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UBC BIOL 121 Practice Questions and Correct Answers

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  • BIO 121

Gene pool all of the alleles of all the genes in a certain population Hardy-weinberg principle genotype frequencies in a large population do not change from generation to generation in the absence of evolutionary processes Claims of hardy-weinberg principle (1) if the frequencies of alleles a1 an...

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  • August 13, 2024
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  • BIO 121
  • BIO 121
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UBC BIOL 121 Practice Questions and
Correct Answers
Gene pool ✅all of the alleles of all the genes in a certain population

Hardy-weinberg principle ✅genotype frequencies in a large population do not change
from generation to generation in the absence of evolutionary processes

Claims of hardy-weinberg principle ✅(1) if the frequencies of alleles a1 and a2 in a
population are given by p and q, then the frequencies of genotypes a1a1, a1a2, a2a2
will be given by p^2, 2pq, and q^2 for generation after generation.
(2) when alleles are transmitted via meiosis and random combination of gametes, their
frequencies don't change over time.

Assumptions of hardy-weinberg principle ✅no natural selection at gene in question
No genetic drift, or random allele frequency changes, affecting the gene in question
No gene flow
No mutation
Random mating with respect to the gene in question

Genetic variation ✅number and relative frequency of alleles present in a particular
population; the proportion of phenotypic variation in a trait that is due to genetic rather
than environmental influences

Directional selection ✅favours one extreme phenotype with the result that the average
phenotype of a population changes in one direction; generally reduces overall genetic
variation; if continues over time will result in the loss and fixation of alleles

Purifying selection ✅when disadvantageous alleles decline in frequency

Stabilizing selection ✅favours phenotypes near middle of range of phenotypic
variation; reduces genetic variation; no change in average value of the trait over time

Disruptive selection ✅eliminates phenotypes near the average value and favours
extreme phenotypes; genetic variation is maintained

Balancing selection ✅no single allele is favoured, balance among alleles in terms of
fitness and frequency

Frequency-dependent selection ✅certain alleles are favoured when they are rare, not
when common

, Heterozygote advantage ✅heterozygote individuals have higher fitness than
homozygote individuals

Genetic drift ✅any change in allele frequencies due to chance
Random with respect to fitness
Most pronounced in small populations
Over time, can lead to random loss or fixation of alleles

Founder effect ✅change in allele frequencies that occurs when a new population is
established

Genetic bottleneck ✅sudden reduction in number of alleles in a population; drift occurs
during and causes change in allele frequenices

Gene flow ✅movement of alleles from one population to another
Random with respect to fitness
Increases similarity of allele frequencies in source and recipient population, making
them more alike

Mutation ✅dna polymerase makes an error as it copies a dna molecule -> change in
sequence
Increases genetic diversity
Random with respect to fitness
Slow compared w/ selection, genetic drift, and gene flow as an evoluationary
mechanism
Introduces new alleles into every individual in every population

Deleterious mutation ✅alleles that lower fitness

Beneficial mutation ✅alleles that higher fitness

Inbreeding ✅increases homozygosity
Doesn't cause evolution, can speed rate of evolutionary change
Changes genotype frequencies not allele frequencies
Increases rate at which purifying selection eliminates recessive deleterious alleles from
a population
Mating between relatives

Inbreeding depression ✅decline in average fitness
Results from many recessive alleles represent loss of function mutations or many genes
are under intense selection for heterozygote advantage

Assortive mating ✅mating is nonrandom with respect to specific traits

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