Part 3

A human sperm cell contains ______ copy (copies) of the SRY gene.

0 or 1

The frequency of two alleles in a gene pool is 0.19 (A) and 0.81(a). Assuming that the population is in Hardy-Weinberg equilibrium, what percentage of individuals in the population will be homozygous dominant (AA)?

0.04, or 4%

In garden peas, the allele T, which results in tall plants, has a frequency of 0.70, and the allele t, which results in dwarf plants, has a frequency of 0.30. In this population, what proportion of the plants are expected to be dwarf?

0.09

The frequency of two alleles in a gene pool is 0.19 (A) and 0.81(a). Assuming that the population is in Hardy-Weinberg equilibrium, what percentage of individuals in the population will be heterozygous (Aa)?

0.31, or 31%

Coloration in the peppered moth (shown here) is determined by a single gene with two alleles showing complete dominance. Dark moths are homozygous dominant or heterozygous for the gene, light moths are homozygous recessive. In a population of moths, you determine that 64 percent of the moths are dark. If the population is in Hardy-Weinberg equilibrium, the expected frequency of the dominant allele is

0.4

If a population with two alleles is at Hardy-Weinberg equilibrium and the frequency of one allele is 0.7, what is the heterozygote frequency?

0.42

Biologists genotyped a population sample of T. sirtalis garter snakes and found 17 homozygous wild-type snakes (D/D), 12 heterozygous (D/N) and 18 homozygous mutant snakes (N/N). Based on this information, calculate the allele frequencies, accurate to the second decimal point The frequency of the NaVD allele in the snake population was

0.49

The frequency of the NaVN allele in the snake population was

0.51

In a hypothetical population of tree swallows, 18 individuals are homozygous for the c4 allele, 22 individuals are heterozygous for the allele, and 10 individuals lack the allele. What is the frequency of the c4 allele?

0.58

In corn, kernel color is determined by two alleles of a single gene; the allele that results in white kernel color (W) is dominant to the allele that results in yellow kernel color (w). In a sample of 100 kernels from a population, there are 9 yellow kernels (ww) and 91 white kernels. Assuming that this population is in Hardy-Weinberg equilibrium, what are the frequencies of the two alleles of this gene?

0.70 W and 0.30 w

In a non-dividing somatic cell of a human male, there is (are) ______ copy (copies) of each gene on the X chromosome.

1

To determine the genotype of a tall pea plant, the tall plant can be crossed with a homozygous recessive dwarf plant. This is called a test cross. If the tall plant used in the test cross is heterozygous, what phenotypic ratio will be observed among the offspring?

1/2 tall and 1/2 dwarfed

If, instead of being allowed to self-fertilize, an F1 plant is crossed with a plant that has green seeds and white flowers, what proportion of the offspring will have yellow seeds and white flowers?

1/4

Consider two populations of beetles. In these beetles, body color is controlled by one gene with two alleles. The R allele determines red body (dominant), and the r allele determines brown body (recessive). In population A, 75% of the beetles are red; in population B 49% of the beetles are brown. Suppose that you find a third population of the same beetles, at a different location (C). You tally phenotypes and find out that 75% of beetles in this third population are red, just like in population A. What can you confidently say about this third population?

25% of beetles in population C have genotype rr.

If an F1 plant from this cross is allowed to self-fertilize, what proportion of the F2 offspring will have yellow seeds and white flowers?

3/16

Mendel crossed pure-breeding pea plants with purple flowers with pure-breeding pea plants with white flowers. Purple flowers are dominant to white flowers, and all F1 offspring all had purple flowers. If these F1 plants were allowed to self-fertilize, what phenotypic ratio would be expected in the F2 generation?

3/4 purple flowers and 1/4 white flowers

In a population that is at Hardy-Weinberg equilibrium, the highest possible frequency of heterozygotes for a locus with 2 alleles is

50%

Consider two populations of beetles. In these beetles, body color is controlled by one gene with two alleles. The R allele determines red body (dominant), and the r allele determines brown body (recessive). In population A, 75% of the beetles are red; in population B 49% of the beetles are brown. Assuming that both populations are in Hardy-Weinberg equilibrium, what are the frequencies of heterozygous beetles (Rr) in the two populations?

