Ch. 12 HW/CC Answers

The centromere is a region in which

chromatids remain attached to one another until anaphase.

If there are 20 chromatids in a cell, how many centromeres are there?

10

Starting with a fertilized egg (zygote), a series of five cell divisions would produce an early embryo with how many cells?

32

Where do the microtubules of the spindle apparatus originate during mitosis in both plant and animal cells?

Centrosome

A particular cell has half as much DNA as some other cells in a mitotically active tissue. The cell in question is most likely in

G1

If cells in the process of dividing are subjected to colchicine, a drug that interferes with the formation of the mitotic spindle apparatus, at which stage will mitosis most likely be arrested?

Metaphase

At which part of the cell cycle would you see a chromosome that looks like this? Give your reasons.

Mitotic Prometaphase or Metaphase. The picture shows 2 chromatids, tightly coiled, still joined at the centromere

At which phase of mitosis do the duplicated centrosomes first begin to move apart in animal cells?

Prophase

During which phase of the cell cycle is DNA copied?

S

A chicken has 78 chromosomes in its somatic cells. How many chromosomes did the chicken inherit from each parent? How many chromosomes are in each of the chicken's gametes? How many chromosomes will be in each somatic cell of the chicken's offspring.

The chicken inherited 39 chromosomes from each parent. There are 39 chromosomes in each of the chicken's gametes. There will be 78 chromosomes in each somatic cell of the chicken's offspring.

Which of the following best describes how chromosomes move toward the poles of the spindle during mitosis?

The chromosomes are "reeled in" by the contraction of spindle microtubules, and motor proteins of the kinetochores move the chromosomes along the spindle microtubules.

What is a cleavage furrow?

a groove in the plasma membrane between daughter nuclei

Through a microscope, you can see a cell plate beginning to develop across the middle of a cell and nuclei forming on either side of the cell plate. This cell is most likely

a plant cell in the process of cytokinesis.

Which of the following best describes the kinetochore?

a structure composed of several proteins that associate with the centromere region of a chromosome and that can bind to spindle microtubules

During which phase of mitosis do the chromatids become chromosomes?

anaphase

In the cells of some organisms, mitosis occurs without cytokinesis. This will result in

cells with more than one nucleus.

In which group of eukaryotic organisms does the nuclear envelope remain intact during mitosis?

dinoflagellates and diatoms only

Vinblastine is a standard chemotherapeutic drug used to treat cancer. Because it interferes with the assembly of microtubules, its effectiveness must be related to

disruption of mitotic spindle formation.

When are chromosomes first visible?

prophase

Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, Taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, Taxol must affect

the formation of the mitotic spindle.