SB2 - Cells and Controls ✓

Question 1

SB2a - How are tumours formed?

Answer 1

When cells mutate, they can become cancer cells.

This means that they will divide even when they don’t require to divide.

Question 2

SB2a - How many types of chromosomes are in a human cell and what is it called when these are alone or paired up?

Answer 2

23 types of chromosomes.

When they are paired up to have 46 chromosomes this is a diploid cell and a haploid cell only has 23 chromosomes.

Gametes are haploid cells while all other cells in a human are diploid.

Question 3

SB2a - Describe stages of mitosis

Answer 3

Mitosis:

Interphase:
Copies of the chromosomes are formed in the nucleus
Prophase
The nucleus starts to break up and spindle fibres appear.

Metaphase:
The chromosomes are lined up on the spindle fibre across the middle of the cell

Anaphase:
The chromosome copies are separated and moved to either side of the cell

Telophase:
A membrane forms around each set of chromosomes to from a nuclei

Cytokinesis:
Cell surface membrane forms separating the two cells (In plants, a cell wall is also formed)

Question 4

SB2a - What are the products of mitosis called?

Answer 4

Daughter cells

Question 5

SB2a - What type of organisms do not require mitosis to occur?

Answer 5

Unicellular organisms

Question 6

SB2a - Why does asexual reproduction require mitosis?

Answer 6

As asexual reproduction only needs one parent, the offspring will have the same DNA as the parent.

As the offspring are clones and their chromosomes are identical, their cells are formed by mitosis.

Question 7

SB2a - Why is mitosis important in organisms?

Answer 7

Asexual Reproduction

Growth

Repairing damage

Cell Replacement

Question 8

SB2b - Define growth.

Answer 8

The increase in size as a result of an increase in size of or numbers (due to cell division) of cells.