50% in population A; 42% in population B

In a population of Mendel's garden peas, the frequency of the dominant A (purple flower) allele is 80%. Let p represent the frequency of the A allele and q represent the frequency of the a allele. Assuming that the population is in Hardy-Weinberg equilibrium, what are the genotype frequencies?

64% AA, 32% Aa, 4% aa

The Punnett square below represents the expected outcome of a cross between RR and Rr

A RR homozygote and a Rr heterozygote

Duplication of a gene can occur as a result of

A chromosome-level mutation

An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?

A genetic bottleneck

What is a pure-breeding strain?

A strain that has shown the same traits for many generations

What is an evolutionary adaptation?

A trait that improves the fitness of its bearer, compared with individuals without the trait

What genotypic ratio will result from the test cross between a homozygous tall plant and a homozygous dwarf plant?

All Tt and no tt

In garden peas, yellow seed color is dominant to green seed color. This means that when a a true-breeding parent with yellow seeds is crossed with a true-breeding parent with green seeds,

All offspring will have yellow seeds.

If the tall plant used in the test cross is homozygous, what phenotypic ratio will be observed among the offspring of the test cross?

All tall and no dwarfed

Different species of fruit flies occupy each of the islands in the Hawaiian island chain, a group of volcanic islands that formed one after the other. One hypothesis for how the different fruit fly species formed is that, after each new island was formed, fruit flies from existing islands colonized it and subsequently diverged. If this hypothesis is correct, it would be an example of:

Allopatric speciation by dispersal

Two species of antelope ground squirrels are separated by the Grand Canyon. They are hypothesized to descend from a common ancestor, populations of which were separated as the canyon formed. If this hypothesis is correct, it would be an example of:

Allopatric speciation by vicariance

When a pure-breeding pea plant from a strain that produces round seeds is crossed with a pure-breeding plant from a strain that produces wrinkled seeds, all of the F1 progeny produce round seeds. Which of the following crosses will produce progeny in a 3/4 round : 1/4 wrinkled ratio?

An F1 plant is self-fertilized An F1 plant is crossed with another F1 plant

Every human egg cell contains

An X chromosome

Zebras and horses can mate with one another; their offspring are called zebroids. Zebroids, however, cannot produce offspring of their own. Based on this information, a biologist concludes that zebras and horses are different species. What species concept is being used?

Biological species concept

In humans, a female inherits her X chromosomes from

Both her mother and her father

How can you determine the genotype of a a tall pea plant?

By crossing it with a dwarf plant

How can evolutionary fitness be estimated?

Count the number of healthy, fertile offspring produced.

Small marine iguanas that live in the Galápagos Islands can sprint faster than large iguanas. Currently, the only predators of marine iguanas are hawks, which are able to catch iguanas regardless of their size. If new predators (for example, cats) that preferentially catch and eat slower iguanas are introduced to the island, iguana body size is likely to ________ in the absence of other factors; the iguanas would then be under ________ selection.

Decrease; Directional

Gene flow ______ genetic variation between populations.

Decreases

The T and t alleles are:

Different versions of the same gene

In general, sympatric speciation requires the action of _____ selection acting against hybrids.

Disruptive

Which of the following modes of selection operates when individuals at both extremes of the distribution have the highest fitness?

Disruptive selection

Which of the following statements about selection is true?

Disruptive selection favors individuals with extreme phenotypes.

In boa constrictors, sex is determined by the ZW system. Females are ZW, and males are ZZ. A female boa constrictor produces egg cells that carry

Either a Z chromosome or a W chromosome

Every human sperm cell contains

Either an X chromosome or a Y chromosome

When the conditions of the Hardy-Weinberg equilibrium are met in a population of organisms,

Evolution does not occur. Allele frequencies in the population do not change over time.

Which of the following statements are true?

Evolutionary change requires genetic variation. Populations evolve, not individuals. Some evolutionary mechanisms do not result in adaptations

Mendel crossed pea plants that were pure-breeding for purple flowers with pea plants that were pure-breeding for white flowers. The progeny of this cross always had purple flowers. The progeny are referred to as the

F1 generation

In pea plants, yellow seeds (G) are dominant to green seeds (g), and purple flowers (A) are dominant to white flowers (a). What is the genotype of a plant from a true-breeding strain that always produces yellow seeds and white flowers?

GGaa

A large rainstorm causes flooding and wipes out 87% of a small population of beetles. The remaining individuals have much lower genetic variation than the original population. Which of the following would explain the lack of H-W equilibrium seen after the flood?

