Exam 2 Flashcards
allele frequencies
rates of occurrence of alleles in a population
= number of specific allele/ total # of alleles in population
fixed allele
when a population exhibits only one allele
fitness
number of offspring that are able to reproduce
modern synthesis
ronald fisher’s formed a synthesis between mendelian genetics and darwin’s theory of natural selection
positive selection
natural selection that increases the frequency of an allele
negative selection
natural selection that decreases the frequency of an allele
balancing selection
maintenance of multiple alleles; acts to maintain two or more alleles in a population
ex: heterozygote advantage over homozygotes
stabilizing selection
maintains the status quo and acts against extremes ex: birth weight
directional selection
leads to a change in the trait over time
ex: artificial selection: competitive element is removed.
disruptive selection
operates in favor of extremes and against intermediates
migration
the movement of individuals from on population to another resulting in gene flow
gene flow
movement of alleles from one population to another
genetic drift
random changes in allele frequencies from generation to generation; significant in small populations
bottleneck
when an originally large population falls to just a few individuals
founder event
a few individuals start a new population
SNP
single nucleotide polymorphism; each nucleotide pair is common enough in the population to be present in a random sample of 50 diploid individuals;
eye color associated with this
sexual selection
promotes traits that increase an individual’s access to reproductive opportunities
intrasexual selection
focuses on interactions between individuals of one sex
intersexual selection
focuses on interactions between females and males
species
individuals that can exchange genetic material through interbreeding; share alleles with each other
gene pool
all alleles present in all individuals in the species
Hardy Weinberg Conditions
- no difference in reproductive success 2. no fluctuation in population 3. no mutations 4. population must be large 5. Individuals must mate at random
inbreeding depression
a reduction in the childs fitness caused by the homozygosity of deleterious recessive mutations
autosome
non sex chromosome
epistasis
multiple genes act in the same pathway to affect a trait
linkage mapping
frequency of recombination used as a measure of the physical distance between genes
timescale of evolution
- generation time of organism 2. strength of selection 3. starting frequency of selected allele- T, S,SF
reciprocal crosses
male and female are switched genotypes to determine whether the gene is sex linked.
should be no difference in F! generations if not sex linked
recombinant frequency
= (# recombinants)/(total # of offspring) x 100
50 or more map units apart= act like on different chromsome
greater chance of physical distance
greater chance of crossover
relative fitness
= (# of offspring with genotype 1)/(# of offspring of genotype 2)
genotype 2 must be the highest fitness in the population
anisogamy
gametes of different sizes
males- make many, small gametes
females- make fewer, larger gametes
sexual dimporphism
differences between the sexes in traits often related to attracting and obtaining mates
