Genes in populations 2

Question 1

what is a locus?

Answer 1

physical position of a gene or marker among a chromosome

Question 2

what are alleles?

Answer 2

different forms of a gene

Question 3

what is the term genotype?

Answer 3

a diploid organism with 2 alleles

Question 4

what is a homozygote?

Answer 4

two identical alleles

Question 5

what is a heterozygote?

Answer 5

two different alleles

Question 6

what is polymorphism?

Answer 6

when a gene or phenotype has more than one form

Question 7

what is the HWE?

Answer 7

using the allele frequencies in one generation to to predict genotype frequencies in the next generation

Question 8

what are the 5 assumptions for HWE to work?

Answer 8

1) random mating
2) no natural selection
3) large population size
4) no migration
5) no mutation

Question 9

give 4 reasons why the HWE is useful?

Answer 9

1) provides a description for how genetic variation is maintained
2) shows how blending inheritance does not happen
3) departures from HWE mean that some assumptions are not met - promotes investigations into why
4) useful in medical genetics to work out carrier frequencies

Question 10

in the example of the peppered moths which is the melanic form and when did it have increased frequency?

Answer 10

the all black moth which increased in frequency in the industrial areas

Question 11

which allele was dominant the melanic or the typical form?

Answer 11

the melanic allele was dominant

Question 12

how do you calculate relative fitness when comparing 2 genotypes?

Answer 12

take the most favoured genotype as a standard fitness with level 1.0 and divide the less favoured genotype percentage recapture by the favoured

Question 13

how do you calculate the selection coefficient and what does it measure?

Answer 13

1 minus the relative fitness of the un favoured genotype , it measures the intensity of selection

Question 14

what is balancing selection?

Answer 14

a form of selection where heterozygotes and fitter than homozygotes

Question 15

what is the key step in the life of HIV?

Answer 15

HIV makes enzyme reverse transcriptase which converts single stranded RNA into double stranded DNA form

Question 16

3 reasons why HIV can develop drug resistance quickly?

Answer 16

it has a high mutation rate, a generation time of 2.5 days and a large population size

Question 17

how does the size of population affect the loss of genetic variation by drift?

Answer 17

The loss is much faster in smaller populations

Question 18

what is the problem with populations with small genetic variation?

Answer 18

high extinction risk - less capable of evolving

Question 19

how can you measure variation within in a population?

Answer 19

with genetic markers

Question 20

why is heterozygosity 35% lower on average in threatened species?

Answer 20

Because genetic factors are important

Question 21

what is the standard measure of degree of inbreeding?

Answer 21

wrights inbreeding coefficient

Question 22

what does the inbreeding coefficient show?

Answer 22

the probability that the individual is IBD for the locus in question

Question 23

what does the larger the inbreeding coefficient show?

Answer 23

the more inbred

Question 24

what does IBD stand for?

Answer 24

identical by decent

Question 25

what are 4 negative consequences of inbreeding?

Answer 25

1) higher frequency of homozygotes
2) reveal recessive harmful alleles
3) less likely to benefit from heterozygote advantage
4) inbreeding depression - lower fitness

Question 26

what can isolated human populations be used for?

Answer 26

to map disease genes