Effects of mutations in oncogenes and tumour suppressing genes

Oncogenes are genes that have the potential to cause cancer. They play critical roles in cell growth, differentiation, and survival. Mutations in these genes can contribute to the development of cancer.
Hyperactive gene protein product: Oncogenes typically produce gene proteins that are hyperactive or are produced in excessive amounts. This accelerates cellular growth and division, which can lead to the development of tumours.
One-hit hypothesis: According to this hypothesis, a single mutation in one allele of a gene can cause it to become an oncogene. This is in contrast to tumour-suppressing genes which usually need two mutations to become deactivated, known as the “two-hit hypothesis”.
Recessive mutations: Mutations in oncogenes are often dominant - they can bring about abnormal conditions even if there’s only one copy of the mutation.
Proto-oncogenes: Normal versions of oncogenes, known as proto-oncogenes, regulate cell growth and differentiation. When these genes are mutated, they can get stuck in the “on” position and produce too much of a protein, leading to uncontrolled cell growth.

Tumour suppressor genes protect a cell from one-step on the path to cancer. They repair DNA mistakes, slow down cell division, or tell cells when to die. When these genes don’t work properly, cells can grow out of control, which can lead to cancer.
Loss or inactivation: Mutations to tumour suppressor genes often result in a loss or inactivation of the gene’s function. This lack of regular function can lead to uncontrolled cell growth and the formation of tumours.
Two-hit hypothesis: Most tumour suppressor genes adhere to the two-hit hypothesis – this theory proposes that both alleles of a tumour suppressor gene must be mutated before an effect is seen.
Guardian of the genome: The TP53 protein, encoded by the TP53 gene, is often referred to as the ‘guardian of the genome’. It stops the cell cycle if it detects DNA damage and initiates repair. If TP53 has a mutation and doesn’t function properly, this can lead to genetic instability - a key factor in cancer development.
Examples: Examples of tumour suppressor genes include BRCA1 and BRCA2. Mutations in these genes can hinder their ability to produce proteins that repair DNA, leading to an increased risk of breast and ovarian cancer.