Cell Cycle full

The centromere is a region in which

• chromatids remain attached to one another until anaphase.

• metaphase chromosomes become aligned at the metaphase plate.

• chromosomes are grouped during telophase.

• the nucleus is located prior to mitosis.

• new spindle microtubules form at either end.

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

• 4

• 8

• 16

• 32

• 64

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

• 10

• 20

• 30

• 40

• 80

Suppose a biologist can separate one of a dozen pieces of chromatin from a eukaryotic (animal) nucleus. It might consist of which of the following?

• one-twelfth of the genes of the organism

• two chromosomes, each with six chromatids

• a single circular piece of DNA

• two long strands of DNA plus proteins

• two chromatids attached together at a centromere

At which phase are centrioles beginning to move apart in animal cells?

• telophase

• anaphase

• prometaphase

• metaphase

• prophase

If there are 20 centromeres in a cell at anaphase, how many chromosomes are there in each daughter cell following cytokinesis?

• 10

• 20

• 30

• 40

• 80

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.

• anaphase.

• formation of the centrioles.

• chromatid assembly.

• the S phase of the cell cycle.

Movement of the chromosomes during anaphase would be most affected by a drug that

• reduces cyclin concentrations.

• increases cyclin concentrations.

• prevents elongation of microtubules.

• prevents shortening of microtubules.

• prevents attachment of the microtubules to the kinetochore.

Measurements of the amount of DNA per nucleus were taken on a large number of cells from a growing fungus. The measured DNA levels ranged from 3 to 6 picograms per nucleus. In which stage of the cell cycle did the nucleus contain 6 picograms of DNA?

• G0

• G1

• S

• G2

• M

A group of cells is assayed for DNA content immediately following mitosis and is found to have an average of 8 picograms of DNA per nucleus. How many picograms would be found at the end of S and the end of G2?

• 8; 8

• 8; 16

• 16; 8

• 16; 16

• 12; 16