The cell cycle and mitosis

Question 1

In order, what are the 3 phases of the cell cycle?

Answer 1

• Interphase
• Mitosis
• Cytokinesis

- Interphase not apart of mitosis

Question 2

What happens during interphase?

Answer 2

Cell grows, new organelles made, DNA replicates
- No active division

Question 3

In order, what are the three stages of interphase?

Answer 3

G1 - first gap
S - synthesis of new DNA
G2 - second gap

Question 4

What is the longest phase of the cell cycle?

Answer 4

Interphase

Question 5

What happens during G1 in interphase?

Answer 5

• Cell grows
• New organelles made
• Proteins are made

Question 6

What happens during S phase in interphase?

Answer 6

DNA replicates

Question 7

What happens during G2 in interphase?

Answer 7

• Cell keeps growing
• Proteins needed for cell division are made
• ATP produced

Question 8

In order, what are the four stages of mitosis?

Answer 8

• Prophase
• Metaphase
• Anaphase
• Telophase

Question 9

What happens during prophase in mitosis?

Answer 9

• Chromosomes condense and become visible under a microscope
• Nuclear envelope disintegrates and the nucleolus disappears, leaving chromosomes free in the cytoplasm
• Centrioles (bundles of protein) move to opposite ends of cell and form spindle fibres

Question 10

What happens during metaphase in mitosis?

Answer 10

• Chromosomes line up at the equator of the cell
• Each chromosome attaches to spindle fibres by their centromere

Question 11

What happens during anaphase in mitosis?

Answer 11

• The centromeres divide to separate each pair of sister chromatids
• Spidle fibres contract, pulling the chromatids to opposite pole of the cell
• Each chromatid is pulled by its centromere, causing them to appear ‘v’ shaped

Question 12

What happens during telophase in mitosis?

Answer 12

• Chromatids reach opposite poles of the cell
• Chromatids uncoil and become chromatin again
• A nuclear envelope forms around each set of chromosomes and nucleolus reforms
• Spindle disintegrates
• Two new nuclei produced

Question 13

What happens after mitosis?

Answer 13

Cytokinesis

Question 14

What happens during cytokinesis?

Answer 14

The cytoplasm divides and produces two daughter cells that are genetically identical to one another

Question 15

What is the purpose of chromosomes condensing during prophase?

Answer 15

• Ensures that large amounts of DNA can fit in small space
• Ensures that DNA is organised when daughter cells split

Question 16

What is mitosis important for?

Answer 16

• Growth
• Repair
• Asexual reproduction
• Production of stem cells

Question 17

How do we calculate the mitotic index (MI)?

Answer 17

MI = (Number of cells with condensed chromosomes / total number of cells) x100

Question 18

Why is it important that mitosis is a controlled process?

Answer 18

Uncontrolled mitosis can lead to cancer

Question 19

What is meant by a ‘mutation’?

Answer 19

A change to the base sequence of DNA

Question 20

What factors can increase the risk of mutations?

Answer 20

• UV light
• Smoking
• X-rays
• Genetics

Question 21

Do all mutations lead to cancer?

Answer 21

No
- Mutations are common

Question 22

What are the two types of tumor?

Answer 22

• Begnin
• Malignant

Question 23

What are the characteristics of begnin tumors?

Answer 23

• Non cancerous
• Surrounded by membrane
• Slow growing

Question 24

What are the characteristics of malignant tumors?

Answer 24

• Cancerous
• Large nucleus
• Can grow projections
• Faster growing