Spotlight on Gene Mutations: 8 Facts You Need to Know

A gene mutation is a permanent alteration in a sequence of DNA, rendering it different from that found in most people. What causes gene mutations, and how can they impact our health? We look at the facts.

1. Gene mutations can occur on a small or large-scale.

Gene mutations can take various forms. Small-scale mutations include the following:

· Point mutation — an alteration in one base in a DNA sequence.

· Substitution — the substitution of a DNA base.

· Inversion — the reversal of the chromosome’s DNA sequence.

· Insertion — the addition of a base to the DNA sequence.

· Deletion — the deletion of a DNA base.

Large-scale gene mutations can affect whole genes or chromosomes. Examples of large-scale gene mutations include the following:

· Copy number variations featuring repetition, insertion, or loss of large sequences of DNA. These types of gene mutations can affect up to 5 million bases.

· Deletions of large areas of the chromosome.

· Duplication of genes.

· Loss of one or both gene copies.

· Migration of DNA sequences from one location to another.

· The addition of an extra chromosome.

2. Some gene mutations can arise during a person’s lifetime.

There are two distinct categories of genetic mutation: hereditary and somatic. Hereditary gene mutations pass from parent to child at conception. All of our genes are contained within the genome: a complete set of instructions for making the human body. Where a person inherits a gene mutation, it comprises part of their genome, a copy of which can be found in virtually every cell of the human body. Some hereditary gene mutations directly cause disease, whereas others make us more susceptible to developing a particular disease in our lifetime. People who carry genetic mutations may not inherit the associated disorder, but could pass a faulty gene copy on to their own children, who may also develop the associated condition.

Somatic gene mutations occur spontaneously rather than being passed on by our parents. They are acquired during a person’s lifetime and are usually limited to certain cells rather than being found in every cell of the body.

Somatic gene mutations can occur spontaneously in early embryonic development or much later during an individual’s lifetime. A range of environmental factors can trigger somatic gene mutations, such as UV radiation from excessive sun exposure or contact with hazardous chemicals.

3. Not all gene mutations are harmful.

In fact, only a small percentage of gene mutations cause genetic disease. Most gene mutations have little to no impact in terms of our health, and indeed, many confer positive traits. Scientists view gene mutations as an intrinsic part of the evolutionary process, helping humankind to adapt to environmental changes, facilitating our migration across a diverse range of habitats over several thousand years.

4. Scientists estimate each of our genomes features around 60 gene mutations.

These dictate the way that we look and the way our bodies function. A few gene mutations can make us more susceptible to disease.

5. Mary-Claire King discovered the cancer-causing gene BRCA1

Mary-Claire King, then a professor of medicine and genome sciences at the University of Washington, discovered BRCA1, the first gene linked to ovarian and breast cancer, in 1990. Today, BRCA1 and BRCA2 testing help to diagnose up to 25% of inherited breast cancer cases in the United States, providing medical practitioners with vital insight into their patients’ unique genetic makeup, enabling them to steer countless women toward potentially life-saving treatments.

6. You can carry a gene mutation without developing the associated disease.

Some gene mutations cause disease that is present and apparent at birth. Other gene mutations do not directly cause disease, but may increase your chances of developing disease during your lifetime.

Approximately 12% of the US female population will develop breast cancer during their lifetime. An estimated 72% of women who test positive for the BRCA1 mutation will develop breast cancer by 80 years of age, compared with 69% of BRCA2 carriers. Both mutations are genetic “markers” indicating that a woman has an increased risk of developing breast cancer during her lifetime. While screening can reveal a genetic predisposition, a positive test result does not guarantee the individual will ever develop the disease.

7. Genetic carrier screening plays a vital role in family planning.

Some people who carry a gene mutation may have a strong family history of the associated disorder, but because the majority of genetic disorders are recessive in nature, they can arise quite unexpectedly. Therefore, healthcare providers around the world regard genetic carrier screening as a vital step in starting a family.

Genetic carrier screening can test for the mutations associated with cystic fibrosis, spinal muscular atrophy, fragile X syndrome, sickle cell anemia, Tay-Sachs disease, and a range of other hereditary disorders.

The American College of Obstetricians and Gynecologists advocates for carrier screening as a fundamental step in family planning for all women, regardless of their family history or ethnicity. The only way to definitively find out whether or not you carry a gene mutation associated with a genetic disease is through carrier screening.

8. Carrier screening can prove beneficial in regards to disease treatment.

No matter your family history, undergoing genetic carrier screening is part of a proactive approach to starting a family. Genetic carrier screening provides your doctors and healthcare professionals with insight into your unique genetic makeup, which is invaluable in family planning and can also be beneficial in terms of disease treatment and prevention.