Genetic drift

Which of the following can lead to genetic divergence between populations separated by geographic barriers?

Genetic drift Natural selection

A hypothetical endangered species of wildflower has been reduced to a single small population in a mountain meadow. A rare early spring blizzard kills all but 3 of the remaining plants, one of which has a rare mutation. This is an example of:

Genetic drift (bottleneck)

A true-breeding plant with green seeds and purple flowers is crossed with a true-breeding plant with yellow seeds and white flowers. What is the genotype of the plants in the F1 generation?

GgAa

A human male will pass on an X chromosome to

His daughters only

The mutant allele, NaVN, which confers resistance to TTX, is dominant to the wild-type allele, NaVD. Would you expect that, over time, the recessive wild-type allele would be completely eliminated from the population (assuming that garter snakes continued to eat TTX-producing newts)? Briefly explain your reasoning.

I would expect that if the snakes continue to eat the toxic newts they will continue to inherit the NaV^n mutant allele. The recessive NaV^D will not be completely eliminated from the population and still would be present in the population. While the allele could still be present in the heterozygous individuals and be expressed in the homozygous individuals.

Which of the following statements is/are true?

If in a population there are only two alleles at a certain locus, then their frequencies are related as follows: \ p = 1 - q Two populations can have the same allele frequencies but different genotype frequencies.

The rough-skinned newt, Taricha granulosa, is a common prey species for garter snakes, Thamnophis sirtalis. Several populations of newts in Oregon have individuals that can accumulate a nerve poison, tetrodotoxin (TTX) in their skin, which acts as an effective defense against garter snakes. The genetic basis of tetrodotoxin biosynthesis in newts is poorly understood, but its mechanism of action is known: the toxin binds to the Voltage-gated Na+ channel found on the membrane of nerve cells and blocks action potentials in nerves and muscles. Garter snakes that prey on newts become poisoned if they eat TTX-producing newts. However, resistance to TTX has evolved in some garter snake populations. The TTX-resistant phenotype in snakes is associated with mutations in the voltage-gated sodium channel (NaV) gene. One of these mutations, D1684N, prevents the toxin binding to the channel, resulting in a highly resistant, yet functional NaV channel protein. Which of these words or phrases best describes "resistance to TTX" in garter snakes?

It is an adaptation.

What does it mean when we say that the T allele is dominant to the t allele?

It means that a plant with the genotype Tt has the same phenotype as a plant with the genotype TT.

Which of the following processes can introduce a gene already present in one species into a second, different species?

Lateral gene transfer

The human karyotype with XY is a

Male

X-Linked Dominant Trait

Male and females are equally likely to be affected. All daughters of an affected father are affected, but no sons. Affected sons always have affected mothers. About 1/2 of the offspring of an affected mother will be infected. Affected daughters can have an affected mother or father. Traits does not skip generations.

To prevent self-fertilization of his pea plants, Mendel removed the _______ from the flowers that were pollinated.

Male reproductive organs

Autosomal Recessive Trait

Males and females are equally likely to be affected. Affected offspring often have unaffected parents. Unaffected parents of affected offspring are heterozygous (carriers). Affected offspring are homozygous. If both parents are heterozygous, about 1/4 of the offspring will be affected. Trait often skips generations.

Autosomal Dominant Trait

Males and females are equally likely to be affected. Affected offspring have at least one affected parents. Affected offspring are heterozygous if only one parent is affected. Unaffected offspring are homozygous recessive. If one parent is heterozygous, about 1/2 of the offspring will be affected. traits does not skip generations.

X-Linked Recessive Trait

Males are affected more frequently than females. Trait is never passed from father to son. Affected sons are usually born to carrier mothers. About 1/2 of the sons of a carrier mother will be affected. All daughters of an affected male and unaffected non-carrier female are carriers. Trait often skips generations.

During gametogenesis in a human male, the X and Y chromosomes segregate from one another during

Meiosis I

Two different alleles of the same gene will segregate from each other during

Meiosis I

The gene that determined height in Mendel's pea plants has been identified. This gene (T) encodes an enzyme called gibberellin 3-oxidase (GA 3-oxidase). The function of this enzyme is to convert an inactive plant compound into active gibberellin (shown below). Gibberellin is a plant hormone that stimulates growth, resulting in taller plants.

