Gene Regulation: Tumour Suppressor Genes | A-level Biology | OCR, AQA, Edexcel

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The key points covered in this video include:

1. Tumour Suppressor Genes
2. p53 Tumour Suppressor Genes

Tumour Suppressor Genes

Tumour suppressor genes are important in the regulation of the cell cycle - they inhibit cell division. Tumour suppressor genes also help repair DNA that has been damaged by mutagens. If the DNA cannot be repaired, tumour suppressor genes also instruct these cells to die in a process called apoptosis. If a tumour suppressor gene is mutated, it can lead to it becoming inactive. This means that cell division is no longer inhibited and cells will start to divide at an increased rate. Mutations very quickly build up in these rapidly dividing cells as the tumour suppressor genes are not able to repair damaged DNA. Most of these mutant cells will die but the ones that survive will carry on dividing and form tumours.

p53 Tumour Suppressor Gene

The tumour suppressor gene p53 (or tp53) codes for the transcription factor p53. This transcription factor plays many roles in preventing cancer: p53 activates DNA repair proteins, p53 halts the cell cycle at the g1/S checkpoint in order to allow time for the DNA to be repaired before DNA replication, p53 also initiates apoptosis in damaged cells. Mutations prevent production of p53 and cells with damaged DNA continue ot divide, leading to cancer.

Summary

Tumour suppressor genes inhibit cell division which helps suppress tumours
Mutations in tumour suppressor genes cause them to become inactive
This can result in the uncontrolled division of cells
One example of a tumour suppressor gene is p53
p53 codes for the protein p53 which has many roles including:
1) Activation of DNA repair proteins
2) Halting the cell cycle before DNA replication to allow DNA repair
3) Initiating apoptosis in damaged cells
Inactivation of the p53 gene results in the uncontrolled division of cells that rapidly accumulate mutations
This results in cancer