Deck 22: Population and Evolutionary Genetics

Question 1

Assume that in a Hardy -Weinberg population, 9 percent of the individuals are of the homozygous recessive phenotype. What percentage are homozygous dominant?

Answer 1

49 percent

Question 2

Assume that a trait is caused by the homozygous state of a gene that is recessive and autosomal. Nine percent of the individuals in a given population express the
phenotype caused by this gene. What percentage of the individuals would be heterozygous for the gene? Assume that the population is in Hardy -Weinberg equilibrium.

Answer 2

42 percent

Question 3

A number of mechanisms operate to maintain genetic diversity in a population. Why is such diversity favored?

A) Homozygosity is an evolutionary advantage.
B) Diversity leads to inbreeding advantages.
C) Genetic diversity may better adapt a population to inevitable changes in the environment.
D) Genetic diversity helps populations avoid diploidy.
E) Greater genetic diversity increases the chances of haploidy.

Answer 3

C

Question 4

Which general term is used to group various biological and behavioral properties of organisms that act to prevent or reduce interbreeding?

A) genetic divergence
B) phyletic evolution
C) reproductive isolating mechanisms
D) allopatric speciation
E) inbreeding

Question 5

List and briefly describe three factors that contribute to the phenomenon of natural selection.

Question 6

List at least five of the assumptions that pertain to a population in a Hardy -Weinberg equilibrium.

Question 7

Assuming that p = 0.3 for a population in Hardy -Weinberg equilibrium, what would be the expected frequency of heterozygotes for the involved allelic pair?

Question 8

What does the variable 2pq represent?

Question 9

In a population of 100 individuals, 49 percent are of the NN blood type. What percentage is expected to be MN assuming Hardy -Weinberg equilibrium conditions?

A) 51 percent
B) 42 percent
C) 9 percent
D) 21 percent
E) There is insufficient information to answer this question.

Question 10

In small isolated populations, gene frequencies can fluctuate considerably. The term that applies to this circumstance is _.

A) stabilizing selection
B) natural selection
C) allelic separation
D) genetic drift
E) genetic isolation

Question 11

Which method is often used to analyze proteins and nucleic acids by physical separation when estimating genetic variation in populations?

A) in situ hybridization
B) electrophoresis
C) centrifugation
D) fluorometry
E) absorption spectrophotometry

Question 12

When all genotypes within a population do not have equal rates of survival, then allele
frequencies may change from one generation to the next by a process called

Question 13

Which term is given to the total genetic information carried by all members of a population?

A) gene pool
B) breeding unit
C) race
D) genome
E) chromosome complement

Question 14

________ is a group of individuals belonging to the same species that live in a defined geographic area and actually or potentially interbreed.

A) Hybrid
B) Pod
C) Pool
D) Population
E) Cohort

Question 15

Briefly define the term genetic equilibrium.

Question 16

In a population that meets the Hardy -Weinberg equilibrium assumptions, 81 percent of the individuals are homozygous for a recessive allele. What percentage of the
individuals would be expected to be heterozygous for this locus in the next generation?

Question 17

In a population of 10,000 individuals, in which 3600 are MM, 1600 are NN, and 4800 are MN, what are the frequencies of the M alleles and the N alleles?

Question 18

What is meant by the equation p + q = 1.0?

Question 19

A certain form of albinism in humans is recessive and autosomal. Assume that 1 percent of the individuals in a given population are albino. Assuming that the
population is in Hardy -Weinberg equilibrium, what percentage of the individuals in this population are expected to be heterozygous?

Question 20

In a population of cattle, the following color distribution was noted: 36 percent red (RR), 48 percent roan (Rr), and 16 percent white (rr). Is this population in a
Hardy -Weinberg equilibrium? What will be the distribution of genotypes in the next generation if the Hardy -Weinberg assumptions are met?

Question 21

Mutation and migration introduce new alleles into populations. What is the most likely principal force that will shift allelic frequencies within large populations?

Question 22

Define the term fitness and relate it to the meaning of selection coefficient.

Question 23

What are phylogenetic trees?

Question 24

Contrast directional and stabilizing forms of selection.

Question 25

Would one expect a linear relationship between DNA sequence divergence and phylogenetic distance? Why or why not?

Question 26

What are the genetic consequences of inbreeding?

Question 27

One of the Hardy -Weinberg assumptions states that all genotypes in the population are free of selective advantage. What influence might a selective advantage of a
genotype have on a Hardy -Weinberg equilibrium?

Question 28

Why might mitochondrial DNA be used in construction of phylogenetic trees rather than nuclear DNA?

Question 29

Which term is given to the measure of the proportion of offspring that a particular phenotype will contribute to the next generation?

Question 30

Present a rationale for using DNA sequence polymorphisms as an index of genetic diversity. Is genetic diversity directly proportional to evolutionary (phylogenetic) diversity?

Question 31

Which would change allele frequencies more quickly: selection against a dominant allele or selection against a recessive allele?

Question 32

Suppose that a given gene undergoes a mutation to a dominant allele such that 2 out of 100,000 offspring exhibit the new mutant phenotype. Assuming that these offspring are heterozygous, what is the mutation rate for the gene?

Question 33

In zoo animals, inbreeding often occurs because of a lack of a sufficient pool of
breeding individuals. Under such conditions, which two characteristics are often exhibited among inbred organisms?

Question 34

Define the term speciation.

Question 35

One of the Hardy -Weinberg assumptions states that the population is infinitely large. What influence might a small population size have on a Hardy -Weinberg equilibrium?

Question 36

Which single event is probably common to all occurrences of speciation?

Question 37

What is the original source of genetic variation in a population? Which natural factors affect changes in this original variation?

Question 38

The difference between fitness of a given genotype and another genotype considered optimal is called the selection coefficient (s). What is the selection coefficient for a
genotype (aa) that produces an average of 99 offspring when Aa individuals produce an average of 100 offspring?

Question 39

Migration occurs when individuals move between populations. Considering a single pair of alleles, A and a, which formula is used to indicate the new frequency of A in one generation of migration?

Question 40

Why are some proteins more likely than others to diverge within a species?

Question 41

Evolution is dependent on genetic diversity in the evolving population.

Question 42

Selection is the differential reproduction of genotypes, resulting from their variable fitness.

Question 43

Mutations are regarded as a strong evolutionary mechanism for changing allelic frequencies.

Question 44

In large random mating populations, random genetic drift is usually a significant factor in changing gene frequencies.

Question 45

Inbreeding by itself can change gene frequencies.

Question 46

In directional selection, both phenotypic extremes are equally selected against.

Question 47

In the case of complete dominance in a population in equilibrium, we cannot tell which individuals are homozygous dominants and which are heterozygous, but by knowing
the frequency of the homozygous recessives, we can estimate the frequency of homozygous dominant and heterozygous genotypes.

Question 48

In an evolutionary sense, what is meant by the term molecular clock?

Question 49

Given an inheritance pattern of incomplete dominance and 81 flowers that are red (R1R1), 18 flowers that are pink (R1R2), and 1 flower that is white (R2R2), the frequency of the R1 allele is 0.9.

Question 50

Genetic drift is primarily associated with relatively small breeding populations.

Question 51

For a given locus, in a population with two alternative alleles, the allele frequencies p + q = 1.0.

Question 52

If a gene has three alleles in a population, their frequencies must add up to 1.5.

Question 53

Natural selection occurs when there is nonrandom elimination of genotypes from a population due to differences in viability or reproductive success.