Paper 1 - Mitosis

Question 1

What is the cell cycle? Name the 3 parts and what happens

Answer 1

There are 3 parts of the cell cycle

Interphase - Just before mitosis, the DNA in the nucleus copies itself exactly (forms x-shaped chromosomes)

Mitosis - Chromosomes line up along the centre of the cell where cell fibres pull them apart

Cytokinesis - The cell cytoplasm and membrane divides to produce two daughter cells; each new cell has a copy of each of the chromosomes

Question 2

Give three uses of mitosis in organisms

Answer 2

Mitosis is required for:
Growth: mitosis produces new cells

Repair: to replace damaged or dead cells

Asexual reproduction: mitosis produces offspring that are genetically identical to the parent

Question 3

Name the four stages of mitosis in order

Answer 3

PMAT:
Prophase
Metaphase
Anaphase
Telophase

Question 4

Describe what happens during interphase

Answer 4

Interphase - Just before mitosis, the DNA in the nucleus copies itself exactly (forms x-shaped chromosomes)

Question 5

Describe what happens during prophase

Answer 5

DNA condenses, chromosomes become visible and the nuclear membrane breaks down

Question 6

Describe what happens during metaphase

Answer 6

Metaphase - Chromosomes line up on the equator of the cell (the metaphase plate)

Question 7

Describe what happens during anaphase

Answer 7

Anaphase - Fibres split the chromosomes down the centre and pull one chromatid to either side of the cell

Question 8

Describe what happens during telophase

Answer 8

Telophase - New membranes form around the chromosomes at either end of the cell

Question 9

what happens during cytokinesis

Answer 9

Cytokinesis - The cell cytoplasm and membrane divides to produce two daughter cells; each new cell has a copy of each of the chromosomes

Question 10

What are meristems and where are they found?

Question 11

What happens when a cell becomes cancerous

Answer 11

Cells grow then divide by mitosis only when we need new ones. This is when we’re growing or need to replace old or damaged cells.

When a cell becomes cancerous, it begins to grow and divide uncontrollably. New cells are produced even if the body does not need them. A group of cancerous cells produces a growth called a tumour.

Question 12

Name two types of tumour and describe their characteristics

Answer 12

Type of tumour

Benign Grow slowly. Usually grow within a membrane, so can easily be removed. Do not invade other parts of the body.

Malignant Grow quickly. Invade neighbouring tissues and can spread to other parts of the body in the bloodstream. As the tumour grows, cancer cells detach and can form secondary tumours in other parts of the body. This process is called metastasis.

Question 13

What causes cancer?

Answer 13

• genetic factors that increase the likelihood of developing some cancers.
• chemicals or carcinogens

Lifestyle factors:
viruses linked with cancer, such as the human papilloma virus (HPV), being spread from person to person through sexual intercourse

the chemical carcinogens in cigarette smoke increasing the risk of lung cancer

alcohol intake is linked with certain cancers

exposure to ultraviolet radiation, part of which is ionising, during sunbathing or outdoor activities, leading to the development of skin cancers

diet, including fat and salt intake, increases the risk of cancer

Question 14

What type of cells are not produced by mitosis?

Answer 14

Gametes (sperm and ova)