Variance Flashcards
how can you determine whether a trait is genetic or not? (3)
look at the correlation between siblings (but make sure no maternal effects or environment),
- rare offspring from different parents in the same environment- the difference must be due to genes
- if a trait is heritable it will respond to selection- artificial selection
what frequency must a minority allele be to deem a loci polymorphic?
over 0.01
what is inbreeding depression?
the decrease in fitness of a population due to inbreeding, inbreeding results in a lack of heterozygosity and the value of F increases- this further decreases offspring and affective population size, further increasing inbreeding, small population size also decreases the ability to remove deleterious mutations due to small effective population size.
give an example of inbreeding depression
tay sachs disease is common in a population of jews- this is because jewish people tend to marry jewish people
give an example if inbreeding depression in nature than has shown to be prevented?
a swedish population of adders that consisted of fewer than 40 individuals- lots of homozygous, low fecundity, mutated offspring, scientists added 20 males and removed after 4 generations, increased population size drastically
what is an example of a very heritable trait in nature?
- the fornix bird bill depth= 0.9
- flies phototaxis- two populations diverged greatly when positively or negatively selected for
what is net’s index of genetic distance?
measures how likely it is that gene copies taken from tw populations will be different alleles
in what type of population are the chances of fixation highest?
smaller populations abacus 1/2N
how can the founder effect be viewed in nature?
in northern elephant seal has no variation in 24 loci that code from enzymes. this is because in 1890 the population size was reduced to around 20 due to hunting, and the effective population size was even lower as only 20% of males mate. therefore, genetic drift caused fixation of these genes.
what is the neutral theory of evolutionary change?
that most of the variation seen at the molecular level is due to genetic drift rather than selection- this is supported by the fact that many loci are very polymorphic and natural selecton would not be able to sustain and support such diversity, another argument was that a given portein evolved at similar rates in different lineages. this constancy would not be expected to result from natural selection but would expected if most evoluntionary changes at the molecular level are caused by genetic drift.
what does the study of mitochondrial DNA support?
out of africa theory- study of mitochondrial DNA- there are fewer nucelotide differences amount non african hapoltypes on average than african haplotypes- a study concluded that all human mitochondrial genes both african and non african are decsended from a common ancesteroal gene that existed around 250000 years ago. similar conclusions were reached with the y chromsomes.
