Population geneticists study changes in the nature and amount of genetic variation in populations, the distribution of different genotypes, and how forces such as selection and drift act on genetic variation to bring about evolutionary change in populations and the formation of new species. From the explanation given in the chapter, what answers would you propose to the following fundamental questions?

How do we know how much genetic variation is in a population?

Population geneticists study changes in the nature and amount of genetic variation in populations, the distribution of different genotypes, and how forces such as selection and drift act on genetic variation to bring about evolutionary change in populations and the formation of new species. From the explanation given in the chapter, what answers would you propose to the following fundamental questions?

How do geneticists detect the presence of genetic variation as different alleles in a population?

Population geneticists study changes in the nature and amount of genetic variation in populations, the distribution of different genotypes, and how forces such as selection and drift act on genetic variation to bring about evolutionary change in populations and the formation of new species. From the explanation given in the chapter, what answers would you propose to the following fundamental questions?

How do we know whether the genetic structure of a population is static or dynamic?

Population geneticists study changes in the nature and amount of genetic variation in populations, the distribution of different genotypes, and how forces such as selection and drift act on genetic variation to bring about evolutionary change in populations and the formation of new species. From the explanation given in the chapter, what answers would you propose to the following fundamental questions?

How do we know when populations have diverged to the point that they form two different species?

Population geneticists study changes in the nature and amount of genetic variation in populations, the distribution of different genotypes, and how forces such as selection and drift act on genetic variation to bring about evolutionary change in populations and the formation of new species. From the explanation given in the chapter, what answers would you propose to the following fundamental questions?

How do we know the age of the last common ancestor shared by two species?

Write a short essay describing the roles of mutation, migration, and selection in bringing about speciation.

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:

0.0064

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:

0.000081

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:

0.09

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:

0.01

Consider rare disorders in a population caused by an autosomal recessive mutation. From the frequencies of the disorder in the population given, calculate the percentage of heterozygous carriers:

0.10

What must be assumed in order to validate the answers in Problem 7?

In a population where only the total number of individuals with the dominant phenotype is known, how can you calculate the percentage of carriers and homozygous recessives?

If 4 percent of a population in equilibrium expresses a recessive trait, what is the probability that the offspring of two individuals who do not express the trait will express it?

Consider a population in which the frequency of allele A is p=0.7 and the frequency of allele a is q=0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

wAA=1, wAa=0.9, waa=0.8

Consider a population in which the frequency of allele A is p=0.7 and the frequency of allele a is q=0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

wAA=1, wAa=0.95, waa=0.9

Consider a population in which the frequency of allele A is p=0.7 and the frequency of allele a is q=0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

wAA=1, wAa=0.99, waa=0.98

Consider a population in which the frequency of allele A is p=0.7 and the frequency of allele a is q=0.3 and where the alleles are codominant. What will be the allele frequencies after one generation if the following occurs?

wAA=0.8, wAa=1, waa=0.8

If the initial allele frequencies are p = 0.5 and q = 0.5 and allele a is a lethal recessive, what will be the frequencies after 1, 5, 10, 25, 100, and 1000 generations?

Under what circumstances might a lethal dominant allele persist in a population?

Assume that a recessive autosomal disorder occurs in 1 of 10,000 individuals (0.0001) in the general population and that in this population about 2 percent (0.02) of the individuals are carriers for the disorder. Estimate the probability of this disorder occurring in the offspring of a marriage between first cousins. Compare this probability to the population at large.

One of the first Mendelian traits identified in humans was a dominant condition known as brachydactyly. This gene causes an abnormal shortening of the fingers or toes (or both). At the time, some researchers thought that the dominant trait would spread until 75 percent of the population would be affected (because the phenotypic ratio of dominant to recessive is 3 : 1). Show that the reasoning was incorrect.

Describe how populations with substantial genetic differences can form. What is the role of natural selection?

Achondroplasia is a dominant trait that causes a characteristic form of dwarfism. In a survey of 50,000 births, five infants with achondroplasia were identified. Three of the affected infants had affected parents, while two had normal parents. Calculate the mutation rate for achondroplasia and express the rate as the number of mutant genes per given number of gametes.

A recent study examining the mutation rates of 5669 mammalian genes (17,208 sequences) indicates that, contrary to popular belief, mutation rates among lineages with vastly different generation lengths and physiological attributes are remarkably constant [Kumar, S., and Subramanian, S. (2002). Proc. Natl. Acad. Sci. USA 99:803–808]. The average rate is estimated at 12.2×10⁻⁹ per bp per year. What is the significance of this finding in terms of mammalian evolution?

What are considered significant factors in maintaining the surprisingly high levels of genetic variation in natural populations?

A botanist studying water lilies in an isolated pond observed three leaf shapes in the population: round, arrowhead, and scalloped. Marker analysis of DNA from 125 individuals showed the round-leaf plants to be homozygous for allele r1, while the plants with arrowhead leaves were homozygous for a different allele at the same locus, r2. Plants with scalloped leaves showed DNA profiles with both the r1 and r2 alleles. Frequency of the r1 allele was estimated at 0.81. If the botanist counted 20 plants with scalloped leaves in the pond, what is the inbreeding coefficient F for this population?

A farmer plants transgenic Bt corn that is genetically modified to produce its own insecticide. Of the corn borer larvae feeding on these Bt crop plants, only 10 percent survive unless they have at least one copy of the dominant resistance allele B that confers resistance to the Bt insecticide. When the farmer first plants Bt corn, the frequency of the B resistance allele in the corn borer population is 0.02. What will be the frequency of the resistance allele after one generation of corn borers have fed on Bt corn?

In an isolated population of 50 desert bighorn sheep, a mutant recessive allele c when homozygous causes curled coats in both males and females. The normal dominant allele C produces straight coats. A biologist studying these sheep counts four with curled coats. She also takes blood samples from the population for DNA analysis, which reveals that 17 of the sheep are heterozygous carriers of the c allele. What is the inbreeding coefficient F for this population?

To increase genetic diversity in the bighorn sheep population described in Problem 23, ten sheep are introduced from a population where the c allele is absent. Assuming that random mating occurs between the original and the introduced sheep, and that the c allele is selectively neutral, what will be the frequency of c in the next generation?