Chapter 6: Cell Division

Question 1

Mitosis

Answer 1

Cell division that produces genetically identical daughter cells. Involves prophase, metaphase, anaphase, and telophase.

Question 2

Meiosis

Answer 2

Cell division that occurs in sexually reproducing organisms, and produces haploid cells. Produces gametes, and the nucleus divides twice.

Question 3

Sister Chromatids

Answer 3

Makes up a replicated chromosome.

Question 4

Centromere

Answer 4

The center of a chromosome that holds two chromatids together.

Question 5

Kinetochore

Answer 5

The disc shaped protein on the centromere that attaches the chromatid to the mitotic spindle during division.

Question 6

Cell Cycle

Answer 6

The sequence of growth and cell division.

Two important factors that limit cell growth and promote cell division: Surface area to volume ratio, and the capacity of the nucleus to control the whole cell.

Question 7

Phases of the Cell Cycle

Answer 7

G1: Growth and biochemical activity.
S: Synthesis, DNA replication.
G2: Growth and preparation for mitosis.
Mitosis: The actual splitting of the nucleus.
Cytokinesis:

Question 8

Prophase

Answer 8

• Nucleolus disappears.
• Nuclear envelope disintegrates.
• Chromatin begins to condense.
• Mitotic spindles begin to form.

Question 9

Metaphase

Answer 9

• Chromosomes line up along the equator.
• Centrosomes are situated on opposite sides of the cell.
• Mitotic spindles connect the centrosomes through the kinetochores.

Question 10

Anaphase

Answer 10

• Centrosomes begin to pull the chromosomes and the cell in opposite directions.

Question 11

Telophase

Answer 11

• Centrosomes and chromosomes cluster at their respective ends.
• Chromosomes begin to uncondense to their pre-mitosis state.
• When the individual nucleolus reappear, mitosis is complete.

Question 12

Cytokinesis

Answer 12

The division of the cytoplasm. In animals, a cleavage furrow develops and pinches the cytoplasm, and in plants, a cell plate appears and creates a middle lamella.

Question 13

Density-dependent Inhibition

Answer 13

Cells usually divide until they become too crowded. Cancer cells defy this, however.

Question 14

Anchorage Dependence

Answer 14

Cells must be anchored to something to divide, such as a Petri dish or extracellular membrane. Cancer cells also defy this.

Question 15

Meiosis I

Answer 15

Where the homologous chromosomes separate. Involves synapsis and crossing over.

Question 16

Prophase I

Answer 16

• Crossing over (nonsister chromatids exchanging genetic material).
• Synapsis (pairing of homologues).
• Chiasmata

Question 17

Metaphase I

Answer 17

• Chromosomes line up double file along the equator of the cell.
• Spindle fibers connect at the kinetochores.

Question 18

Anaphase I

Answer 18

• Homologous chromosomes are separated as they are pulled in opposite directions by the spindle fibers.

Question 19

Telophase I and Cytokinesis I

Answer 19

• Chromosomes are pulled apart until they reach the opposite ends of the cell.
• Cytokinesis I usually occurs simultaneously with Telophase I, and splits the cell into two haploid.

Question 20

Three Types of Genetic Variation

Answer 20

1. Independent Assortment of Chromosomes: each chromosome has two ways it can line up at the metaphase plate during meiosis I, which is randomly decided.
2. Crossing Over: the chromosomes randomly trade DNA segments.
3. Random Fertilization: the ovum and sperm have millions of chromosome options.

Question 21

Apoptosis

Answer 21

Programmed cell death.