Ever wondered why some people are more likely to get certain types of cancer? It's all about our genes.

Yes, genetics play a big role in determining your risk of cancer. Wondering what causes this gene mutation? How do people inherit it? What are the existing types?

Karetrip is here to answer your queries. In this blog, we will help you understand the connection between genetics and cancer. Let’s dive in.

What Causes Gene Mutations ?

Gene mutations cause genes from working properly. Genes that have mutations and cause cancer are called cancer genes. Gene mutations are caused in the following instances:

• When we are born with a mutated gene that is either inherited from a parent or that develops in an embryo.
• Being exposed to something that damages our genes such as smoking.
• Old age causes genes to wear out .

Types of Cancer Genes

There are mainly three types of Cancer genes. They are:

• Oncogenes: These are mutated genes that cause cells to grow out of control and that can lead to cancer. Normal genes called Proto-oncogenes promote cell growth but when they are mutated they become Oncogenes.

Properties of Oncogenes include:

Mutations that are caused in proto-oncogenes are acquired.

Having a mutation in just one of the pairs of a particular proto-oncogene is usually enough to cause a change in cell growth and the formation of a tumour.

• Tumour suppressor genes - These types of genes are normally present in our cells. They slow cell growth and division, repair mistakes in DNA and tell cells when to die (a normal process called apoptosis or programmed cell death).

These genes help us protect against cancer. When a tumour suppressor gene is mutated, this can lead to tumour formation or growth.

Properties of tumour suppressor genes include:

• Both copies of a specific tumour suppressor gene pair need to be mutated to cause a change in cell growth and tumour formation to happen.

• Mutations in tumour suppressor genes are often acquired. Mutations in both copies of a tumour suppressor gene pair may happen as the result of ageing, environmental factors, or both.

• Most of the genes linked to hereditary cancer are tumour suppressor genes. But most mutations in tumour suppressor genes are not inherited.

DNA repair genes - These types of genes fix mistakes in other genes that may happen when DNA is copied . When these genes are mutated , they can't fix mistakes in oncogenes and tumor suppressor genes and this will cause cancer .

Properties of DNA repair genes include:

• Mutations in DNA repair genes can be inherited from a parent.

• They can also be caused due to age and environmental factors .

• DNA repair genes need mutations in both copies of the gene pair for the process of tumour formation to happen.

Genes That Cause Cancer

There are different genes that cause cancer. They are:

• BRCA gene mutations
• TP53 gene mutations
• DNA mismatch repair genes
• Adenomatous polyposis coli gene
• HER2 (ERBB2) gene mutations
• BCR-ABL fusion gene
• KRAS gene mutations
• EGFR gene mutations
• ALK gene mutations
• BRAF gene mutations
• NTRK gene fusions

BRCA gene mutations

These are tumour suppressor genes that prevent cancer. But when BRCA genes get mutated , they increase the risk of developing cancer .

There are two BRCA mutations that cause cancer: BRCA1 and BRCA2.

These gene mutations increase the risk of breast cancer and ovarian cancer in women. BRCA2 causes high risk of male breast cancer and prostate cancer.

BRCA2 also causes a high risk to both men and women in developing pancreatic cancer.

TP53 gene mutations

This is a tumour suppressor gene. This controls cell growth and cell division.

TP53 sends signals to other genes to help repair damaged DNA. When this gene is mutated,it causes damaged DNA cells to grow and divide uncontrollably.

This type of gene mutations are common and occur in more than 50% of cancers.

DNA mismatch repair genes

MLH1, MSH2, MSH6 and PMS2 are DNA mismatch repair genes that prevent errors in DNA when it is copied as cells divide. Mutations in these genes increase the risk of developing colorectal and uterine (endometrial) cancers.

These mutations also pave the way for the risk of stomach, kidney, bladder and ovarian cancers.

Adenomatous polyposis coli gene (APC)

This is a tumour suppressor gene that controls cell growth. Mutations in APC cause the development of colorectal, small intestine and pancreatic cancers.

HER2 (ERBB2) gene mutations

The HER2 gene is also known as ERBB2 gene.HER2 stands for human epidermal growth factor receptor 2.

This is an oncogene and protein on the cell surface that causes cell growth. When extra HER2 protein is there in a cancer , it is HER2 overexpression or a HER2-positive cancer.

Some of the breast, esophageal and stomach cancers are HER2-positive.

BCR-ABL fusion gene

This gene is also called Philadelphia Chromosome that is formed when pieces of chromosomes 9 and 22 break off and change places.

An enzyme called tyrosine kinase is made by this gene that causes blood cells in the bone marrow to grow abnormally. This causes chronic myelogenous leukemia (CML).

Around 95% of people with CML and about 25% of adults with acute lymphocytic leukemia (ALL) have the BCR-ABL fusion gene.

KRAS gene mutations

KRAS genes are involved in cell growth, cell maturation and cell death.Mutated KRAS genes cause non-small lung cancer, colorectal cancer and pancreatic cancer.

EGFR gene mutations

EGFR is associated with cell growth and cell survival. Mutated EGFR is found in some cancer types such as non - small cell lung cancer.

ALK general mutations

The anaplastic lymphoma kinase (ALK) gene sends signals to proteins that make cells grow and divide. Mutations in this gene cause cancer .

Around 5% of non -small lung cancers have mutations in the ALK gene.

BRAF gene mutations

BRAF is a gene found on chromosome seven that encodes a protein also called BRAF. This protein plays a role in cell growth by sending signals inside the cell and helps in cell division as well.

Mutation in BRAF makes it work incorrectly.

Around half of all melanomas have mutations in the BRAF gene. This causes the making of abnormal proteins which cause melanoma cells to grow and divide.

NTRK gene fusions

The neurotrophic tyrosine receptor kinase (NTRK) gene tells nerve cells to make a protein that helps the cells send information about sensations like pain, temperature and touch.

When a piece of the NTRK gene breaks off and joins with another gene, it is called a NTRK gene fusion. This process leads to development of abnormal proteins called TRK fusion proteins which leads to cancer.

These types of genes are found in thyroid, colon, lung and primary brain tumours.