PCB 4674 Lecture Notes - Lecture 11: Allele Frequency, Genotype Frequency, Zygote

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orchidbeaver616

29 Oct 2016

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Evolutionary implications: if two loci in an ideal population are in linkage equilibrium . Chromosome frequencies will not change across generations: if two loci in an ideal population are in linkage equilibrium then chromosome frequencies will change across generations. Hardy-weinberg for two loci: similar to previous hw, except now we will track chromosome frequencies rather than allele frequencies, consider two loci, a and b. With two alleles each, a and a, b and b. No dominant recessive relationship: now consider an ideal population in which the four possible chromosomes exist at frequencies gab, gab, gab, and gab. Lets make some zygotes: pick one egg at random and it is ab. Probability of this happening is gab: now pick a sperm at random and it is also ab. Probability of this happening is gab: but the probability of picking ab egg and ab sperm, which is what is required to make an ab/ab zygote, is the product of the individual probabilities.

Related Questions

Under the Hardy-Weinberg model, a population will reach Hardy-Weinberg frequencies in a single generation. This model assumes that genotype frequencies are the same in both sexes: Consider a situation where this is not the case. A researcher creates a new Drosophila population by selecting 2000 males from a stock population fixed for the dominant A allele at a neutral locus A and 2000 females from a different stock population fixed for the recessive a allele at the A locus. The A allele is located on an autosome, not a sex chromosome. These individuals then mate among themselves.

a) Assuming that there is no mutation, what genotype frequencies will be observed in the first offspring generation?

b) How long will it take this population to reach Hardy-Weinberg proportions?

c) Explain why this population took two generations instead of one to reach Hardy-Weinberg equilibrium.

oliveeagle546

Q5. A sunflower population in Hardy-Weinberg equilibrium has the following allele frequencies for petal color: 0.75 dominant, 0.25 recessive. If the assumptions of Hardy-Weinberg equilibrium continue to hold, then after 200 generations:

The allele frequencies will be: 0.75 dominant and 0.25 recessive.

The allele frequencies will be: 0.50 dominant and 0.50 recessive.

The allele frequencies will be: 1.0 dominant and 0 recessive. T

here is no way to predict allele frequencies, given the information provided.

Q6. Mead and his colleagues proposed a hypothesis for the apparent heterozygote advantage for the PrP locus. What did they suggest as the basis for the high presence of both alleles?

History of cannibalism.

Protection from malaria.

Protection against plague.

They did not propose a heterozygotic advantage for the PrP locus.

Q7. A frog population has two alleles for skin color at the following relative frequencies: Allele SC1= 0.8, Allele SC2 = 0.2. Allele SC2 is:

Dominant

Recessive

Co-dominant

Impossible to determine dominance from the information given.

Q8. A bird population has two alleles for feather color at the following relative frequencies: Allele FC1 = 0.5, Allele FC2 = 0.5. Allele FC1 is:

Dominant

Recessive

Co-dominant

Impossible to determine dominance from the information given.

Q9. Use the following information for both questions 9 and 10: You encounter a few populations of millipedes with variation in skin color. Genotype can be inferred from coloration: CC millipedes are black, Cc millipedes are brown, and cc millipedes are yellow. [You can launch a calculator byclicking here.] If one millipede population has 60 black individuals, 20 brown individuals, and 20 yellow individuals, what is the relative frequency of allele C in that population?

0.5

0.6

0.7

0.8

Impossible to calculate from the information given.

Q10. If another millipede population's allele frequencies are 0.5 for C and 0.5 for c, what is the expected frequency of the cc genotype in the population, if the population is in Hardy-Weinberg equilibrium?

0.125

0.25

0.5

1.0

Impossible to calculate from the information given.

viridianlocust882

Need help with evolution questions:

1.) A haplotype is best defined as the ________________.

	haploid genotypes of all the gametes produced by a diploid individual

ABO blood type conferred by an individual gamete

genotype of either the paternal or maternal chromosomal complement

multilocus genotype of a chromosome or gamete

2.) Which of the following statements regarding linkage disequilibrium is true?

Exists when D is less than zero, but not when it is greater than zero.

Is reduced by sexual reproduction.

Is increased by crossing-over during meiosis.

Is increased by any random sampling error that happens to create or destroy certain chromosome genotypes but not others.

Is reduced by selection that favors certain combinations of genotypes.

3.) Selection on multilocus genotypes in random-mating populations leads to linkage disequilibrium when _______________.

it reduces mutation rates

it eliminates all haplotypes from the population

it prevents crossing-over during meiosis

some allele combinations confer greater fitness than do others

4.) When two loci are in linkage equilibrium, the allele carried on a chromosome at one locus is independent of the allele carried on the chromosome at another locus. When this is the case, _________________.

allele frequencies will not change over time

the two loci (or, more specifically, their protein products) do not interact

the frequency of each haplotype can be calculated by multiplying the frequency of its two alleles

all possible haplotypes occur at equal frequency

5.) Which of the following accurately characterize(s) Muller's ratchet model for the selective advantage of sexual reproduction?

Drift establishes linkage disequilibrium because multilocus genotypes with few mutations are eliminated by chance events.

In populations without sexual reproduction, deleterious mutations accumulate, eventually imposing such a burden that the population goes extinct.

Sex is favored selectively because it recreates the zero-mutation genotypes lost due to drift.

All of the above correctly characterize Muller's ratchet model for the evolution of sexual reproduction.

6.) The genetic signature of recent positive selection on a locus is _______________.

high frequency and low linkage disequilibrium

low frequency and low linkage disequilibrium

low frequency and high linkage disequilibrium

high frequency and high linkage disequilibrium

7.) Sexual reproduction is advantageous both in changing environments and in constant environments, compared to asexual reproduction.

True

False

8.) Sexual reproduction causes genetic recombination via crossing-over, which combines genotypes from different parents.

True

False

9.) One reason sex may be maintained in natural populations is proposed by the "Red Queen Hypothesis", which states that.....

genotypes created by sex are created by natural selection over and over

recombination creating novel genotypes that can resist infection by parasites

mutation load is reduced by novel adaptive mutations

the ability of sex to fix multiple

PCB 4674 Lecture Notes - Lecture 11: Allele Frequency, Genotype Frequency, Zygote

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