chapter 25 deck Flashcards
(17 cards)
Describe the gene pool of a population.
gene pools can be described in terms of genotypic frequencies and allelic frequencies
Calculate genotypic frequencies.
Calculate allelic frequency
genotypic frequency: number of AA individuals with genotype/ number of individuals (how often see specific genotype or allele)
allelis frequencies 2nAA + nAA/ 2N
Give the assumptions and predictions of the Hardy-Weinberg law
Population is Large, Randomly mating, not affected by Mutation, Migration or Natural selection
when the frequncies of the genotypes are in expected proportions, the population is said to be in hardy weinberg equillibrium
Explain the implications of the Hardy-Weinberg law
- a population cannot evolve (reproduction alone will not bring about evolution)
- genotypic frequencies are determines by allelic frequencies
- a single generation of random mating produces the equilibrium freuqncies (natural selection, mutation, migration have not taken place since the last time random mating took place
-when population is not in hardy weinberg equilibrium one of the assumptions has not been met
Distinguish between positive and negative assortative mating (nonrandom)
Negative assortive mating: tendency of unlike individuals to mate
Positive assortive mating: tendency of like individuals to mate
Give the effects of inbreeding on genotypic frequencies
inbreeding: preferential mating between related individuals
inbreeding results in an increase in the proportion of homozygotes and a decrease in the proportion of heterozygotes in a population
Explain why inbreeding depression arises.
Inbreeding depression: increased apperance of lethal and deleterious traits by increasing the probability of producing homozygotes with those traits
Describe the effect of mutation on allelic frequencies
recurrent mutation changes allelic frequencies
Forward and reverse mutations eventually lead to a stable equilibrium at equilibrium the allelic frequencies do not change even the mutation in both directions continues (think of recycling symbol)
Describe the overall effects of migration on allelic frequencies
Results in populations that are not genetically different from one another and helps increase genetic diversity, prevents populations from becoming genetically different from one another, increases genetic variation within populations
Explain the effects of genetic drift on allelic frequencies of populations
There are two causes of genetic drift founder and genetic bottleneck genetic drift is the change in Olympic frequencies the effects of genetic drift are alleles that are just as likely to increase and decrease ,reduction of genetic variations, different populations diverging genetically from one another overtime
Explain what factors influence the magnitude of genetic drift
The size of the population
Describe the causes of genetic drif
There are two causes of genetic drift sampling errors there’s founding affect and genetic bottleneck
founder effect is an establishment of a population comes by a small number of individuals
Genetic bottleneck happens when a population undergoes a drastic reduction in size
Explain the effects of natural selection on allelic frequencies.
Differential reproduction of genotypes
effects on gene pool deepened on the fitness value of the genotypes in the population
Describe how fitness is calculated.
fitness is how many offspring one has
Describe different types of natural selection and their effects
check notes page 418
Explain how natural selection and mutation are opposing forces for detrimental allele
On the one hand, natural selection works to eliminate detrimental alleles from a population over time. This is because organisms with detrimental alleles are less likely to survive and reproduce than those without them. For example, if a gene causes a disease that leads to premature death, individuals with that gene are less likely to pass it on to their offspring, and the frequency of the allele in the population will decrease.
On the other hand, mutations introduce new genetic variation into a population, including new detrimental alleles. Mutations can occur spontaneously or be caused by environmental factors, such as exposure to radiation or toxins. If a new detrimental allele arises and is not eliminated by natural selection, it can become more common in the population over time, potentially causing harm to individuals who inherit it.
Therefore, natural selection and mutation are opposing forces for detrimental alleles. Natural selection works to eliminate them, while mutations introduce new ones.
Summarize the effects of different evolutionary forces on genetic variation within and among populations
Natural selection: acts to increase the frequency of beneficial alleles and decrease the frequency of deleterious alleles within populations. It can also result in differences in allele frequencies between populations that experience different selection pressures.
Mutation: introduces new genetic variation into a population. It increases genetic diversity within populations but does not necessarily lead to differences in allele frequencies between populations.
Genetic drift: is a random process that can cause changes in allele frequencies within populations over time. It can lead to loss of genetic diversity within populations and divergence between populations.
Gene flow: occurs when individuals or their gametes move between populations. It tends to reduce genetic differentiation between populations, homogenizing allele frequencies across them.
Non-random mating: occurs when individuals mate preferentially with certain phenotypes or genotypes. It can lead to changes in allele frequencies within populations, particularly when it results in inbreeding
