CH 12

Question 1

Mitosis

Answer 1

• the division of the nucleus followed by the division of the cytoplasm (cytokinesis)
  produces two identical daughter cells

Question 2

Meiosis

Answer 2

eukaryotic cell division that can produce sperm
and eggs
- located in our gonads (ovaries or testes) producing gametes

Question 3

Genome

Answer 3

a cell’s genetic information, packaged as DNA

Question 4

Somatic cells

Answer 4

all body cells except sperm and egg have 46 chromosomes, made up of two sets of 23

Question 5

Gametes

Answer 5

human reproductive cells (sperm/eggs) have one set of 23 chromosomes

Question 6

what does each chromosome look like when the cell is not dividing?

Answer 6

a long, thin chromatin fiber

Question 7

what happens to chromatin before cell division but after DNA replication?

Answer 7

chromatin condenses, coils, and folds to make a smaller package

Question 8

Sister chromatids

Answer 8

the identical copies formed by the DNA replication of a chromosomes joined by a centromere

Question 9

how many centromeres are there?

Answer 9

2

Question 10

how many chromosomes did we get from each parent?

Answer 10

23 - one set in egg, and one set in sperm, total of 46

Question 11

how many daughter cells produced by meiosis? are they identical?

Answer 11

4 nonidentical daughter cells, each with half the chromosomes of the parent

Question 12

what includes in mitotic phase of the cell cycle? what phase does mitotic alternate with?

Answer 12

mitosis and cytokinesis, alternates with
the much longer interphase.

Question 13

How many subphases does the interphase have and what are they?

Answer 13

3 subphases
- the G1 phase (“first gap”)
- the S phase (“synthesis”)
- the G2phase (“second gap”).

Question 14

Why do human cell might divide once every 24hours?

Answer 14

the M phase would last less than 1 hour
the S phase might take 10–12 hours, or half the cycle.
○ The rest of the time would be divided between the G1 and G2 phases.
○ The G1 phase varies most in length from cell to cell

Question 15

Mitosis is usually divided into # subphases? and what are they?

Answer 15

5 subphases: prophase, prometaphase,
metaphase, anaphase, and telophase

Question 16

What process completes mitosis?

Answer 16

Cytokinesis

Question 17

What happens in late interphase? (4)

Answer 17

the chromosomes have been duplicated but are not condensed.
○ A nuclear membrane bounds the nucleus, which contains one or more nucleoli.
○ The centrosome has replicated to form two centrosomes.
○ In animal cells, each centrosome features two centrioles

Question 18

What happens in prophase? (5)

Answer 18

the chromosomes are tightly coiled, with sister chromatids joined together.
○ The nucleoli disappear.
○ The mitotic spindle begins to form. It is composed of centrosomes and the microtubules that
extend from them.
○ The radial arrays of shorter microtubules that extend from the centrosomes are called asters.
○ The centrosomes move away from each other, apparently propelled by lengthening
microtubules

Question 19

What happens in prometaphase?

Answer 19

the nuclear envelope fragments, and microtubules from the spindle interact
with the condensed chromosomes.
○ Each of the two chromatids of a chromosome has a kinetochore, a specialized protein
structure located at the centromere.
○ Kinetochore microtubules from each pole attach to one of two kinetochores.

Question 20

What happens in metaphase?

Answer 20

The spindle fibers push the sister chromatids until they are all arranged at the metaphase plate,
an imaginary plane equidistant from the poles

Question 21

What happens in anaphase?

Answer 21

the centromeres divide, separating the sister chromatids.
○ Each chromatid is pulled toward the pole to which it is attached by spindle fibers.
○ By the end, the two poles have equivalent collections of chromosomes

Question 22

What happens in telophase?

Answer 22

daughter nuclei begin to form at the two poles

○ Nuclear envelopes arise from the fragments of the parent cell’s nuclear envelope and other
portions of the endomembrane system.
○ The chromosomes become less tightly coiled

Question 23

What happens in cytokinesis?

Answer 23

division of the cytoplasm, is usually well under way by late telophase

○ In animal cells, cytokinesis involves the formation of a cleavage furrow, which pinches the
cell in two.
○ In plant cells, vesicles derived from the Golgi apparatus produce a cell plate at the middle of
the cell