Disorders in Human. Sex-linked inheritance In humans, there are hundreds of genes located on the X chromosome that have no counterpart on the Y chromosome. In criss-cross inheritance, an X-linked recessive gene is transmitted from P1 male parent father to F2 male progeny grandsons through its F1 heterozygous females daughterswhich are called carriers and different F1 and F2 results ratios in the reciprocal crosses.
The table lists some sex-linked conditions. Human genetic disease. Thank you for your feedback.
In general, it can be said that risks of recurrence are not as great for multifactorial conditions as for single-gene diseases and that the risks vary with the number of relatives affected and the closeness of their relationship.
Article Media. Although disorders resulting from single-gene defects that demonstrate Mendelian inheritance are perhaps better understood, it is now clear that a significant number of single-gene diseases also exhibit distinctly non-Mendelian patterns of inheritance.
The table lists some sex-linked conditions. Inheritance of Y-Linked Genes. These cases are now known to result from uniparental disomya phenomenon whereby a child is conceived who carries the normal complement of chromosomes but who has inherited both copies of a given chromosome from the same parent, rather than one from each parent, as is the normal fashion.
Inheritance of Y-Linked Genes. If the maternally inherited copy carries a mutation, the child again will be left with no functional copies of the gene expressed, and the clinical traits of Angelman syndrome will result. Indeed, improvements in the tools used to study this class of disorders have enabled the assignment of specific contributing gene loci to a number of common traits and disorders.
Genetic imprinting involves a sex-specific process of chemical modification to the imprinted genes, so that they are expressed unequally, depending on the sex of the parent of origin. Another example includes hereditary enamel hypoplasia hypoplastic amelogenesis imperfecta , in which tooth enamel is abnormally thin so that teeth appear small and wear rapidly down to the gums.
So-called maternally imprinted genes are generally expressed only when inherited from the father, and so-called paternally imprinted genes are generally expressed only when inherited from the mother.