GeneticsGenetic inheritance



The chromosomes contain the genes you inherit from your parents.





  • what genes they inherit
  • whether the gene for that condition is dominant or recessive
  • their environment, including any preventative treatment they may receive

Genetic mutations





Mutations can have 3 different effects. They may:

  • be neutral and have no effect
  • improve a protein and be beneficial

Passing on mutations


Depending on the specific condition concerned, these genetic conditions can be inherited in 3 main ways, outlined below.

Autosomal recessive inheritance


If the child only inherits 1 copy of the faulty gene, they'll be a carrier of the condition but won't have the condition.

If a mother and a father both carry the faulty gene, there's a 1 in 4 (25%) chance of each child they have inheriting the genetic condition, and a 1 in 2 chance (50%) of their child being a carrier.

Examples of genetic conditions inherited in this way include:


Autosomal dominant inheritance

Some conditions are inherited in an autosomal dominant pattern. In this case, only 1 parent needs to carry the mutation for the condition to be passed on to the child.

If 1 parent has the mutation, there's a 1 in 2 (50%) chance it will be passed on to each child the couple has.

Examples of genetic conditions inherited in this way include:

X-linked inheritance

Some conditions are caused by a mutation on the X chromosome (1 of the sex chromosomes). These are usually inherited in a recessive pattern, but in a slightly different way from the autosomal recessive pattern described above.

X-linked recessive conditions often do not affect females to a significant degree because they have 2 X chromosomes, 1 of which will almost certainly be normal and can usually compensate for the mutated chromosome. However, females who inherit the mutation will become carriers.

Males cannot inherit X-linked mutations from their fathers because they receive a Y chromosome from them. A male will develop the condition if he inherits the mutation from his mother. This is because he does not have the normal X chromosome to compensate.

When a mother is a carrier of an X-linked mutation, each daughter they have has a 1 in 2 (50%) chance of becoming a carrier, and each son they have has a 1 in 2 (50%) chance of inheriting the condition.

When a father has an X-linked condition, his sons will not be affected because he'll pass on a Y chromosome to them. However, any daughters he has will become carriers of the mutation.

Examples of genetic conditions inherited in this way include:

  • haemophilia – a condition that affects the blood's ability to clot

New mutations

Although genetic conditions are often inherited, this is not always the case.





Chromosomal conditions


Examples of conditions caused by chromosomal abnormalities include:


Influence of the environment










Page last reviewed: 13/10/2016
Next review due: 13/10/2019