Genes in populations 2 Flashcards
what is a locus?
physical position of a gene or marker among a chromosome
what are alleles?
different forms of a gene
what is the term genotype?
a diploid organism with 2 alleles
what is a homozygote?
two identical alleles
what is a heterozygote?
two different alleles
what is polymorphism?
when a gene or phenotype has more than one form
what is the HWE?
using the allele frequencies in one generation to to predict genotype frequencies in the next generation
what are the 5 assumptions for HWE to work?
1) random mating
2) no natural selection
3) large population size
4) no migration
5) no mutation
give 4 reasons why the HWE is useful?
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
in the example of the peppered moths which is the melanic form and when did it have increased frequency?
the all black moth which increased in frequency in the industrial areas
which allele was dominant the melanic or the typical form?
the melanic allele was dominant
how do you calculate relative fitness when comparing 2 genotypes?
take the most favoured genotype as a standard fitness with level 1.0 and divide the less favoured genotype percentage recapture by the favoured
how do you calculate the selection coefficient and what does it measure?
1 minus the relative fitness of the un favoured genotype , it measures the intensity of selection
what is balancing selection?
a form of selection where heterozygotes and fitter than homozygotes
what is the key step in the life of HIV?
HIV makes enzyme reverse transcriptase which converts single stranded RNA into double stranded DNA form
3 reasons why HIV can develop drug resistance quickly?
it has a high mutation rate, a generation time of 2.5 days and a large population size
how does the size of population affect the loss of genetic variation by drift?
The loss is much faster in smaller populations
what is the problem with populations with small genetic variation?
high extinction risk - less capable of evolving
how can you measure variation within in a population?
with genetic markers
why is heterozygosity 35% lower on average in threatened species?
Because genetic factors are important
what is the standard measure of degree of inbreeding?
wrights inbreeding coefficient
what does the inbreeding coefficient show?
the probability that the individual is IBD for the locus in question
what does the larger the inbreeding coefficient show?
the more inbred
what does IBD stand for?
identical by decent
what are 4 negative consequences of inbreeding?
1) higher frequency of homozygotes
2) reveal recessive harmful alleles
3) less likely to benefit from heterozygote advantage
4) inbreeding depression - lower fitness
what can isolated human populations be used for?
to map disease genes
