Population genetics

Question 1

species

Answer 1

a discrete, reproductively defined system of populations with a common evolution

Question 2

population

Answer 2

a group of animals of one species which interbreed (particular area)

Question 3

gene pool

Answer 3

set of genes and/or alleles in the entire population

Question 4

breed

Answer 4

a population distinguishable from another of the same species by frequencies of genes, chromosomal variation, or hereditary phenotypic characteristics

Question 5

population genetics

Answer 5

allele frequencies of a population of animal
-ig what is the frequency of the polled allele in french, canadian, world wide charolais

Question 6

what does it mean if genes are fixed

Answer 6

in some species some genes are fixed meaning all animals are homozygous for the same allele

Question 7

hardy-weinberg equilibrium

Answer 7

p+q=1
p=the proportion of the dominant allele
q=the proportion of the recessive allele

Question 8

1AA : 2Aa : 1aa in pq

Answer 8

p^2 : 2pq : q^2

Question 9

hardy-weinberg eq allele frequencies

Answer 9

-q^2=fq of autosomal res
-q=vq^2=frequency of recessive allele
-1-q=p=frequency of dominant allele not that frequency of individuals with dominant phenotype is p^2+2pq (not just p^2)
-q^2 = frequency of individuals with recessive genotype

Question 10

if you have the frequency of autosomal recessive homozygote how do you get the frequency of recessive alleles

Answer 10

q=square root of q^2
-ie. if 35% of the canadian charolais are horned (recessive to polled) what is the gene frequency of the horned allele q^2=0.35 q= square root 0.35=0.59 so freq of horned allele is 59

Question 11

on a gene frequency graph what are the trends youd see

Answer 11

-homozygote increases exponentially with gene frequency
-heterozygotes dont exceed 50%
-rare alleles occur predominantly in heterozygots

Question 12

for the hardy-weinberg eq gene frequencies stay stable if:

Answer 12

-mating is random
-no selection
-no mutation
-large population

Question 13

domestic animal breeding and hardy-weinberg

Answer 13

-humans select which animals to breed
-wild choose them self
-hardy-weinberg eq equation works well for wild animals but must be domesticated for wild animals
-in domestic animals without random breeding we must modify calculations of gene frequency, if phenotypic selection is used
-ie. if we want to fix polled in a charolais herd

Question 14

snyders ratio

Answer 14

-based on phenotype i.e. rarely know genotype of animals for dominant trait
-used to determine proportion of recessive or dominant offspring per parental mating type

Question 15

snyders ratio for dominant x dominant

Answer 15

-parents could be:
-Dd X Dd=2pq x 2pq
-DD x Dd=p^2 x 2pq
-DD x DD=p^2 x p^2
-only Dd x Dd produce dd offspring therefore 1/4 dd of (2pq x 2pq)
-=1/4 dd

Question 16

snyders ratio

Answer 16

-recessive phenotype offspring/total from dominant x dominant
-=(q/1+q)^2

Question 17

what is snyders ratio based off

Answer 17

-phenotype (rarely know genotype of animal for dominant trait

Question 18

snyders ratio for dominat x dominant

Answer 18

dom 1-(q/1+q)^2
res (q/1+q)^2

Question 19

syders ratio for dominant x recessive

Answer 19

dom 1-(q/1+q)
res (q/1+q)

Question 20

syders ratio for rec x rec

Answer 20

dom: 0
rec: 1

Question 21

for dominant x rec what could parents be

Answer 21

Dd X dd=p^2 x q^2
DD x DD=2pqxq^2

Question 22

genetic drift

Answer 22

-small subpopulations become increasingly different over generations
-e.g. rabbit population
-p and q freq changes in each generation
-by chance the q allele is lost by 3rd generation

Question 23

effects of population size on genetic drift

Answer 23

-pop size influences the allele frequency changes or “drift”
-fluctuates more in smaller populations

Question 24

founder effect

Answer 24

-founding population (herd) is small
-wild: gene frequency changes are due to chance

Question 25

founder effect example: SCID arabians

Answer 25

-severe combined immuodeficency
-autosomal recessive (cc)
-in england: q^2=0.01 or 1% of arabs
-q=1
-australia: 2 stallions from england purchased
-both carriers: Cc
-q=0.5
-17/204=8.3% affected foals born

Question 26

breed introduction

Answer 26

-example of founder effect
-“exotic” cattle to canada
-holstein to canada
-llamas to cali
-relatively small # of animals “found” the population
-“new” population could be very different form parent population in terms of gene frequency

Question 27

closed herd example

Answer 27

-swine companies such as:
-HyPor
-founded their canadian branch with 1 shipment of british stock

Question 28

population bottle neck

Answer 28

-example of genetic drift
-population is severely reduced in numbers for 1 or more generations
-decrease can be caused by a natural desaster
-start w good mix—> more of one then the other

Question 29

show ring and AI impacts

Answer 29

-promotes “few” select sires
-these are used extensively
-i.e disproportionally
-20 years ago: 1 salers bull was present in >70% of pedigrees

Question 30

panmictic populations

Answer 30

-random matings in breeding population
-exchange of breeding animals

Question 30

gene flow

Answer 30

-exchange of new alleles between subpopulations
-panmictic populations
-genetic isolates

Question 31

gene isolates

Answer 31

-subpopulation breeds only within itself
-“closed” herd

Question 32

cline

Answer 32

-phenotypic gradients across a geographical region
-gene flow is greatest between adjacent populations

Question 33

migration

Answer 33

-migration of wild animals could be from their own movement
-in domestic animals, migration can include: purchase, trucking to new barn, ranch, etc…

Question 34

gene flow implies migration therefore…

Answer 34

gene frequencies change
-typically, the small population (“island”) recives immigrant animals from the large population (“mainland”)

Question 35

how is migration different in wild animals vs domestic

Answer 35

-for wild animals it is typically some males and some females
-migration in domestic animals is usually buying a few new males

Question 36

what can import and export regulations do to migration

Answer 36

-can halt migration

Question 37

what does gene flow (migration) allow for

Answer 37

assure a constant source of genetic variation
-retards randome drift
-allows spread of new neg or pos mutation

Question 38

how do domestic animals breeds vs presarvationists differ

Answer 38

-domestic animal breeders want change
-perservationists want no change

Question 39

hardy-weingberd eq mating is random

Answer 39

-assortative mating
-pos: means both mates have “same” trait
neg: means the two mates do not have the “same” trait
-AI
-showring winners

Question 40

dominance hirrachy in animals

Answer 40

-older or dominant male mates mots females

Question 41

assortative mating affects co-dominant alleles (not breeding like to like)

Answer 41

-horses
-mating two opposite homozygotes to accive the heterozygote
-sorrel x cremello–> palomino

Question 42

hardy weinburg eq no migration examples for domestic animals

Answer 42

-cattle purchase new bulls (keep heifer replacements)
-horses (stables may be founded by one stallion, but buy mares)
-poultry (total in-total out)
-pigs (both sexes burchased)

Question 43

hardy weinburg eq no mutation

Answer 43

mu=mutation rate
-normally very low (we arent trying to mutate)
-no attempt to increase this (can come up and be good)

Question 44

hardy werinburg a large population