Chapter 9

How many pairs of autosomes do humans have?

22

If a human somatic cell is in metaphase, it has __________ chromatids.

92

Pea plants are tall if they have the genotype TT or Tt, and they are short if they have genotype tt. A tall plant is mated with a short plant. Which outcome below would indicate that the tall parent plant was heterozygous?

A 1:1 ratio of tall offspring to short offspring

Homologous chromosomes move toward opposite poles of a dividing cell during __________.

Meiosis I

Which of the following represents a mismatch or incorrect description?

Metaphase: the nuclear envelope disappears

In a human skin cell that is going through the cell cycle, when do the centrosomes separate?

Prophase

Synapsis occurs during __________.

Prophase I

Which of the following human diseases is inherited as a simple recessive trait?

Cystic fibrosis

Which of the following occurs during anaphase II?

Sister chromatids separate and migrate toward opposite poles.

A human cell containing 22 autosomes and a Y chromosome is a __________.

Sperm

A karyotype is a __________.

photograph of all of an individual's chromosomes

Tail length in a certain species of armadillo falls along a continuum, following a normal distribution. Assuming that environmental factors do not play an important role in determining tail length, this type of variation probably reflects __________.

polygenic inheritance

Crossing over occurs during __________.

prophase I

In Mendel's monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation had the __________ phenotype because their genotype was __________ at the flower-color locus.

purple-flowered; heterozygous

One event occurring during prophase is __________.

the beginning of the formation of a mitotic spindle

In a certain plant, the alleles A, B, and C are completely dominant to the alleles a, b, and c. A plant with the genotype AABbcc will have the same phenotype as a plant with the genotype __________.

AaBBcc

Fertilization produces a __________.

Diploid zygote

Which of the following does not occur during mitosis?

Duplication of chromosomes

When two average-height parents give birth to a child exhibiting achondroplasia, it is most likely due to a new mutation. This is because __________.

achondroplasia is caused by an allele that is always expressed; therefore, the parents must not have the allele

According to Mendel's law of segregation, __________.

allele pairs separate in gamete formation

The function of mitosis and cytokinesis is to produce daughter cells that __________.

are genetically identical to the parent cell

Sister chromatids __________.

are identical copies of each other formed during DNA synthesis

In a male mammal, every germ cell that undergoes meiosis in the production of gametes gives rise to __________ sperm.

four

Sister chromatids are __________.

identical copies of a chromosome

Which of the following statements best describes the advantage that sexual reproduction likely provides over asexual reproduction?

Although energetically more costly than asexual reproduction, sexual reproduction leads to different combinations of alleles that could provide adaptability in a changing environment.

During which phase of karyokinesis (mitosis) do duplicated chromosomes separate?

Anaphase

What is the difference between a benign tumor and a malignant tumor?

Cells of benign tumors do not metastasize; those of malignant tumors do.

Why do cells undergo mitosis? Why do cells undergo meiosis?

Cells undergo mitosis for growth, repair, and replacement, whereas meiosis is used to prepare for sexual reproduction.

Which of the following human cells contain 46 chromosomes?

Liver cells

A biochemist measured the amount of DNA in cells growing in the laboratory and found that the quantity of DNA in the cells doubled __________.

G1 and G2 phases

Which of the following contributes to genetic variation in sexually reproducing species?

Independent assortment, crossing over, and random fertilization

Which of the following contributes to genetic variation in sexually reproducing species?

Internal fertilization, spindle formation, and crossing over

What is the longest stage in the cell cycle? (In other words, in which stage do cells spend the bulk of their time?)

Interphase

What does a duplicated chromosome consist of?

It consists of two sister chromatids.

You would be unlikely to see which of the following human cells dividing?

Nerve cell

A cell entering mitosis with 32 chromosomes will produce daughter cells with __________.

None of the listed responses is correct.

Which event occurs only during prophase I of the first meiotic division?

Synapsis of homologous pairs occur

In which stage of the cell cycle does DNA replication occur?

Synthesis (S) phase

Which of the following is a basic difference between Mendel's particulate hypothesis and the hypothesis of blending inheritance?

The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring and that these contributions cannot then be separated.

What is the cell cycle? Do all cells go through the cell cycle?

The cell cycle is the series of steps leading to the production of daughter cells from a mother cell. Not all cells are going through the cell cycle.

Huntington's disease is an example of a genetic disorder caused by __________.

a lethal dominant allele that afflicts an individual later in life

If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be __________.

all of the dominant phenotype

The complex of DNA and protein that makes up a eukaryotic chromosome is properly called __________.

chromatin

A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of alleles that are __________.

codominant

The cleavage furrow forms during which stage of mitosis and cell division of an animal cell?

cytokinesis

During interphase, the genetic material of a typical eukaryotic cell is __________.

dispersed in the nucleus as long strands of chromatin

Cytokinesis refers to __________.

division of the cytoplasm

Observations of cancer cells in culture support the hypothesis that cancer cells __________.

do not exhibit density-dependent inhibition

Human somatic cells contain __________ set(s) of chromosomes and are therefore termed __________.

two; diploid

Assume that you are dealing with a species in which the number of chromosomes in each somatic cell is 14. How many sister chromatids are present in the early telophase of mitosis?

0

After obtaining two heads from two tosses of a coin, the probability of obtaining a head on the next toss is __________.

1/2

If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?

1/2

In the F2 of a dihybrid cross involving two independently assorting genes, what proportion of the offspring will be true-breeding?

1/4

A cell biologist carefully measured the quantity of DNA in grasshopper cells growing in cell culture. Cells examined during the G2 phase of the cell cycle each contained 200 units of DNA. What would be the amount of DNA at G1 of the cell cycle in a daughter cell of one of these cells?

100 units

When not engaged in the processes leading to cell division, how many chromosomes from your mother are present in the nucleus of each of your somatic cells?

23

Flower color in snapdragons is an example of incomplete dominance. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the progeny plants will be __________.

25% red, 50% pink, and 25% white

Assume that in guinea pigs, the brown coat color allele (B) is dominant over red (b), and the solid color allele (S) is dominant over spotted (s). The F1 offspring of a cross between true-breeding brown, solid-colored guinea pigs and red, spotted guinea pigs are crossed. What proportion of their offspring (F2 generation) would be expected to be red and solid-colored?

3/16

The egg (ovum) of a rabbit contains 22 chromosomes. How many chromosomes are in the somatic (body) cells of a rabbit?

44

In a diploid cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing __________ chromosomes.

5

A woman with type O blood is expecting a child. Her husband is type A. Both the woman's father and her husband's father had type B blood. What is the probability that the child will have type O blood?

50%

What is a locus?

The precise location of a gene on a chromosome

You would know a dividing cell was a plant cell rather than an animal cell if you saw that __________.

it had formed a cell plate

In sexually reproducing species, the chromosome number remains stable over time because __________ and __________ always alternate.

meiosis; fertilization

Heart disease, diabetes, cancer, alcoholism, and many mental illnesses can best be described as __________.

multifactorial disorders with a possible polygenic component

The synaptonemal complex __________.

physically connects homologous chromosomes during prophase I

A single genetic locus that controls more than one trait is said to be __________.

pleiotropic