BILD 3 Chapter Notes - Chapter 21: Allele, Allele Frequency, Mendelian Inheritance

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byzantiumfly635

30 May 2016

School

UCSD

Department

Biology/Lower Division

Course

BILD 3

Professor

Sarah Stockwell

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Document Summary

A population is a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. Different populations of a single species may be isolated geographically from one another, exchanging genetic material only rarely. Characterize a population"s genetic makeup by describing its gene pool. Consists of all copies of every type of allele at every locus in all members of the population. Fixed in the gene pool occurs when only one allele exists for a particular locus in a population. To assess whether natural selection or other factors are causing evolution at a particular locus is to determine what the genetic makeup of a population would be if it were not evolving at the locus. The gene pool of a population that is not evolving can be described by the hardy-weinberg principle.

Related Questions

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 ?

chocolateplatypus914

Q1. What are alleles?Different forms of the same gene.Different genes.The different characteristics of an organism.Genes found only in humans.Q2. If you add up the frequency of homozygotes + the frequency of heterozygotes for one gene (i.e. at one locus) in a population, what number do you get?Q3. People who are heterozygous for the sickle-cell allele:Are susceptible to malaria but not sickle-cell anemia.Are susceptible to sickle-cell anemia but not malaria.Are not susceptible to either sickle-cell anemia or malaria.Are susceptible to both sickle-cecell anemia and malaria.Q4. In the case study in this lab, which genotype is represented by "2pq" in the Hardy-Weinberg equation?Homozygous HbAHomozygous HbSHeterozygous HbA/HbSNo specific genotypeQ5. Suppose that, in an isolated village, the proportion of individuals that have sickle-cell anemia is 0.1 (or 1 of every 10 people). What proportion of the population should be sickle-cell carriers, according to Hardy-Weinberg expectations?Q6. When you simulated the elimination of malaria at the beginning of the lab, once the allele frequencies stabilized, what was the frequency of the HbA allele?Q7. When you investigated regional differences, what was the frequency (over many generations) of the HbS allele in the village in the "slightly wet" part of Africa?Q8. What is the number of deaths due to sickle-cell anemia in a region without mosquitoes expected to be?Very lowVery highModerateRelated to the frequency of malaria allelesQ9. As long as there are multiple alleles of a gene in a population, why will the frequencies of the alleles always change over time?Because natural selection changes all allele frequencies in populations over time.Because genetic drift causes random fluctuations of allele frequencies in populations.Because diseases will eliminate some of the alleles, generating fluctuations in their frequencies.Because allele frequencies fluctuate before the alleles eventually become fixed.Q10. Imagine a huge population with a gene that has ten functionally equivalent, neutral alleles. A small but genetically representative group of individuals from the big population is transported to an island, forming a small population. Which of the statements below best describes what will likely happen over time, and why?Because natural selection doesn't act on neutral alleles, the frequencies in the two populations should remain the same over time.Genetic drift will cause one allele to first become fixed in the island population, and later to become fixed in the original, large population.Genetic drift will result in the allele frequencies of the two populations diverging over time, with alleles being lost sooner in the island population.The allele frequencies of the two populations will change similarly due to a combination of genetic drift natural selection.

indigosnake469

1. Scientists found that different beak shapes lead to differentmating songs in Darwin's finches. This result best supports whichhypothesis?

	A. Darwin's finches are not different species according to theBiological Species Concept.
	B. Behavioral isolation in Darwin's finches is unrelated to beakshape.
	C. Adaptation to different food sources likely occurred afterreproductive isolation in Darwin's finches.
	D. Adaptation to different food sources indirectly led tobehavioral isolation in Darwin's finches.

2. Which of the following could occur if two partiallyreproductively isolated populations become sympatric? Check allthat apply.

	A. Gene flow between the populations will occur
	B. The populations may eventually become separate speciesthrough reinforcement
	C. The populations will continue to be partially reproductivelyisolated
	D. The populations may eventually lose their geneticdistinctiveness
	E. Hybrids will be inviable or infertile

3. In which population would the rate of genetic drift be thegreatest?

	A large population that is geographically isolated from itsparent population
	A small population that is geographically isolated from itsparent population
	A large population that is not completely geographicallyisolated from its parent population
	A small population that is not completely geographicallyisolated from its parent population

4. Indicate true or false that the following organisms would beconsidered separate species according to the biological speciesconcept. (T/F)

1. Lions and tigers can interbreed successfully to produce viable,fertile offspring, but lions live in open grasslands and tigerslive in dense forests. (T/F)
2. Black bears in the United States can have coat colors rangingfrom blonde to jet black, but bears with different coat colorsoccupy the same habitat and interbreedsuccessfully. (T/F)
3. Many leopard frogs in the eastern United States look the sameand can mate to produce a fertilized egg, but the embryo does notdevelop past the early stages. (T/F)
4. Many of Darwin

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BILD 3 Chapter Notes - Chapter 21: Allele, Allele Frequency, Mendelian Inheritance

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