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Autosomal recessive inheritance

In this video, we will learn that autosomal recessive inheritance, where an affected individual has a mutation in both gene pairs.
In autosomal recessive inheritance, an affected individual has a mutation in both copies of a gene pair. Where an individual only has one mutation in the pair, they are unaffected and are a carrier for the condition. Those parents who are carriers for an autosomal recessive condition have a 25%, or one in four chance of a child inheriting both mutated gene copies and being affected, a 50% chance of a child inheriting only one mutated copy and being a healthy carrier like the parents, and a 25% chance of the child inheriting neither mutated copy and being unaffected.
The things that might make you suspect an autosomal recessive condition in the family are that males and females have the condition in roughly equal proportions, and that people with the condition are usually in one sibship in one generation. In addition, autosomal recessive conditions are more common amongst consanguineous families, where both parents have one or more ancestors in common. The commonest autosomal recessive condition in northern Europe is cystic fibrosis, with an incidence of around one in 2,500. Around one in 25 Caucasians are carriers. Cystic fibrosis is a disorder of the secretory glands that primarily affects their lungs and digestive tract.
While treatment is improving all the time for patients with CF, lung function often starts to decline in early childhood and respiratory failure remains the most common cause of death in people who have CF.

In this video, we learnt about autosomal recessive inheritance, where an affected individual has a mutation in both genes of a pair.

If an individual has a mutation in only one gene of a pair, they are a healthy carrier of the condition.

Autosomal recessive inheritance may be suspected within a family if:

  • Both males and females are affected in roughly equal proportions.
  • Individuals affected with the condition are in one sibship in one generation.

Autosomal recessive genetic conditions, whilst still rare, are more likely to occur in consanguineous families where both parents have at least one ancestor in common.

An pedigree depicting autosomal recessive inheritance An example family pedigree depicting autosomal recessive inheritance Click to expand
© St George’s, University of London

Talking point

The most common autosomal recessive condition in Northern Europe is cystic fibrosis; a disorder that results in abnormally thick mucus secretions that primarily affects the lungs and digestive tract.

Do you know of other autosomal recessive conditions that are particularly prevalent in other ethnic groups?

Do you want to know more?

The Cystic Fibrosis Foundation video Adding Tomorrows gives an insight into how people cope with, and manage from a young age, diseases which affect life and life expectancy.

© Images of Cystic fibrosis and Meconium ileus courtesy of Wellcome Images

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