Is HD gene on the X chromosome?

Q. Father inherited HD from his mother. Therefore, will everyone of his female offspring inherit the HD gene due to the ‘X’ chromosome contributed by the father, making probability 100% vs. 50%?

MJ, Young Adult, USA

A. Hi MJ,

Thanks very much for sending a question about how HD is passed on in families. The HD gene is actually not on the X-chromosome (it’s on Chromosome no 4) and so the risks are the same for males and females. Therefore in the example you gave of a father inheriting HD from his mother, each child, whether male or female, will have a 50% risk of inheriting the condition (or to put it another way an equal chance of not inheriting the condition). Do you have a family history of HD MJ? If so, & you would like to ask more questions, do email again.

All the best,

Rhona