Biology Ch. 8

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

Benign tumors do not metastasize; malignant tumors do.

Which of the following occurs during mitosis?

Chromatids separate.

Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?

Extra copies of the other somatic chromosomes are probably fatal.

Consider the cell cycle shown below. Cells will usually divide if they receive the proper signal at a checkpoint in the _____ phase of the cell cycle

G1

Which of the following is a key difference between meiosis and mitosis?

Synapsis occurs.

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

Synapsis of homologous pairs occurs.

If the diploid number of chromosomes in a certain animal is 6 (2n = 6), there are three sets of two homologous chromosomes each, or three pairs. How do these three pairs align and separate in meiosis?

They align and assort independently to form any of eight different combinations.

During cell division, what role do centrosomes play?

They organize the microtubules.

Chromatids are _____.

identical copies of each other if they are part of the same chromosome

When we say that an organism is haploid, we mean that _____.

its cells each have one set of chromosomes

In some organisms such as certain fungi and algae, cells undergo mitosis repeatedly without subsequently undergoing cytokinesis. What would be the consequence of this?

large cells containing many nuclei

In humans, the _____ determines the sex of the offspring because _____.

male ... the male can contribute either an X or a Y chromosome

Variation occurs when chromosomes are shuffled in _____.

meiosis

At which stage of mitosis are chromosomes lined up in one plane in preparation for their separation to opposite poles of the cell?

metaphase

Which of the following is a correct representation of an event that occurs in mitosis?

metaphase—chromosomes line up on the equatorial plane.

After fertilization, the resulting zygote begins to divide by _____.

mitosis

During meiosis, homologous chromosomes sometimes "stick together" and do not separate properly. This phenomenon is known as _____.

nondisjunction

Down syndrome can be the result of _____.

nondisjunction of chromosome 21 during meiosis

The term binary fission is best applied to _____.

prokaryotes

At which point do centrosomes begin to move apart to the opposite poles of the cell in a dividing human liver cell?

prophase

In the telophase of mitosis, the mitotic spindle breaks down and the chromatin uncoils. This is essentially the opposite of what happens in _____.

prophase

Crossing over occurs during _____.

prophase I

Synapsis occurs during _____.

prophase I

During anaphase II, _____.

sister chromatids separate and migrate toward opposite poles

The kinetochores are _____.

sites at which microtubules attach to chromosomes

An example of a cell that is 2n is a _____.

somatic cell

At a critical point in meiosis, the chromosomes do not replicate. This occurs between _____.

telophase I and prophase II

Chromatids form during _____.

the S phase of interphase

DNA replication occurs in _____.

the S phase of interphase

One event occurring during prophase is _____.

the beginning of the formation of the mitotic spindle

Individual chromosomes are usually observed with a light microscope during mitosis, even though cells spend more time in interphase. This is because _____.

they have uncoiled to form long, thin strands

Mitosis and cytokinesis result in the formation of _____; meiosis and cytokinesis result in the formation of _____.

two diploid cells ... four haploid cells

At the end of telophase I of meiosis, as cytokinesis occurs, there are _____.

two haploid cells

During anaphase I, _____.

homologues separate and migrate toward opposite poles

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 contained 200 units of DNA. What would be the amount of DNA in one of the grasshopper daughter cells?

100 units

How many pairs of autosomes do humans have?

22

In humans, the haploid number of chromosomes is 23. Independent assortment has the possibility of producing _____ different gametes.

2^23

Each cell in an individual with Down syndrome contains _____ chromosomes.`

47

In a cell containing 10 chromosomes, meiosis results in the formation of daughter cells containing _____ chromosomes

5

A human bone marrow cell, in prophase of mitosis, contains 46 chromosomes. There are _____ chromatids.

92

Which of the following indicates Turner syndrome?

XO

Which of the following is a normal human female?

XX

Consider the photograph of a karyotype. This is _____.

a photograph of all a person's chromosomes

Crossing over is important because it _____.

allows the exchange of genes between homologous chromosomes

Unless the chromosomes were stained to show band patterns, a karyotype would usually be unable to show _____.

an inversion

The phase of mitosis during which the chromosomes move toward separate poles of the cell is _____.

anaphase

Single sister chromatids are found in cells at mitotic _____.

anaphase and telophase

A cleavage furrow forms in an animal cell during _____.

cytokinesis

The function of mitosis is to produce daughter cells that _____.

are genetically identical to the parent cell (assuming no mutation has occurred)

Which of the following conditions would result in inhibition of cell division due to density-dependent factors?

being completely surrounded by other cells

In the picture below, the chromosomal region where the nonsister chromatids are crossing over is called a(n) _____.

chiasma

In bacterial cells, binary fission involves _____.

distribution of a copy of the single parental chromosome to each daughter cell

Cytokinesis refers to _____.

division of the cell outside the nuclear material

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

do not exhibit density-dependent inhibition

The diploid phase of the human life cycle begins with _____.

fertilization

Cytochalasin B is a chemical that disrupts microfilament formation. This chemical would interfere with _____.

formation of a cleavage furrow

Consider the photograph shown below. You can determine this is a plant cell rather than an animal cell because it has _____.

formed a cell plate

An organism has a haploid chromosome number n = 4. How many tetrads will form during meiosis?

four

The function of meiosis is to make _____.

four cells with a haploid number of chromosomes

What is the typical result when a diploid cell undergoes meiosis?

four haploid cells

During asexual reproduction, yeast cells can produce _____

genetically identical offspring

Consider the two mice shown below. They have the same chromosomes, carrying genes for the same traits in the same loci, but specifying different versions of the same traits—for example, coat and eye color. These chromosomes are called _____.

homologous chromosomes

In anaphase I, _____.

homologous chromosomes move toward opposite poles