lecture 11

Question 1

what is inbreeding

Answer 1

a form of non random mating
make new assumptions = modify hardy weinberg

Question 2

describe inbreeding - context of crosses

Answer 2

same allele being passed down
mating between first cousins
many possibilityes

Question 3

what is IBD

Answer 3

alleles that are IDENTICAL BY DESCENT (IBD) are one possible outcome
at single locus

Question 4

what inbreeding increase

Answer 4

Probability that 2 alleles at a locus will be copies of an allele present in an ancestor
such copies = IBD - identical by descent

Question 5

what is F coeff

Answer 5

probability of IBD
F quantifies the overall probability that the two alleles inherited by a given individual will be identical by descent

Question 6

how to calculate inbreeding coeff

Answer 6

locate individual and diagram pathway
people in pathway besides final person = n
inbreeding coeff F= (1/2)^n
(if 2 paths = add both coeffs together)
if parent is inbred = modified formula F = (1/2)^n (1+FA), where FA = inbreeding coeff of parent

Question 7

what changes genotype frequencies

Answer 7

inbreeding

Question 8

describe frequencies in changed inbreeding frequencies

Answer 8

in pop that switches over from random mating to inbreeding
fA1A1 = p^2 +Fpq
fA1A2 = 2pq (1-F)
fA2A2 = q^2 + Fpq
more homozygotes and LESS heterozygous
as F increases heterozygous decrease and homozygous increase (if more and more gens = further depart from hardy weinberg)

Question 9

what is inbreeding depression

Answer 9

reduction in viability of inbred individuals

Question 10

why does inbreeding depression happen

Answer 10

bc most deleterious conditions require 2 copies of mutation to be expressed
so more and more diseases expressed
reduces vigor, variablity and reproductive sucess
decline in fitness of average individual

Question 11

what is inbreeding mortality in us

Answer 11

more and more inbred (like the more closely related) = increase infant mortality

Question 12

does inbreeding cause change in allele frequencies

Answer 12

NOOOO
but genotype frequencies do change

Question 13

name factors influencing allele frequencies

Answer 13

mutation
Migration
genetic drift
natural selection

Question 14

describe mutation - factors influencing allele frequencies

Answer 14

ex = Mutations at the Cystic Fibrosis Transmembrane Conductance (CFTR)
locus can lead to Cystic Fibrosis
Particular mutation on chrom 7 cftr gene at base pair level

Question 15

what is a typical rate of mutation per base pair of dna per gen in humans

Answer 15

one in a billion
low rate of mutation depends if talking about gene or nt but still v small

Question 16

how quickly does mutation alone change allele frequencies

Answer 16

mutation rate = 10^-5 per gen
p t+1 = p t (1-u)
veryyyy slowly
mutations alone have small effect

Question 17

describe migration - factors influencing allele frequencies

Answer 17

could be higher than mutations = will change it faster
introduces new allele into group
if unidirectional = like mutation
if bidirectional = homogenizes population= does not diverge

Question 18

describe genetic drift - factors influencing allele frequencies

Answer 18

small pops - just drifting
if large pop = not drift as much
small pop = can diverge quickly from hardy weinberg - loss of fixation of genetic alleles, diverges from each other in allele frequencies, wild fluctuations in allele freq

Question 19

where is random genetic drift weakest and explain

Answer 19

large population= no extreme genetic drift
small pop= divergence from one another and loss of genetic diversity
if have high migration = populations would diverge less quickly since slows down loss of alleles since creates larger pop

Question 20

describe population bottlenecks

Answer 20

smaller neck into bigger bottle = wont contain same proportions as small bottle

Question 21

describe island colonization from mainland

Answer 21

founding pop from larger pop
pop smaller for individual islands = could lead to genetic drift can end up with diff composition - can lead to bottleneck effect

Question 22

describe population crashes

Answer 22

hare population grows and lynxs follows
if lynxs grow a lot = hare as food goes down = now lynx crashes
sort of bottleneck event
overtime pop represents genetic mean = closer to smaller pop (human pop looks smaller genetically -diversity)

Question 23

describe ex of genetic drift - retinitis pigmentosa

Answer 23

regular = 1/2000 individuals have diseases usually but
tristan de cuhna island = frequency 10-20 times higher since one pop has more of it

Question 24

describe ex of genetic drift - CF

Answer 24

Average Cystic Fibrosis incidence worldwide (1 out of 2,500), but in Saguenay region of Quebec (1 out of 936)
large fluctuation in allele frequency

Question 25

What else happen in populations that are kept small for generation after generation?

Answer 25

loses variation and increases inbreeding coeff
inbreeding levels building up fast in smaller pop

Question 26

what can habitat fragmentation do

Answer 26

reduce population sizes
natural lanscape divided up into smaller and smaller fragments
leads to small pop size - no migration between habitats
more and more rare alleles being lost - lose genetic diversity
like adaptations for global warming lost = cannot survive well, so small population disadvantaged

Question 27

describe small populations and the extinction vortex

Answer 27

small pop leads to small pop
could have effect on size of future pop
inbreeding leads to reduction of health, individual fitness and inability to adapt, possible feedback loop
each gen = worse = lost more variability and suffers from inbreeding depression = extinction vortex

Question 28

what happens if homozygous selected against

Answer 28

bad like purging
selecting against = both inbreeding and selection