What Is Autosomal Dominant Genes?

Autosomal dominant inheritance refers to a genetic disease in which the defective gene is dominantly expressed, and 50% of children have the possibility of developing the disease. The role of genes can be influenced by the environment and other genes that alter their phenotypic expression (expression). Therefore, even within the same family, people with the same genetic alteration (allele) can exhibit very different phenotypes. For example, in Waardenburg syndrome type I, PAX3 gene mutations typically result in white hair on the forehead, widening eye distance, and heterochromia, but less than 20% of cases have severe hearing loss.

Autosomal dominant inheritance

Autosomal dominant inheritance refers to a genetic disease in which the defective gene is dominantly expressed, and 50% of children have the possibility of developing the disease. The role of genes can be influenced by the environment and other genes that alter their phenotypic expression (expression). Therefore, even within the same family, people with the same genetic alteration (allele) can exhibit very different phenotypes. E.g

Some family members with abnormal alleles show no signs other than white hair on the front part. However, their children may have severe congenital deafness due to the same mutation. Rarely, the performance is very low without clinical abnormalities However, he can pass the abnormal allele to the offspring to produce all the clinical symptoms. In this case, there can be a generation of gaps in the genealogy. This phenomenon is called penetrance loss. However, some penetrances are missing The condition is caused by the examiner's failure to identify or be unfamiliar with the mild manifestations of the genetic disease. Cases with low manifestations are sometimes considered to be free-running.

A single gene defect can cause multiple abnormalities in different organ systems.

Features that are only found in a certain sex are called restricted inheritance. This is different from X-linked inheritance, which means that the genetic characteristics are carried by the X chromosome. Sex hormones and other physiological differences between men and women can affect the expression of genes. For example, early Baldness is an autosomal dominant feature, but it may be related to estrogen, so it is rarely expressed in women and often only occurs after menopause. Therefore, the limited inheritance may be more accurately called the sexual influence inheritance, which has a limited degree of expression And a special case of penetrance.

A mutation is a spontaneous change in genetic information. An autosomal dominant genealogy begins with a new mutation and changes in genetic information (DNA) passed down from the parent. The incidence of mutations in known autosomal dominant genetic diseases is It's different (from 6,000 to 50,000).

For example, about 80% of cartilage hypoplasia dwarfism (genus autosomal dominant inheritance) has no family history and is a new mutation. Almost all patients can pass the newly mutated gene to their offspring. In cartilage hypoplasia, mutations occur At a very specific location in a gene. In many other conditions, new mutations can occur at different locations in the gene.

Normally, non-affected parents are not at greater risk of having sick children. But some parents with normal appearance can have two or even three children with typical cartilage dysplasia dwarfism. The cause is germ cells The lineage is mutated, that is, early in the development of the embryo of a normal-looking parent, when there are only a few precursors of germ cells. Newly mutated cells provide many cells to the developing gonad. In this case The chance of giving birth to another child is as high as 50%. Molecular genetic studies of genetic mutations between parents and children have confirmed mutations in this germ cell line. In fathers with normal phenotypes who carry mutations in germ cell lines Molecular biology studies have confirmed that many of its sperm carry mutations.