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block

The chromosome theory of inheritance states that _____.

Select the correct answer(s).  

(0/0)

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A. genes occupy specific positions on chromosomes

A and B are correct.

B. homologous chromosomes segregate from each other during meiosis

A, B, and C are correct.

C. chromosomes assort independently during meiosis

none

Why did Morgan choose Drosophilafor his genetics experiments?

Select the correct answer(s).  

(0/0)

---

Both B and D are correct.

C. They have a large number of chromosomes.

D. Drosophila chromosomes can be easily distinguishable under a light microscope.

A. They have a long generation time.

B. A single mating can produce many offspring.

none

With a microscope, you examine some somatic cells from a woman and notice that each nucleus has two Barr bodies. What can you infer about the sex chromosomes in this individual?

Select the correct answer(s).  

(0/0)

---

She is XXY, but the Y chromosome lacks the SRY gene.

She is XXXX.

She is XXX.

She is XX.

None of the listed responses are correct.

none

A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way: A woman with this defect typically has small patches of skin with sweat glands and other patches without sweat glands. In women, the pattern of sweat-gland distribution can best be explained by _____.

Select the correct answer(s).  

(0/0)

---

an operon

a mutation

RNA splicing

X chromosome inactivation

a homeobox

none

In a certain fish, fin rays (supporting structures for the fins) can be either bony or soft in adult fish. Sex linkage in a fish is similar to that in humans. What evidence would most strongly support the idea that the ray locus is on the X chromosome?

Select the correct answer(s).  

(0/0)

---

Females with either bony or soft rays can reproduce, but males with soft rays cannot transfer sperm to the female.

Bony ray males can pass on bony rays only to their male offspring.

Females with bony rays cannot pass bony rays to female offspring even if they are mating with a bony ray male.

All of the listed responses are correct.

Matings of soft ray males and bony ray females give different results from the matings of bony ray males and soft ray females.

none

Which of the following results of Thomas Hunt Morgan's experiments with white-eyed mutant flies was unexpected in light of Mendelian genetics?

Select the correct answer(s).  

(0/0)

---

In the parental cross, a white-eyed male was crossed with a red-eyed female. The F1 progeny all had red eyes.

All listed answers are correct.

The mutant allele (white eyes) was recessive.

Among the F2 progeny, only males had white eyes. All of the females had red eyes.

The F1 flies were crossed with each other, and the F2 progeny included red-eyed and white-eyed flies in a 3:1 ratio.

none

X-linked genes differ from Y-linked genes in which of the following ways?

Select the correct answer(s).  

(0/0)

---

Though most X-linked genes determine sex, Y-linked genes control for characters unrelated to sex.

Only X-linked genes are technically sex-linked because Y-linked genes affect characteristics unrelated to sex.

Sons and daughters can inherit alleles of X-linked genes from fathers proportionally but only sons inherit alleles of Y-linked genes from their fathers.

Sons and daughters have equal probabilities in inheriting a recessive allele of an X-linked gene from their mother, but only sons can inherit rare Y-linked genetic disorders from their father.

Although the X and Y chromosomes carry genes that determine sexual characteristics, there are not corresponding regions of homology for genes located on each chromosome.

none

Wild type refers to _____.

Select the correct answer(s).  

(0/0)

---

the most extreme mutant phenotype observed in an experiment

a kind of chromosomal deletion

extranuclear genes

any mutant genotype

the most common phenotype thought to be found in the natural population

none

A woman is red-green color-blind. What can we conclude, if anything, about her father?

Select the correct answer(s).  

(0/0)

---

He is red-green color-blind.

We have too little information to tell.

none of the above

There is a 50% probability that he has normal vision.

He has two Y chromosomes.

none

In an X-linked, or sex-linked, trait, it is the contribution of _____ that determines whether a son will display the trait.

Select the correct answer(s).  

(0/0)

---

the paternal grandmother

the father

the paternal grandfather

none of the above

the mother

none

In werewolves (hypothetically), pointy ears (P) are dominant over round ears (p). The gene is on the X chromosome. (Sex determination in werewolves is the same as for "other" humans.) A certain female werewolf has pointy ears even though her father had round ears. What percentage of her sons will have round ears if she mates with a werewolf with round ears?

Select the correct answer(s).  

(0/0)

---

0%

25%

0.5

75%

100%

none

Hemophilia is a sex-linked disorder. The daughter of a father with hemophilia and a carrier mother has a _____ probability of having hemophilia.

Select the correct answer(s).  

(0/0)

---

25%

0.5

100%

0%

33%

none

Duchenne muscular dystrophy is caused by a sex-linked recessive allele. Its victims are almost invariably boys, who usually die before the age of 20. Why is this disorder almost never seen in girls?

Select the correct answer(s).  

(0/0)

---

The allele is carried on the Y chromosome.

Sex-linked traits are never seen in girls.

To express an X-linked recessive allele, a female must have two copies of the allele.

A sex-linked allele cannot be passed from mother to daughter.

Nondisjunction occurs in males but not in females.

none

Queen Victoria was a carrier of a recessive sex-linked allele for hemophilia. Which of the following possibilities could explain the presence of the hemophilia allele in her genotype?

Select the correct answer(s).  

(0/0)

---

Either her mother was a carrier or her father had a dominant allele.

Both her mother and her father had hemophilia.

Either her mother was a carrier or her father had hemophilia.

Either her mother was homozygous dominant or her father had hemophilia.

none of the above

none

If a mother is heterozygous for a recessive sex-linked trait and her husband has the dominant allele, which one of the following is true about the probabilities for their children?

Select the correct answer(s).  

(0/0)

---

none of the above

Half of their sons will have the recessive trait.

All of their sons will have the recessive trait.

None of their sons will have the recessive trait.

All of their daughters will be heterozygous.