Lecture 5 Flashcards Preview

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Flashcards in Lecture 5 Deck (11)
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1
Q

Conspicuous phenotypic divergence between humans and chimpanzees:
(8)

A
  • Hairless
  • Loss of muscle strength
  • Delayed post-natal development
  • Different suit of disease susceptibilities
  • Big brain
  • Language
  • Complex vocal organs
  • Funny noses
2
Q

dN/dS comparisons between humans and chimps reveal:

3

A
  • Individual genes
  • Genes grouped into biological processes
  • Genes grouped by the tissue they are most abundant in
3
Q

Biological processes affected by positive selection between human and chimps include:
(3)

A
  • Immunity and defence
  • Chemosensory and sensory perception
  • Spermatogenesis and motility
4
Q

What tissue is adapting at the fastest rate between humans and chimps?

A
  • The genes expressed in the testis
5
Q

Comparing humans and chimps with an outgroup enables us to determine which lineage the changes happened down. This prooved
(3)

A
  • 400/16529 genes displayed positive selection
  • 10 genes are evolving adaptively in humans
  • dN/dS is lower suggesting that there is more purifying selection occurring
6
Q

An immune protein that is a Hep C viral receptor, appears to be adapting really quickly. Why?
(3)

A
  • Amino acid change is favoured as it gives you resistance to the Hep C virus.
  • This is an evolutionary arms race between the viral receptor and the virus
  • Most changes are localised to the virus binding region
7
Q

Adh gene in D.melanogaster

A

Balancing selection acts on the fast/slow polymorphism

8
Q

The MacDonald Kreitman test under the neutral model:

3

A
  • The patters of nucleotide variation WITHIN species should match the patterns of nucleotide variation BETWEEN species
  • Input: sequences from within and between species
  • Output: reject neutral model (or assumptions of test)
9
Q

Drosophila melanogaster and Adh using the MacDonald Kreitman test:
(4)

A
  • Balancing selection acting on the fast/slow polymorphism (a single aa change)
  • Compare the number of non-synonymous and synonymous changes to the polymorphism and divergence
  • Perform a chi2 test
  • NS favouring aa divergence
10
Q

Dn/Ds = Pn/Ps

4

A
Ds = divergence per syn site
Dn = divergene per non.syn site
Ps = polymorphism per syn site
Pn = polymorphism per non.syn site
11
Q

This formula can be used to answer the..
alpha = 1 - (DsPn/DnPs)
(2)

A
  • The Selectionist/neutralist debate

- alpha is the proportion of aa substitutions that are adaptive