Cell Division

Question 1

In body cells what do they contain?

Answer 1

Chromosomes in matching pairs

Question 2

Explain why the chromosomes have to be copied to produce new cells for growth

Answer 2

To replace damaged cells and repair worn out tissue

Question 3

What is mitosis needed for?

Answer 3

• replacement of worn out cells
• repair to damaged tissue
• asexual reproduction

Question 4

What is sexual reproduction?

Answer 4

When gametes join in fertilisation

Question 5

What do gametes contain?

Answer 5

Half the number of chromosomes of body cells

Question 6

Explain why sperm cells are produced in large numbers?

Answer 6

To increase the chance of fertilisation

Question 7

In sexual reproduction what s needed to produce a unique individual?

Answer 7

Half the genes from each parent

Question 8

Explain the advantages or being multicellular

Answer 8

Allows organisms to be larger
Allows for cell differentiation
Allows organisms to be more complex

Question 9

What are new cells for growth produced by?

Answer 9

Mitosis

Question 10

Explain why new cells are genetically identical in mitosis?

Answer 10

Because the DNA replicates

Question 11

In mammals what type of body cells do they have?

Answer 11

Diploid (two copies of each chromosome)

Question 12

Explain why DNA replication must take place

Answer 12

So that all new cells produced have all the DNA of the original cell otherwise the cells would not receive all the chromosomes and genes necessary for life processes

Question 13

What are gametes produced by?

Answer 13

Meiosis

Question 14

Describe gametes

Answer 14

Haploid (contain one chromosome from each pair)

Question 15

Explain how the structure of a sperm cell is adapted to its function

Answer 15

Many mitochondria to provide energy

An acrosome that releases enzymes to digest the egg membrane

Question 16

Explain why fertilisation results in genetic variation

Answer 16

• gametes combine to form a diploid zygote

- genes on the chromosome combine to control the characteristics of the zygote

Question 17

Explain why in meiosis the chromosome number is halved and each cell is genetically different

Answer 17

• one chromosome from each pair separate to opposite poles of the cell in the first division
• chromosomes divide and the copies move to opposite poles of the cell in the second division

Question 18

Describe what happens in mitosis

Answer 18

• chromosomes line up along the centre of the cell
• they then divide
• the copies more to opposite poles of the cell

Question 19

Describe how DNA replication occurs

Answer 19

• the double helix unzips
• new bases pair up with exposed bases on each strand
• an enzyme bonds the new bases together to form complementary strands
• two identical strands of DNA are formed

Question 20

Explain why becoming multicellular requires the development of specialised organ systems

Answer 20

Communication between cells
Supplying the cells with nutrients
Controlling exchanges with the environment

Question 21

Describe the difference between simple organisms which are unicellular and more complex organisms which are multicellular

Answer 21

Single-cell organisms are very small and have to rely on diffusion to obtain glucose and oxygen, to remove waste products
- multicellular are larger and more complex. Require specialised organs to carry out functions like gas exchange and digestion.