Misconceptions about genetics

Misconceptions about genetics

General practitioners (GPs) can use the information below to address common misconceptions about genetic issues during discussion with patients.

Information for patients



If your father has a genetic condition, but you look more like your mother, you will not develop it

An individual’s physical similarity to other relatives (or lack thereof) does not affect their risk of developing a condition

You can only inherit a ‘female’ cancer like breast or ovarian cancer from your mother’s side

Gene variants in BRCA1 and BRCA2 can be passed through the paternal line (a person’s father and his relatives) and maternal line (a person’s mother and her relatives)

If you have gene for a particular disease, you will eventually get the disease

The presence of a pathogenetic variant does not always mean an individual will develop the condition. If the gene variant shows variable penetrance (ie less than 100% of people with that gene variant manifest the condition), the risk of disease can be uncertain

A ‘one-in-four’ chance of having a child with the variant means that after you have one affected child, the next three children will be unaffected

A ‘one-in-four’ chance of having a child with the variant applies to each pregnancy (for autosomal recessive conditions)

Female carriers of X-linked conditions are never affected

This is not always the case and is influenced by X-inactivation. Carriers may have a mild phenotype and are manifesting heterozygotes. For example, female carriers of Duchenne muscular dystrophy may show mild symptoms of a cardiomyopathy; female carriers of haemophilia may have a bleeding diathesis

If you have no family history of a genetic condition, you are not at risk of developing one and neither are your children

There may be no family history for a variety of reasons. For example, reduced or incomplete penetrance, recessive conditions, small family size, and new mutations (eg de novo, sporadic)

Genetic conditions can ‘skip’ a generation

In the case of autosomal recessive and X-linked conditions, affected family members may be scattered across a generation, giving the appearance of skipping generations