Chapter 6: Cell Divisions

Question 1

What occurs in the G1 growth phase in interphase?

Answer 1

• Proteins from which organelles are synthesised are produced.
• Cell increases in size.
• Organelles replicate.

Question 2

What occurs in the S (synthesis) phase of interphase?

Answer 2

• DNA replicated in the nucleus.

Question 3

What occurs in the G2 phase of interphase?

Answer 3

• Duplicated DNA checked for errors.
• Cell continues to increase in size.
• Energy stores increased.

Question 4

What does G1 checkpoint check for?

Answer 4

• Cell size.
• Nutrients.
• Growth factors.
• DNA damage.

Question 5

What does G2 checkpoint check for?

Answer 5

• DNA replication.
• DNA damage.
• Cell size.

Question 6

What does spindle assembly checkpoint check for?

Answer 6

• Attachment of chromosome to spindle.

Question 7

Outline process of copying + separating of chromosomes.

Answer 7

1. DNA wrapped around histones.
2. Before cell divides, DNA in nucleus needs to replicate.
3. 2 replicas held together by centromere.
4. Each chromosome contains two replica strands –> sister chromatid.
5. Each chromatid ends up in different new cells.
6. Chromatin –> supercoiled –> visible, short, sturdy, move around easily.

Question 8

Outline mitosis.

Answer 8

Prophase:

• Nucleolus disappears + nuclear envelope disintegrates.
• Chromatin coil + condenses –> forms chromosomes.
• Centrioles –> assist in spindle formation –> attach to centromeres –> start to move chromosomes to centre of cell.
• Microtubules –> form spindle shaped structures –> attach to poles of the cell.

Metaphase:

• Chromosomes pulled by spindle to centre of cell + align on the metaphase plate.

Anaphase:

• Centromeres holding chromatids divide.
• Chromatids separated + pulled to opposite poles of cell by shortening spindle fibres.
• ‘V’ shape –> due to spindle pulling chromatids through liquid cytosol.

Telophase:

• Nucleolus reforms.
• Nuclear envelope reforms.
• Cytokinesis begins.
• Chromosomes assemble at each pole + uncoil.

Question 9

Adaptations of neutrophils.

Answer 9

• Many lysosomes.
• Many mitochondria.
• Many microfilaments.
• Many receptor sites on cell surface membrane.
• Many ribosomes.

Question 10

Define totipotent.

Answer 10

Stem cell can differentiate into any cell type.

Question 11

Define pluripotent.

Answer 11

Can differentiate into all tissue types but cannot make whole organisms.

Question 12

Define multipotent.

Answer 12

Can differentiate into a range of cells within a specific tissue type.

Question 13

What happens if genetic info not checked?

Answer 13

• Mutation.
• Daughter cells will not receive identical genetic info.
• Proteins not made/do not function.

Question 14

Why do prokaryotes not undergo meiosis?

Answer 14

• No nucleus.
• Single chromosome.
• Need homologous chromosomes for meiosis.

Question 15

Outline overall importance of strict regulation of cell cycle.

Answer 15

• So cell doesn’t divide too often.
• Cell divides at right time.
• Chromosomes are in correct position.
• DNA has been checked.
• Cell is the right size.