Diseases which are transmitted by sex linked inheritance have the gene for the condition on the X chromosome.
A chromosome is just a package of codes for different tissues of the body, perhaps in the same way that one volume of the Encyclopaedia Britannica contains some information from the whole encyclopaedia in a conveniently sized bundle. The human body has two copies of each chromosome, one from each parent. There are 23 pairs of chromosomes. One pair determines whether a person is male or female. This pair is made up of ‘X’ and ‘Y’ chromosomes. If someone is ‘XX’, they are female. If someone is ‘XY’, they are male. The ‘Y’ chromosome is smaller than the ‘X’ chromosome, and it so happens that the alpha-galactosidase gene is missing from the ‘Y’ chromosome. Therefore, if a male has a defective alpha-galactosidase gene, there is no normal copy to produce normal enzyme.
A woman has two ‘X’ chromosomes. If one is abnormal, there is a second copy which produces effective levels of alpha-galactosidase.
NKF Controlled Document No. 42, Sex Linked Inheritance, written 23 November 2002. Last reviewed 29 November 2012.
The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.