Cell Division

Question 1

What is a chromosome?

Answer 1

•A linear DNA molecule tightly coiled around proteins

•Contains genes

Question 2

How many chromosomes does the human body contain?

Answer 2

46 chromosomes (23 pairs).

Question 3

What are sex chromosomes?

Answer 3

A pair of chromosomes that determines sex:

Males have an X and a Y chromosome
Females have two X chromosomes

Question 4

What is mitosis?

Answer 4

•A form of cell division that produces two ‘daughter cells’

•Both genetically identical to the parent cell with the same number of chromosomes (46 chromosomes)

•Involves one division

Question 6

Why is mitosis important in organisms? (4)

Answer 6

•Asexual reproduction
•Growth
•Repair of damaged cells
•Cell replacement

Question 7

What is meiosis?

Answer 7

•A form of cell division involved in the formation of gametes

•Chromosome number is halved (23 chromosomes).

•Involves two divisions , producing four gametes

Question 8

What are gametes?

Answer 8

•Sex cells (sperm cells, egg cells).

•Contain half the chromosome number.

Question 9

Why is meiosis important for sexual reproduction?

Answer 9

•Increases genetic variation.

•Ensures that the resultant zygote has a full set of chromosomes.

Question 10

Compare Mitosis and Meiosis (5)

Answer 10

Mitosis:
•Occurs in all non-reproductive cells
•Produces two daughter cells
•Daughter cells genetically identical
•Daughter cells have 46 chromosomes.
•Occurs for the growth, repair and replacement of damaged cells

Meiosis:
•Occurs only in reproductive cells
•Produces four daughter cells
•Daughter cells genetically different
•Daughter cells have 23 chromosomes
•Occurs for the formation of gametes during sexual reproduction

Question 11

What is cancer?

Answer 11

•Non-communicable disease

•Uncontrolled mitosis results in the formation of a primary tumour

•Tumour cells breaks off and spread to other tissues forming secondary tumours