Chapter 12: Chromosomal Basis of Inheritance

What can we observe in order to visualize Mendel's Law of Segregation?

-sister chromatids separating during mitosis

-the replication of DNA

-the behavior of sex-linked genes

-homologous chromosomes separating during meiosis II

-homologous chromosomes separating during meiosis I

homologous chromosomes separating during meiosis I

What name is given to the most common phenotype in a natural population?

wild type

locus

genotype

mutant phenotype

autosome

wild type

A white-eyed female Drosophila is crossed with a red-eyed male Drosophila. Which statement below correctly describes the results?

-None of the females will have red eyes.

-Fifty percent of the females will have red eyes.

-Twenty-five percent of the females will have white eyes.

-Twenty-five percent of the females will have red eyes.

-None of the females will have white eyes.

None of the females will have white eyes

In humans, what determines the sex of offspring, and why?

-The male determines sex because the sperm can fertilize either a female egg or a male egg.

-The female gamete determines sex because only the female gamete provides cytoplasm to the zygote.

-The chromosome contribution from both parents determines sex because the offspring uses all the parents' chromosomes.

-The female gamete determines sex because only the female gametes can have one of two functional sex chromosomes.

-The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome.

The male gamete determines sex because each male gamete can contribute either an X or a Y chromosome

Which of the following is true of an X-linked gene but not of a Y-linked gene?

-The gene is present in both males and females.

-It is expressed in half of the cells of either males or females.

-Sister chromatids separate during mitosis.

-It does not segregate like other genes.

-It is only expressed in female offspring.

The gene is present in both males and females

Males are more often affected by sex-linked traits than females because

-female hormones such as estrogen often compensate for the effects of mutations on the X chromosome.

-X chromosomes in males generally have more mutations than X chromosomes in females.

-male hormones such as testosterone often alter the effects of mutations on the X chromosome.

-mutations on the Y chromosome often worsen the effects of X-linked mutations.

-males are hemizygous for the X chromosome.

males are hemizygous for the X chromosome

In cats, black fur color is caused by an X-linked allele; the other allele at this locus causes orange color. The heterozygote is tortoiseshell. What kinds of offspring would you expect from the cross of a black female and an orange male?

-tortoiseshell females; black males

-black females; orange males

-orange females; orange males

-tortoiseshell females; tortoiseshell males

-orange females; black males

tortoiseshell females; black males

A man who is an achondroplastic dwarf with normal vision marries a color-blind woman of normal height. The man's father was 6 feet tall, and both the woman's parents were of average height. Achondroplastic dwarfism is autosomal dominant, and red-green color blindness is X-linked recessive.

How many of their daughters might be expected to be color-blind dwarfs?

one out of four

all

none

half

three out of four

none

In general, the frequency with which crossing over occurs between two linked genes depends on __________.

-the characters the genes code for

-whether the genes are on the X or some other chromosome

-how far apart they are on the chromosome

-whether the genes are dominant or recessive

-the phase of meiosis in which the crossing over occurs

how far apart they are on the chromosome

What does a frequency of recombination of 50% indicate?

-The genes are located on sex chromosomes.

-All of the offspring have combinations of traits that match one of the two parents.

-Independent assortment is hindered.

-The two genes are likely to be located on different chromosomes.

The two genes are likelu to be located on different chromosomes

What does a frequency of recombination of 50% indicate?

-The genes are located on sex chromosomes.

-All of the offspring have combinations of traits that match one of the two parents.

-Independent assortment is hindered.

-The two genes are likely to be located on different chromosomes.

The two genes are likely to be located on different chromosomes

Why does recombination between linked genes continue to occur?

-Recombination is a requirement for independent assortment.

-Recombination must occur or genes will not assort independently.

-New allele combinations are acted upon by natural selection.

-Without recombination there would be an insufficient number of gametes.

New allele combinations are acted upon by natural selection

If cell X enters meiosis, and nondisjunction of one chromosome occurs in one of its daughter cells during meiosis II, what will be the result at the completion of meiosis?

-Half of the gametes descended from cell X will be n + 1, and half will be n - 1.

-Two of the four gametes descended from cell X will be haploid, and two will be diploid.

-There will be three extra gametes.

-One-fourth of the gametes descended from cell X will be n + 1, 1/4 will be n - 1, and 1/2 will be n.

-All the gametes descended from cell X will be diploid.

One fourth of the gametes descended from cell X will be n+1, 1/4 will be n-1, and 1/2 will be n

What is a nondisjunction?

