Who carries the gene for hypertrophic cardiomyopathy the mother or the father or both?

Answer 1

The short answer is that, for a girl, both the mother and the father are the source of the genes which she inherits.

For a boy, his sex-related genes are carried by the Y chromosome which he inherits from his father and his mother is the source of the genes which are carried in his X chromosome. Both his mother and his father are the source of his non-sex-related genes.

A longer answer

Several different causes of the medical heart condition that is called hypertrophic cardiomyopathy (HCM) are possible. A patient who has been identified as having HCM means that investigations using various forms of testing have shown that some of the muscular membranes of the patient's heart have grown to be thicker than normal.

Such a change is called a mutation. The vast majority of mutations are not on the sex chromosomes (X and Y) - none are on the Y and <4% are on the X - so we can ignore Y linked inheritance as a cause. *** (See Note below.)

Basically the gene change can come from the mother or the father but can also start spontaneously in an individual. All conditions have to start somewhere and on very rare occasions both parents can have mutations. If a child was to inherit gene changes from both of its parents it would generally have a lot of problems at an earlier age.

When an individual has more than one mutation it makes things a lot more complicated to explain.

Generally the cause is what is called dominant inheritance, meaning that it is not linked to the X or Y chromosomes which determine sex. This is where the mother or the father has a mutation on one of the non-sex-related genes which are known to produce HCM. They also will have another copy of the same gene because one copy comes from their mother and one from the father. They pass on one copy of their gene to each child (either 'good' or 'bad') so with each child there is a 50:50 or 1 in 2 chance of the child inheriting the 'good' or the 'bad' copy.

A mother will pass on one of her X chromosomes to her child and a man will pass on either his X (producing a daughter) or his Y (producing a son). If a woman has a mutation on one of her X chromosomes there is a 50:50 or 1 in 2 chance she will pass it on to each child (boy or girl). If a man has a mutation on his X chromosome he will always pass on the condition to his daughter but never to his son.

As the daughter has another X chromosome this can compensate for the mutation, often meaning such a female child will display little if any signs of the condition. Such a female is called a carrier and, in turn, there is a 50:50 risk of her passing it on to any child.

Medical genetics research has identified not just one gene but several genes which, if mutations are present, can cause HCM. Different combinations of these mutated genes cause different forms and degrees of seriousness of the disease.

The resulting consequences to good health may be mild or severe depending on the actual combination of mutated genes which are present.

Some combinations of the mutated genes which can produce HCM can also produce malformations in other organs which may have mild or severe consequences. Some examples of other affected organs are the kidneys, causing renal illnesses, and/or the skin, causing dermatological illnesses.

*** Note: Any female possesses two X sex chromosomes and a male possesses an X and a Y.