population genetics

Question 1

locus

Answer 1

physical position of a gene or marker along a chr.

Question 2

allele

Answer 2

different form of a gene

Question 3

genotype - diploid

Answer 3

made up of 2 alleles

Question 4

homozygote

Answer 4

2 identical alleles

Question 5

heterozygote

Answer 5

two diff. alleles

Question 6

polymorphism

Answer 6

gene or phenotype with more than one form

Question 7

what does population genetics study and why?

Answer 7

freq. of alleles
what determines genetic composition
genetic disease - basis, history, freq.

Question 8

what do p and q stand for in HWE

Answer 8

each allele in a population

Question 9

HWE observes that…

Answer 9

independently observed allele freq. can be used to predict next gen.

Question 10

HWE assumes:

Answer 10

Random mating
No natural selection
A large population size
No migration
No mutation

Question 11

what does HWE show?

Answer 11

how genetic variation is maintained

Question 12

which gene mutated in peppered moths

Answer 12

cortex gene

M (melanic mutant) dominant to + (peppered WT)

Question 13

Bernard Kettlewell exp.

Answer 13

mark and recapture peppered moths in rural areas and outside Birmingham
recaptured more better adapted moths as others were eaten

Question 14

relative fitness equation

Answer 14

reproductive/ survival rate of each genotype
___________________________________
highest reproductive/ survival rate of one genotype

Question 15

selection coefficient equ.

Answer 15

highest rel. fitness (1.0) - rel. fitness of other genotype

Question 16

positive selection

Answer 16

when one allele has an advantage over the other

loss of variation

Question 17

where is coat colour gene in rock pocket mice

Answer 17

MCR1
dark (D) is dominant - DD Dd
light (d) is recessive - dd

Question 18

HIV drug resistance, mutation, drug, time, why, how is it overcome

Answer 18

drug - 3TC , takes 4 months
mutation - 184th amino acid, reverse transcriptase Ez resistant
HIV has high mutation rate - 2.5 day gen. time = large population and lots of new mutations
administer 2+ drugs at once

Question 19

recombination (HIV)

Answer 19

new combinations of alleles produced
RT switches between genomic templates in replication (similar branches on a phylogenetic tree combine)
HIV is resistance to both drugs

Question 20

recombination (HIV)

Answer 20

new combinations of alleles produced
RT switches between genomic templates in replication (similar branches on a phylogenetic tree combine)
HIV is resistance to both drugs

Question 21

sickle-cell anaemia mutation and genotype

Answer 21

recessive mutation in B-hb gene
heterozygote selected for and maintained in population as helps with malaria resistance
departs from HWE as more heterozygotes (SA) than expected

Question 22

balancing selection

Answer 22

heterozygotes are fitter than homozygotes
e.g. sickle cell anaemia
maintains variation

Question 23

kuru prion disease

Answer 23

mutation at PRNP gene
under balancing selection when Kuru was present
know this because women not exposed are in HWE but women that were aren’t (selection happening) and heterozygote is fittest

Question 24

genetic drift in small populations

Answer 24

process of losing genetic variation by chance
faster than in bigger
small populations are less polymorphic (fewer phenotypes)

Question 25

genetic variation in elephant seals

Answer 25

northern populations smaller due to human exploitation
southern seals should have more genetic variability
northern seals had a genetic bottleneck

Question 26

endangered species have ….. genetic variability

Answer 26

low
often due to population bottlenecks
increases risk of extinction as less genetic variation

Question 27

heterozygosity in threatened species

Answer 27

should be lower in over 50% paired comparisons if genetic factors are important
true - heterozygosity is 35% lower in threatened species

Question 28

alleles are identical by descent if…..

Answer 28

have same ancestral allele

Question 29

inbreeding coefficient

Answer 29

probability of inheriting two alleles that are identical by descent
can range from 0-1
work out by doing (1/2)^no. individuals in inbreeding path

Question 30

If the alleles at a locus are ibd, the locus must be…

Answer 30

homozygous

Question 31

inbreeding in a small population leads to…

Answer 31

loss of genetic variation, lowered evolutionary potential, compromised reproductive fitness, elevated extinction rate

Question 32

californian condor

Answer 32

lethal recessive allele reached p=0.17 after bottleneck of genetic variation
homozygous birds die at hatching (chondrodystrophic dwarfism)

Question 33

florida panther

Answer 33

roadkill = low gen. var.
male cats have undescended testes and poorest sperm count of all cats (cryptorchidism)
bred with females from closely relating species to inc. gen. var.

Question 34

koalas

Answer 34

bad recovery program
succession of bottlenecks (3)
lots of koalas have no balls

Question 35

isolated populations

Answer 35

allow us to ID disease causing genes
e.g. Amish people
high incidence of Ellis-van Creveld syndrome: dwarfism, polydactyly and heart defects