BIOL 290 Chapter Notes - Chapter 2: Allele Frequency, Panmixia, Gene Pool

I need this in 15 min!Please help!!!1

A gene in a population of sexually reproducing organisms with the following genotype frequencies is at Hardy-Weinberg Equilibrium: BB 100, Bb 800, bb 100

A) true B)false C) can not be determined

Which of the following evolutionary forces would be the best explanation for the genotype frequencies in the population in the above question?

A) genetic drift B) there are no evolutionary forces acting on this gene population C)assortive mating D) Overdominance E)Directional selection

If a population is at Hardy-Weinberg equilibrium, which of the following allele frequencies would yield the smallest number of heterozygotes? A)

A=0.25, B=0.75 B) A=0.75, B=0.25

C)A=0.50, B=0.50

D)A=0.10, B=0.90

Fixation occurs when one allele becomes the only allele for a gene in a population, meaning that all other alleles for that gene have been lost. True or false

1. A population of 100 slugs randomly mates except for 18 selfbreeding individuals. The population has a gene for darkmottling colour, M, which produces dark individuals when ahomozygous MM condition exists, and green individuals when ahomozygous M’M’ condition exists. Heterozygotes are mottled. What is the proportion (genotypic frequency) of the dark, mottled,and green slugs in the succeeding generation of thispopulation? The initial allele frequency of M is 0.7 and ofM' is 0.3.

b) Not all populations experience equal amounts of geneticdrift or non-random mating. Evolutionary biologists use theeffective population size, N_e, to estimate the size ofan ideal population that would undergo the same amount ofgenetic drift or show effects of non-random mating as theactual population. Smaller populations have more drift. The value of N_e can be determined from:

N_e = 4 N_mN_f / N_m +N_f

Where N_m is the number of males in the actual population andN_f is the number of females.

If one population of elkhas 2 males and a harem of 6 females and another population in thesame

region has 1 male and 11females. Which population is more likely to experiencegenetic drift? Why?

(keywords to look up: Sewall Wright, effective population size, andFisherian ratio)

Q1. What is the founder effect?

Sampling error that occurs during the establishment of a newpopulation by a small number of migrants.

Strong natural selection acting on the founders of a newpopulation because the environment they are now living in is sodifferent from the environment they came from.

A phenomenon named after William Founder, who observed that toppredators generally have low genetic diversity.

Rapid population growth following a bottleneck.

Q2. The effects of genetic drift are more pronounced in largerpopulations.

True

False

Q3. Inbreeding tends to increase the proportion of homozygousindividuals in a population (i.e. individuals that have two copiesof the same allele).

True

False

Q4. The effective size of a population is:

The size of an idealized randomly-mating population that is notunder selection and has the same heterozygosity as the actualpopulation.

The size of an idealized randomly-mating population that has thesame heterozygosity as the actual population, but does not loseheterozygosity over time.

The size of an idealized randomly-mating population losinghomozygosity at the same rate as the actual population.

The size of an idealized randomly-mating population losingheterozygosity at the same rate as the actual population.

Q5. Which of the following tends to reduce the effective size ofa population?

Check all that apply:

Increasing the population size.

A biased sex ratio.

Non-random mating.

Q6. If gametes from a gene pool combine randomly to make only asmall number of zygotes, the allele frequencies among the zygotesmay be different than they were in the gene pool because:

The effects of natural selection are more pronounced in smallpopulations.

The effects of genetic drift over several generations are morepronounced with small numbers of gametes.

The effects of differences in frequencies for different allelesare more pronounced with small numbers of zygotes.

The effects of sampling error are more pronounced with smallsamples.

Q7. Genetic drift is different from natural selectionbecause:

In natural selection allele frequencies change because somealleles confer higher fitness, whereas in genetic drift allelefrequencies change because of chance sampling error.

Natural selection acts primarily in large populations, whereasgenetic drift acts primarily in small ones.

Natural selection is a mechanism of evolution, whereas geneticdrift is an outcome of evolution.

Natural selection tends to cause rapid evolution, whereasgenetic drift tends to cause slow evolution.

Q8. Imagine a population evolving by genetic drift in which thefrequency of allele K is 0.65. What is the probability that at somepoint in the future allele K will drift to a frequency of 1?

Q9. A dwindling population of 1000 frogs occupies an isolatedwatershed in Costa Rica. To help preserve the species, scientistscaught 20 frogs to start a new population in a nearby watershed.This species has a gene that affects eye shape. The 1000-memberwild population has two alleles for this gene: R and r, withfrequencies 0.7 and 0.3, respectively. What will be the allelefrequencies of R and r in the 20-member founder population?

The frequencies will be 0.7 for R and 0.3 for r.

The frequencies will be 1.0 for R and 0 for r.

The expected frequencies are 0.7 for R and 0.3 for r. The actualfrequencies could be different.

The founder populations's allele frequencies will necessarily bedifferent than the source population's frequencies.

Q10. For a population containing 90 females and 10 males, whatis the effective population size, N_e ?