the chromosome materials
Explain photo 14. Arabidopsis plot
All species have a large bar to the left why?
Why is their a hump?
genes are constantly producing new gens creating back up genes and blast doesn’t recognize them
Lots with very few substitutions with silent sites.
The hump represents a set of genes, that experienced gene lost at the same rate as the genes around them but here the loss started after the rare and very large gene duplication event(a WGD)
What were the two conclusions made to explain the drop in bars in photo 14?
conclusion 1-most new genes are quickly lost
conclusion 2-the rate of gene duplication id of the same order of magnitude as the rate of substitution per nucleotide site
What does the data on photo 15 show?
ds is on the x-axis and dn on y-axis
dn/ds is the dotted line=1.0
young pairs on the left
This data show that dn/ds is close to 1.0 for recent duplicates and later is less. Thus the period that change is common as silent sites is short.
unfilled dots=dn/ds=1
filled dots=dn/ds<1
Photo 15 found that once ds reaches 1.0 it becomes a poor estimate of divergence time
why? what paper was viewed
Shows that dn/ds close to 1.0 for recent duplicates and later dn/ds less the 1.0
Zebra fish box Cluster and Vertebrate Genome Evolution
Comparative genomics provides evidence for an ancient genome duplication event in fish
Visual opsins are a nice example of?
duplicated genes that survived and diverges in a way that turned out to be beneficial. In this case, the benefit of duplication and divergence was for better colour vision
