13. Population and Statistical Genetics Flashcards
Hardy Weinberg Equilibrium
describes the frequency of a gene mutation in a population
what are the assumptions of the Hardy Weinberg Equilibrium
- large population
- random mating
- no new mutation
- no natural selection
- no migration
- no inbreeding
what does “q” represent in the HWE
q = disease or mutant allele frequency
what does “p” represent in the HWE
p = normal allele frequency
because each person has two alleles, what are their frequencies
(p + q)^2 = 1
or
p^2 + 2pq + q^2 = 1
what does “p squared” represent in HWE
p^2 = non-carrier people
what does “2pq” represent in the HWE
2pq = carrier people
what does q squared represent in the HWE
q^2 = affected people
in humans if there are 500 DNA samples taken how many alleles have been taken
1000 alleles
(diploids)
Why does Hardy Weinberg not work with a small population ?
in a small group if one carrier dies the trait will be lost from the small group
why does Hardy Weinberg not work in a population bottleneck
Radical decrease in population size can increase or decrease gene frequency
- small group of migrants
- ethnic cleansing
- plague
how does non-random mating affect the Hardy Weinberg
When mating is non-random individuals select mates based on certain traits. This can cause certain alleles to become more or less common in the population than they would be under random mating conditions.
Why does the Hardy Weinberg not allow for new mutations
By assuming no mutation, the principle helps isolate and examine the effects of other factors on the genetic structure of populations. This makes it easier to identify when and how real populations deviate from Hardy-Weinberg equilibrium
Why does Hardy Weinberg not allow for natural selection
allows us to set up a baseline scenario where all alleles are equally likely to be passed on to the next generation
why does Hardy Weinberg not allow for migration
because migration can mix up the genetic pool by bringing in bringing in new genes or changing the frequency of already existing genes
What is consanguinity
relationships between family members
it will increase or decrease frequency of disease in a population
what are the clinical symptoms of Nail Patella Syndrome
- no knee cap
- nails do not grow properly
what is linkage
tendency of genes that are close together on the same chromosome to be inherited together
What did Sylvia Lawler and Jim Renwick do in the 1950s
- calculated probability that blood group occurred and segregated with NPS by chance
- mathematical probability of the two phenomena coinciding was very small
- NPS and blood group were linked
when are two loci linked
two loci are linked if alleles at these loci do not segregate independently in meiosis
what is a locus
a genetic region on a chromosome
what is an allele
a specific genetic variant
how does Linkage contradict Mendel’s third law
Linkage contradicts Mendel’s third law because it demonstrates that certain genes are not inherited independently when they are physically close to each other on the same chromosome.
what is linkage disequilibrium
the association of two genetic alleles across a population
how would you study linkage disequilbrium
count alleles in the population and compare expected and observed
Bayes Theorem
takes into account information that we already had, modifies this risk with new information
