WHAT IS MUTATION AND WHAT CAUSES A MUTATION?

A mutation refers to a permanent change in the DNA sequence that makes up a gene. Mutations can lead to the production of abnormal proteins, incapable of performing their functions correctly, which subsequently affects the normal functioning of the cells. Even a small change in the DNA sequence–as simple as changing a single DNA protein in the rung of the DNA ladder–can affect the functions of a protein, negatively affecting the cell. Luckily, cells have designated proteins that can repair most mutations. However, sometimes the repair processes fail. Mutations in genes that control cell division or cell death can cause uncontrolled cell growth and division, leading to cancer.
 

What causes a mutation?

Mutations can have several underlying causes, including biological causes, mutagens, and lifestyle.

1. Biological: Biological changes to DNA can occur through errors in DNA replication, may happen spontaneously, or result from aging.
• Errors during DNA replication: DNA replication is a highly regulated process, but the process is still prone to errors. For example, when an incorrect base (A, T, G, or C) becomes part of the DNA during replication, changes in the DNA sequence can result. Sequencing errors affect the gene and can lead to the formation of an incorrect protein with impaired function. Despite having DNA repair mechanisms, an error can lead to escape from repair, passing along the mutation every time the cell divides.
• Spontaneous mutations: Mutations can occur spontaneously in the DNA because of natural biochemical reactions occurring within the cell. For instance, cellular metabolism results in the production of reactive oxygen species (ROS) such as superoxide radicals (O2•), hydrogen peroxide (H2O2), and hydroxyl radicals (OH•). ROS can cause damage to DNA and change its structure or sequence, leading to mutation.
• Aging: Aging affects the DNA repair process and makes it less efficient, causing the accumulation of damaged and mutated DNA, leading to cancer.
2. Mutagens: Mutagens are physical, chemical, or biological substances that can interact with DNA to facilitate changes in its sequence and structure. Mutagens that increase the risk of cancer are carcinogens. Types of mutagens include the following:
• Physical mutagens: Ionizing radiation, such as ultraviolet (UV) rays, gamma rays, or X-rays cause DNA damage by breaking DNA strands, fusing DNA bases, or generating ROS. Damage caused by physical mutagens can alter the DNA structure, sequence, and repair mechanisms, possibly leading to mutation.
• Chemical mutagens: Compounds, such as those found in cigarette smoke, can react with DNA bases and change their chemical structure through different mechanisms. Chemical mutagens can also include base analogs which substitute for DNA bases during replication, molecules that may insert between bases in DNA, or heavy metals (arsenic, lead, cadmium, chromium, and nickel).
• Biological mutagens: Viruses may insert genetic material into the host’s genome to cause mutation, which could disrupt the normal genetic function of the gene. Certain bacteria can cause oxidative damage in the cells, leading to the formation of ROS, damaging DNA and reducing the efficiency of DNA repair systems, collectively increasing the risk of mutations.
3. Lifestyle factors: As mentioned above, tobacco contains mutagenic compounds that can cause DNA damage. Persistent exposure or exposure to high levels of these substances may increase the risk of developing cancer. Time in the sun can also be damaging because exposure to UV rays can cause mutations in the DNA of skin cells, leading to skin cancer.

Understanding what factors may lead to mutations can help you determine how best to protect your pet from these causes, and work towards a cancer-free life for your furry friend.