D2.1.16 Consequences of mutations in genes that control the cell cycle (HL)

What happens when tumour suppressor genes are mutated?

The brakes fail, allowing uncontrolled cell division to occur.

Are mutations in tumour suppressor genes dominant or recessive?

They are usually recessive; both copies of the gene must be mutated for loss of function to occur.

What are the consequences of failing tumour suppressor genes?

Unchecked division; Accumulation of mutations; Avoidance of apoptosis.

Why are multiple mutations usually required for cancer to develop?

A single mutation is rarely enough; it typically takes multiple mutations in different genes to fully disrupt the cell cycle.

What are mutagens?

Agents that increase the likelihood of mutations.

Give two types of mutagens.

Chemical (e.g., tobacco smoke); Radiation (e.g., X-rays, UV light).

What is gene amplification in the context of proto-oncogenes?

It is the production of multiple copies of a proto-oncogene, resulting in excessive protein production.

Give an example of a proto-oncogene and its mutation effect.

The Ras gene; a mutation can lock Ras in its active form, continuously sending 'divide' signals.

How can point mutations affect proto-oncogenes?

A single base change can make the protein product hyperactive, leading to uncontrolled cell division.

What are tumour suppressor genes?

Genes that act as brakes on the cell cycle, preventing rapid or inappropriate cell division.

What is the role of the p53 protein?

It halts the cell cycle if DNA is damaged, allowing time for repair, or triggers apoptosis if the damage is irreparable.

What are the three steps in cancer development?

Initiation: a mutation occurs; Promotion: additional mutations increase cell division; Progression: cells gain the ability to invade and metastasize.

What is the difference between proto-oncogenes and oncogenes?

Proto-oncogenes are normal genes that regulate cell division, while oncogenes are mutated forms that promote uncontrolled cell division.

What is the difference between benign and malignant tumours?

Benign tumours remain localized and do not invade other tissues, while malignant tumours spread and cause cancer.