-An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

-An error in which a diploid cell or organism lacks a chromosome of one type, producing a chromosome number of 2n - 1

-An error in which a diploid cell or organism has an extra chromosome of one type, producing a chromosome number of 2n + 1

-None of the above

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

When can nondisjunction occur? Choose the best answer.

-In meiosis, when homologous chromosomes fail to separate

-In mitosis, when sister chromatids fail to separate

-In meiosis, when sister chromatids fail to separate

-All three answers are correct.

All three answers are correct

Which syndrome is characterized by the XO chromosome abnormality?

Turner syndrome

Trisomy X

Down syndrome

Klinefelter syndrome

Turner syndrome

What kind of cell results when a diploid and a haploid gamete fuse during fertilization?

A monosomic cell

A triploid cell

A monoploid cell

A trisomic cell

A triploid cell

Of the following chromosomal abnormalities, which type is most likely to be viable in humans?

Monosomy

Trisomy

Triploidy

Haploidy

Trisomy

If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?

-A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.

-No error occurred; these are normal gametes.

-A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

-A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell.

A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell

If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?

-No error occurred; these are normal gametes.

-A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.

-A nondisjunction error occurred in meiosis I, in which both members of all homologous pairs migrated to the same pole of the cell.

-A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell

Which of the following results in a situation in which the chromosome number is either 2n+1 or 2n-1?

gene linkage

polyploidy

aneuploidy

methylation

inversion

aneuploidy

What results if a fragment of a chromosome breaks off and then reattaches to the original chromosome at the same place but in the reverse direction?

polyploidy

an inversion

a translocation

a deletion

a nondisjunction

an inversion

All but one of the following diseases/disorders is the result of chromosomal alterations.

Mosaicism

Turner syndrome

Chronic myelogenous leukemia (CML)

Down syndrome (Trisomy 21)

Cri du chat syndrome

Mosaicism

A translocation causes which of the following results?

-exchange of homologous chromosome fragments

-nondisjunction

-exchange of nonhomologous chromosome fragments

-deletion only

exchange of nonhomologous chromosome fragments

Of the following human aneuploidies, which is the one that generally has the most severe impact on the health of the individual?

45, X

47, XXY

47, XXX

47, XYY

47, +21

47, +21

What is the source of the extra chromosome 21 in an individual with Down syndrome?

-nondisjunction in the father only

-nondisjunction or translocation in either parent

-duplication of the chromosome

-nondisjunction in the mother only

nondisjunction or translocation in either parent

A woman is found to have 47 chromosomes, including three X chromosomes. Which of the following describes her expected phenotype?

-sterile female

-masculine characteristics such as facial hair

-healthy female of slightly above-average height

-enlarged genital structures

healthy female of slightly above-average height

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of segregation?

-The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

-Sister chromatids separate during anaphase II.

-The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

The two alleles for each gene separate as homologous chromosomes move apart during anaphase I

Which of these descriptions of the behavior of chromosomes during meiosis explains Mendel's law of independent assortment?

-Sister chromatids separate during anaphase II.

-The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs.

-The two alleles for each gene separate as homologous chromosomes move apart during anaphase I.

The arrangement of each pair of homologous chromosomes on the metaphase plate during metaphase I is random with respect to the arrangements of other pairs

Select the correct statement(s) about sex determination in animals.

-In all animals, males are XY and females are XX.

-In all animals, males have the SRY gene and females lack this gene.

-The mechanism of sex determination varies with different animal species.

The mechanism of sex determination varies with different animal species

Imagine a human disorder that is inherited as a dominant, X-linked trait. How would the frequency of this disorder vary between males and females?

-Females would display this disorder with greater frequency than males.

-Males and females would display this disorder with equal frequency.

-Males would display this disorder with greater frequency than females.

Females would display this disorder with greater frequency than males

Gregor Mendel set up a dihybrid cross with one pea plant from the parental generation (P) producing round yellow peas and the other pea plant producing wrinkled green peas. The F2 generation included 315 plants producing round yellow peas, 108 with round green peas, 101 with wrinkled yellow peas, and 32 with wrinkled green peas. How would these results have differed if pea shape and pea color had been linked genes, located close together on the same chromosome?

-The F2 generation would have included a higher percentage of pea plants producing yellow peas.

-The F2 generation would have included a higher percentage of pea plants producing round, yellow peas.

-The F2 generation would have included a lower percentage of pea plants producing wrinkled, green peas.

The F2 generation would have included a higher percentage of pea plants producing round, yellow peas