A mutation is a change in the DNA sequence, the instruction manual for our cells. These alterations can involve removing, adding, or replacing pieces of DNA. While some mutations have no noticeable effect or can even be beneficial, others can lead to harmful outcomes by disrupting normal biological processes.
Mechanisms of Harm: How Mutations Cause Problems
Changes within the DNA sequence can disrupt the normal functioning of genes and the proteins they produce. One way this happens is through altered protein function, where a mutation changes the amino acid sequence that makes up a protein. This can lead to a protein being misfolded, losing its proper shape and ability to perform its task, leading to cellular dysfunction.
Mutations can also occur in DNA regions that control gene expression, such as promoters or enhancers. Alterations in these regulatory sequences can cause a gene to be expressed at the wrong time or in incorrect amounts, disrupting the delicate balance required for cell and organismal health.
Harmful Outcomes: Genetic Disorders and Cancer
Mutations can lead to significant health issues, including genetic disorders and cancer. Genetic disorders are conditions often present from birth, resulting from mutations in an individual’s germline cells that affect nearly every cell in the body. For instance, cystic fibrosis is caused by mutations in the CFTR gene, which produces a protein regulating salt and water movement. When this protein is faulty, it leads to thick, sticky mucus that can clog airways and ducts in various organs.
Sickle cell anemia stems from a mutation in the HBB gene, which provides instructions for making hemoglobin, the oxygen-carrying protein in red blood cells. This mutation causes hemoglobin molecules to clump, distorting red blood cells into a rigid, sickle shape. These cells can then block blood flow in small vessels, leading to pain, organ damage, and anemia.
Cancer primarily arises from the accumulation of acquired mutations in somatic (body) cells over a person’s lifetime. These mutations can occur in specific types of genes that control cell growth and division. For example, mutations in proto-oncogenes can transform them into oncogenes, which act like accelerators, promoting uncontrolled cell proliferation. Conversely, mutations in tumor suppressor genes, which normally act as brakes on cell division, can inactivate them, removing a critical safeguard against abnormal growth. Cancer often involves multiple such mutations working together, leading to the uncontrolled cell growth that defines the disease.
The Source of Harm: Inherited vs. Acquired Mutations
Harmful mutations can originate in two distinct ways: being inherited or acquired. Inherited, or germline, mutations are present in the egg or sperm cells and are passed down from parents to their offspring. Since they originate in these reproductive cells, every cell in the developing individual will carry the mutation from conception. These types of mutations explain why certain genetic conditions run in families and can predispose individuals to specific diseases from birth.
In contrast, acquired, or somatic, mutations occur in body cells after conception. These changes are not present in the reproductive cells and therefore cannot be passed down to future generations. Acquired mutations can arise from errors during DNA replication, the process where cells make copies of their genetic material, or from exposure to environmental factors like ultraviolet (UV) radiation or certain chemicals. They typically affect only the cells and tissues where they arise, and their accumulation over time is a significant factor in the development of diseases like cancer.