Biology 1001A Study Guide - Midterm Guide: Nectar, Symplesiomorphy, Species Problem

Part A

In humans, individuals may or may not have a widow’s peak. This trait is controlled by genes at a single locus, with the allele for having a widow’s peak dominant to the allele for not having one. A population of humans is sampled; 59 have a widow’s peak and 44 do not. 25 of the people with a widow’s peak are homozygous dominant. What are the frequencies of the dominant and recessive alleles observed in this sample?

p = _____

q = _____

Part B

In a species of corn, individuals have either narrow or wide corn cobs. This trait is controlled by genes at a single locus, with the narrow cob allele dominant to the wide cob allele. A farmer counts 74 narrow cob and 113 wide cob plants in a field. Of the narrow cob plants, 28 are homozygous dominant. What are the frequencies of the dominant and recessive alleles observed in this sample?

p = _____

q = _____

Part C

In a population of peas, the frequency of the dominant allele for a purple flower is 0.61 and the frequency of the recessive allele for a white flower is 0.39. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 500 peas?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Part D

In mice, a mahogany coat color allele is dominant over the tan coat color allele. In a population of mice, the frequency of the allele for mahogany coat color is 0.19 and the frequency of the allele for tan coat color is 0.81. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 100 mice?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Part E

In humans, the free earlobe allele is dominant over the attached ear lobe allele. In a population of humans, the frequency of the allele for free earlobes is 0.42 and the frequency of the allele for attached earlobes is 0.58. What would the genotypic frequencies be if the population is in equilibrium?

_____ = Frequency of homozygous dominant individuals

_____ = Frequency of heterozygous individuals

_____ = Frequency of homozygous recessive individuals

How many individuals would you expect of each genotype in a population of 25 humans?

_____ = Number of homozygous dominant individuals

_____ = Number of heterozygous individuals

_____ = Number of homozygous recessive individuals

Consider a single locus with three alleles: A₁, A₂, and A₃.

1) Write down all of the diploid genotypes possible at this locus.

2) Derive the equation for the frequency of allele A₁ as a function of the genotype frequencies.

Consider the following two datasets:

At the M locus:

In a study of 1000 adults, the following genotype numbers were found:

M₁M₁ - 213 individuals

M₁M₂ - 489 individuals

M₂M₂ - 298 individuals

At the S locus:

In a study of 4555 adults, the following genotype numbers were found:

S₁S₁ - 3564 individuals

S₁S₂ - 979 individuals

S₂S₂ - 12 individuals

Assignment: For both loci

Calculate the frequency of the alleles.

Calculate expected number of each genotype if the population were in Hardy-Weinberg equilibrium.

Identify which locus most clearly violates at least one of the H-W assumptions

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.