1.6 cell division

Question 1

Benign tumor

Answer 1

A benign tumor is usually localised, and does not spread to other parts of the body. Most benign tumors respond well to treatment.

Question 2

Malignant tumour

Answer 2

A malignant tumour is a cancerous growth that is often resistant to treatment. It may spread to other parts of the body and sometimes recur after it has been removed.

Question 3

Oncogene

Answer 3

An oncogene is a mutated gene that contributes to the development of a tumour.

Question 4

Mutagens

Answer 4

These are agents that cause gene mutations.

Question 5

Give three examples of mutagens

Answer 5

• Chemicals that cause mutations that are referred to as carcinogens, such as asbestos or dioxin.
• High-energy radiation, such as X-rays.
• Short-wave ultraviolet light.
• Some viruses such as hepatitis B.

Question 6

Metastasis

Answer 6

Metastasis is the movement of cells from a primary tumour to other parts of the body where they develop into secondary tumours.

Question 7

Process of secondary tumors

Answer 7

• Cancerous cells detach from the primary tumour.
• Some cancerous cells gain the ability to penetrate the walls of lymph or blood vessels and so circulate around the body.
• The circulating cancerous cells invade tissues at different locations and develop, by uncontrolled cell division, into secondary tumours.

Question 8

Cytokinesis Animal cells

Answer 8

• A ring of protein (microfilaments) located immediately beneath the plasma membrane at the equator pulls the plasma membrane inward.
• The inward pull on the plasma membrane produces the characteristic cleavage furrow.
• When the cleavage furrow reaches the centre of the cells, it is pinched apart to form two daughter cells.

Question 9

Cytokinesis in Plant cells

Answer 9

• Golgi apparatus forms vesicles that consist of material to build a new cell wall.
• Vesicles merge and form the cell plate.
• The cell plate grows and divides into two daughter cells.

Question 10

Correlation between smoking and the incidence of cancers.

Answer 10

The longer a person smokes, the higher the risk that the person will develop lung cancer.