Missense mutation

If you were comparing the structures of fossils of extinct organisms, and had only fossil evidence available, which species concept(s) could you use to distinguish different species from one another?

Morphospecies concept

If asked how the ability to resist tetrodotoxin evolved in a snake population that initially did not have this ability, a biologist would infer that such evolution most likely occurred by

Natural selection

The process by which sympatric speciation might occur would most likely be the result of:

Natural selection

Which of the following evolutionary mechanisms always results in populations that are better adapted to their environments?

Natural selection

The only evolutionary process that leads to adaptive change is:

Natural selection.

Gus and Ida are two polar bears that live at the Central Park Zoo in New York City. They are first-generation zoo polar bears. They have lived at the zoo since 1985 and are completely separate from all other polar bears. Are they a different species based on the biological species concept?

No

The T allele codes for the functional GA 3-oxidase enzyme and is associated with the tall phenotype; the t allele codes for a non-functional version of this enzyme and is associated with the dwarfed phenotype. Which of the following genotypes will result in dwarfed plants?

Only tt

One of the characteristics that Mendel studied was plant height, which may be tall or dwarfed.

Phenotype

Consider two populations of beetles. In these beetles, body color is controlled by one gene with two alleles. The R allele determines red body (dominant), and the r allele determines brown body (recessive). In population A, 75% of the beetles are red; in population B 49% of the beetles are brown. Assuming both populations are in Hardy-Weinberg equilibrium, which population has a greater frequency of the R allele?

Population A

You observe two birds mating that you do not believe to belong to the same species. The eggs from this breeding do not hatch, and when you obtain one of the eggs, you find embryonic development stopped not long after fertilization. Which of the following conclusions is supported by these observations?

Postzygotic factors prevented successful reproduction.

In the ocean, many species of sea urchins live in the same habitat and release gametes simultaneously. Gametes of species A are unable to fuse with gametes of species B. What type of reproductive isolation is this?

Prezygotic; gametic barrier

Which of the following is a possible genotype for a gamete produced by an organism with genotype Rr?

R and r

Which of the following observations would pose the greatest challenge to applicationof the morphospecies concept?

Sexual dimorphism

Which of the following modes of selection leads to a reduction in phenotypic variation in a population but no change in the mean?

Stabilizing selection

The X and Y chromosomes

Synapse with each other during meiosis.

In a pea plant that is heterozygous for T and t, which of the following statements about meiosis is correct?

T and t segregate from one another during meiosis I, when homologous chromosomes separate.

Despite inhabiting overlapping ranges, the western spotted skunk and the eastern spotted skunk do not interbreed, partly because the western species breeds in early fall and the eastern species breeds in late winter to early spring. This is an example of

Temporal isolation

Which of the following statements are true about a gene with two alleles in a population that is in Hardy-Weinberg equilibrium?

The frequencies of the two alleles will remain constant over time.

Which of the following big sagebrush plants has highest fitness, based only on the information presented?

The individual that produces 3% more viable seeds each year than others in its population.

Saying that a population is in Hardy-Weinberg equilibrium for a certain locus means that:

The observed genotype frequencies in the population are equal to the expected (p2, 2pq, and q2)

If the ancestors of Mendel's pea plants all carried the T allele, which encodes a functional GA 3-oxidase enzyme, which of the following statements best explains how the t allele first appeared in the population?

The t allele first appeared due to an error in replication.

Mendel crossed pea plants that were pure-breeding for tall height with pea plants that were pure-breeding for dwarf height. The progeny of this cross were always tall. This led him to conclude that

The tall phenotype is dominant

A monohybrid cross is a cross that involves a single

Trait

In pea plants, flowers may be purple or white. Flower color is an example of a ______, and purple and white are examples of ______.

Trait; Phenotypes

What is the phenotype of the plants in the F1 generation of the cross described in the previous question?

Yellow seeds and purple flowers

Can a heterozygous (Tt) pea plant produce the active gibberellin molecule?

Yes

A true-breeding parent plant with green seeds and purple flowers will produce gametes with the genotype(s):

gA

In pea plants, yellow seeds (G) are dominant to green seeds (g), and purple flowers (A) are dominant to white flowers (a). What is the genotype of a plant from a true-breeding strain that always produces green seeds and purple flowers?

ggAA