Inherited childhood conditions

Parents pass on traits or distinguishing characteristics such as eye and hair colour to their children through their genes. Many health conditions and diseases are also genetic. Genes may also influence some behavioural characteristics, such as intelligence and natural talents. An allele, is one of a number of alternative forms of the same gene. It is the alternative form of a gene for a character producing different effects. Dominant inheritance is when one allele of a gene is dominant within the pair. For blood groups, the A allele is dominant over the O allele, so a person with one A allele and one O allele has the blood group AO. So a child may have blood group A because the blood group A gene inherited from their mother is dominant over the blood group O gene inherited from their father.

Not all genes are either dominant or recessive. Sometimes, each allele in the gene pair carries equal weight and will show up as a combined physical characteristic. For example, with blood groups, if the A allele is as ‘strong’ as the B allele, the blood group AB. Many cultures approve of marriage between relatives such as first cousins. A relationship between related people is called consanguinity. Related parents are more likely than unrelated ones to have children with health problems or genetic disorders. If both partners carry the same inherited altered (mutated) gene, their children are more likely to have a genetic disorder. If two parents have a copy of the same altered gene, they may both pass their copy of this to a child. In this case the child receives both altered copies. As the child then does not have a normal, functioning copy of the gene, she will develop the disorder. This is called autosomal recessive inheritance. The parents are ‘carriers’ of the genetic condition but are unaffected themselves. Autosomal recessive genetic disorders are more likely if two parents are related, although they are still quite rare. Examples of autosomal recessive genetic disorders include sickle cell disease and albinism.