4.6-7: Cell Cycle (mitosis)

Question 1

The cell division process is an integral part of life. What does it allow for?

Answer 1

• the reproduction of cells, growth of cells, and tissue repair

Question 2

What is the cell cycle?

Answer 2

The life of a cell from its formation until it divides

Question 3

Before cell division, cells must organize and package their DNA. Explain this process. (4 steps)

Answer 3

1. DNA associates with and wraps around proteins known as histones to form nucleosomes
2. strings of nucleosomes form chromatin
   - when a cell is not actively dividing, chromatin is in a non-condensed form
3. After DNA replication, chromatin condenses to form a chromosome
4. Since the DNA was replicated, each chromosome has a duplicated copy. So the copies join together to form sister chromatids

Question 4

What is a centromere?

Answer 4

The region on each sister chromatid where they are mostly closely attached

Question 5

What is a kinetochore?

Answer 5

Proteins attached to the centromere that link each sister chromatid to the mitotic spindle

Question 6

What is a genome?

Answer 6

• all of a cell’s genetic information (DNA)

Question 7

What is the genome for prokaryotes? (Ex. Bacteria, archaea)

Answer 7

Singular, circular DNA

Question 8

What is the genome for eukaryotes? Or like, how many chromosomes etc. (2)

Answer 8

• one or more linear chromosomes
• every eukaryote has a specific number of chromosomes
  Ex. Humans 46, chimps 48, elephants 56

Question 9

What are homologous chromosomes? Give an example

Answer 9

• carry the same genetic trait, but aren’t identical
  Ex. You inherit one copy of chromosomes from mom, and a copy from dad. Both coded for eye colour, but your mom had brown, dad had blue

Question 10

What are the two types of cells?

Answer 10

Somatic and gametes

Question 11

What are somatic cells? How do they divide? (5)

Answer 11

• body cells
• Diploid (2n) where n represents the # of unique xmes
  — 2 set of xmes, one set from each parent
• divide via mitosis
  Humans: 2n = 46, 23 From mom and 23 from dad

Question 12

What are gametes? How do they divide? (4)

Answer 12

• reproductive cells (egg/sperm)
• Haploid (n) so one set of xmes
• divide my meiosis
• humans: n= 23

Question 13

The cell cycle consists of alternating phases of ___

Answer 13

Interphase and mitosis

Question 14

Show a line diagram of the cell cycle. Include interphase and it’s phases, mitosis, and cytokinesis.

Answer 14

Interphase (oG1 → S → G2) → mitosis → cytokinesis

Question 15

What is interphase? What percentage of the cell cycle does it take up?

Answer 15

• The largest portion of the cell cycle (90%)

Question 16

In order, what are the phases in interphase?

Answer 16

1. G1 “first gap” phase
2. S “synthesis” phase
3. G2 “second gap” phase

Question 17

What is G1 “first gap” phase of interphase?

Answer 17

The cell grows and carries out normal functions

Question 18

What occurs in S “synthesis” phase of interphase?

Answer 18

DNA replication and chromosome duplication occurs (single stranded xmes become double stranded sister chromatids)

Question 19

What occurs in G2 “second gap” phase of interphase?

Answer 19

Final growth and preparations for mitosis

Question 20

What occurs in M phase? Remember interphase → mitosis → cytokinesis pathway. (3)

Answer 20

Mitosis: nucleus divides
- mitosis results in 2 identical diploid daughter cells
Cytokinesis: cytoplasm divides

Question 21

What are the 5 stages of mitosis?

Answer 21

1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase and cytokinesis

Question 22

What are the key events in prophase? (5)

Answer 22

1. Chromatin condenses
2. Nucleoli disappear
3. Duplicated chromosomes appear as sister chromatids (they are identical)
4. Mitotic spindle begins to form
5. Centrosomes move away from each other

Question 23

Chromatin condenses in prophase. What does that mean?

Answer 23

• DNA becomes tightly wound around histones to become chromosomes

Question 24

What are the key events in prometaphase? (2)

Answer 24

1. nuclear envelope fragments (breakdown)

2. Microtubules enter nuclear area and some attach to kinetchores

Question 25

What are the key events in metaphase? (3)

Answer 25

1. Centrosomes are at opposite poles
2. Chromosomes line up at the metaphase plate (or equator)
3. Microtubules are attached to the kinetochore

Question 26

What are the key events in anaphase? (2)

Answer 26

1. sister chromatids separate and move to opposite ends of the cell due to microtubules shortening
2. Cell elongates

Question 27

What are the key events in telophase and cytokinesis? (3)

Answer 27

1. Two daughter nuclei form
2. Nucleoli reappear (remember nucleoli make ribosomes)
3. Chromosomes become less condensed (into chromatin)

Question 28

What occurs in cytokinesis in animals?

Answer 28

• a cleavage furrow appears due to contractile ring of actin filaments

Question 29

What occurs in cytokinesis in plants? (2)

Answer 29

• vesicles produced by the Golgi travel to the middle of the cell and form a cell plate
• the cell plate contains the cell wall (made of cellulose)

Question 30

Does mitosis maintain chromosome number?

Answer 30

• maintains chromosome number (2n) but increases cell number (see pg 40)