What Is a Mutation? How Does It Cause Cancer?

What Is a Mutation? A Brief Overview

Mutation, in the shortest definition, means change . More fully, it means: DNAsingle-base changes or changes in gene structure through deletion, insertion or rearrangement of larger gene or chromosome segments. This change may or may not pass to later generations; inheritance is discussed below.

Cancer Is a Genetic Disease at Cellular Level. In genes controlling proliferation and cell relationships, accumulating mutations result in carcinogenesis (cancer development) .

How Do Mutations Cause Cancer?

DNA is the cell’s central management molecule. Through its genes, it enables vital bodily processes.

To understand mutations, consider DNA’s double helix, with paired nucleotides forming a ladder. Everyday exposures such as tobacco, chemicals, infectious agents and ultraviolet rays can disrupt it and break paired nucleotides. These changes/damage are mutations.

Imagine the genome as a book whose alphabet consists of DNA’s 4 nucleotides and headings represent genes. Deleting letters or tearing pages makes it meaningless. Human gene damage is similar.

DNA Repair Systems

Cells have developed defenses against mutations, called DNA repair systems . Mutations in these systems’ genes are major cancer causes. Cancer cells also repair treatment-damaged genes with them. Developing treatments such as PARP inhibitors targeting repair is a recent focus.

Accumulating DNA Damage Causes Cancer

A single mutation does not suffice for uncontrolled proliferation. Extensive research found 4 or more mutations may cause it.

What Are Examples of Mutations?

Mutations have 2 main classes: hereditary and nonhereditary, or germline (reproductive cells, inherited) and somatic (body cells, not inherited).

1. Germline Mutation: Mutations in reproductive cells (gametes) pass to offspring and occur in every body cell. Hereditary cancer syndromesresult from transmission of damaged genes. For example, BRCA1 and BRCA2 germ-line mutations increase hereditary breast or ovarian cancer risk. Hereditary cancers comprise 10 percent of cases. More than % 50 of human cancers have damaged P53. Germline P53 mutations are rare. P53 is a control gene, so it triggers carcinogenesis; damaged p53 functioning uncontrollably also disrupts other genes.
2. Somatic Mutation: Body-cell damage does not pass to offspring but remains throughout life. Lifestyle (obesity, unprotected sun, smoking, infectious agents) is the major factor. Tobacco, ultraviolet radiation (UV), viruses and aging trigger damage. Cancers arising from it are sporadic, comprising 80 percent of cases.

DNA damage is important because it explains cancer’s origin. Most cancers involve multiple genes interacting with each other and the environment rather than one gene. Better understanding has recently become possible through Epigenetics , studying gene-environment relationships.

Cancer-Driving Mutations Are Identified Through Genetic Tests

In cancer, genetic tests have 2 main purposes:

1. Identify sporadic tumor changes acquired during life rather than inherited, testing suitability for targeted drugs.
2. With family cancer history, identify inherited changes to calculate individual and family risks, support early detection and assess gene-targeted drug suitability. New findings attribute approximately 13 percent of cancers to hereditary mutations.

Different Analytical Methods Exist for Cancer Genetic Tests

• Molecular Genetic Tests: Analyze a gene or DNA segment to identify variants or disease-causing mutations.
• Biochemical Genetic Tests: Measure gene-produced protein quantity or activity to understand DNA changes.
• Chromosomal Genetic Tests: Examine all chromosomes or large DNA regions to detect abnormalities from missing or extra chromosomes.