2.2 ALL CELLS ARISE FROM OTHER CELLS

Question 1

What is mitosis?

Answer 1

When eukaryotic cells produce two identical daughter cells, with the same chromosome number as their parents (diploid).

Question 2

What are the stages of mitosis, in order?

Answer 2

Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 3

What happens during interphase?

Answer 3

DNA replication of parental chromosomes occur, preparing for the division process. Here, no division is taking place.

Question 4

What happens in prophase?

Answer 4

• Chromosomes shorten and fatten, and first become visible.
• Shows 4 chromosomes per cell.
• The nucleolus and nuclear envelope of the cell disappear.
• Spindle fibres at opposite poles begin to appear.

Question 5

What does a chromosome look like in prophase?

Answer 5

2 chromatid strands held together by a centromere in the middle.

Question 6

What happens in metaphase?

Answer 6

• Chromosomes are pulled by spindle fibres.

- They line up along the equator, with both chromatids facing opposing poles.

Question 7

What happens in anaphase?

Answer 7

• The chromosomes split at the centromere into two chromatids.
• Spindle fibres pull opposite spindle fibres towards opposite poles.

Question 8

What happens in telophase?

Answer 8

• The chromatids reaches opposite poles.
• The spindle apparatus disintegrates.
• The nucleolus and nuclear envelopes start to reform.

Question 9

What happens in cytokinesis?

Answer 9

• The nuclear envelopes and nucleolus’ fully form.
• The cytoplasm divides.
• Leaves two identical daughter cells.

Question 10

What is the cell cycle?

Answer 10

1. DNA replication (interphase)
2. Cellular division (mitosis/meiosis)
3. Cytokinesis (new daughter cells formed)

Question 11

How do prokaryotic cells replicate?

Answer 11

Cellular division any binary fission.

Question 12

Outline the process of binary fission.

Answer 12

1. Circular DNA (1 per cell) and plasmids (variable no.) replicate in the cell.
2. Each circular DNA (2) bind to opposite sides of the cell membrane.
3. The membrane pinches between the DNA causing it to divide.
4. Cytokinesis occurs, and forms two daughter cells.
   - Each daughter cell has 1 circular DNA and a variable number of plasmids.

Question 13

How do cancers form?

Answer 13

Caused by the uncontrolled growth of cell and cell division.

Question 14

What is a tumour?

Answer 14

A clump of cells, caused by the uncontrolled mitotic division.

Question 15

How do cancer treatments reduce the uncontrolled division of cells?

Answer 15

• Stops interphase (chemotherapy)

- Inhibit metaphase, so spindle fibres can’t fully form. This inhibits mitosis.

Question 16

How do viruses divide?

Answer 16

They do not as they are non living.

Question 17

How do viruses replicate?

Answer 17

Inject their DNA / RNA & reverse-transcriptase into host cells, which will metabolise more viral particles.