Lecture 12 Flashcards
(20 cards)
what is epistatic interactions?
a circumstance where the expression of one gene is modified (e.g., masked, inhibited or suppressed) by the expression of one or more other genes.
what is narrow sense heritability?
the portion of genetic variation that parents can reliably pass on to their offspring
Can parents reliably pass on dominance effects?
- no
- this is because their phenotype depends on the allele of the other chromosome
Can parents reliably pass on epistatic/interaction effects?
- no
- because phenotype depends on the allele at a locus on another chromosome, and recombination and independent assortment during meiosis break up associations between alleles at different loci
Can parents reliably pass on environment effects?
- no
- because phenotype depends on environment of offspring
What does it mean for something to “reliably” pass on?
means the part we are able to predict that will pass on from parent to offspring
What can parents reliably pass on to their offspring, in terms of genetic variation?
additive effects
What does low heritability mean in terms of all of the observed phenotypic variation?
just means a small proportion is caused by variation in genotypes. but it does not mean the trait is not genetically determined, just that there is low variation
Is heritability informative about the nature of between group differences?
no
What are the two things that natural selection involves?
natural selection involves both a within generation process and a between generation process
what is the within generation process?
- phenotypic variation and fitness differences
- not all members of parental generation contribute equally (survival, reproduction, fitness)
What is the between generation process?
- phenotypic selection is coupled with inheritance to produce a genetic response
- combining alleles to form the next generation?
How can we study changes in allele frequencies for natural selection?
using phenotypic selection
what is directional selection?
one allele being favored
what is stabilizing selection?
intermediates in alleles, does not have to be heterozygotes though
what is disruptive selection?
two extreme selection for the heterozygotes
what is the effect of directional selection?
- changes the population mean
- reduces variation, but not substantially
what is the effect of stabilizing selection?
- reduces variatioin
- does not change the mean value in the population
- (losing variaiton means losing the tails on a figure)
what is the effect of disruptive selection?
- increases the variation
- does not alter the population mean value
what could low heritability be due to?
high Vp or low Va
