The HCHWA-D disease is hereditary. Maybe you have a general idea of what the disease is, but you would like to know the precise details. Below is a detailed explanation in medical terminology.
HCHWA-D is an autosomal dominant inherited disease, which means that the probability percentage that a child of an affected parent will develop the disease is 50%. To put in other words: if a person who has the disease has a child, there is a 50% chance that this child will also have the disease. This can be explained as follows:
The human body is made up of a large number of cells. These cells contain chromosomes (amongst other things). Chromosomes are the carriers of genetic tendency - for example the colour of your eyes, hair etc. In general each cell contains 46 chromosomes (23 pairs). One pair (of the 23 pairs) consists of the so-called sex chromosomes. A man has one X and one Y chromosome. A woman has two X chromosomes. The remaining 22 pairs contain two identical chromosomes, known as autosomes. These chromosome pairs are numbered from 1 to 22 (based primarily on their size). Thus, the genetic predisposition is present in twofold (with the exception of the hereditary tendency on the X chromosome in males).
In the formation of gametes (egg-and sperm cells) a special division occurs, which causes these cells to contain 23 instead of 46 chromosomes, óne from each pair. During fertilization the fusion of two gametes causes a cell to, once again, contain 2 x 23 = 46 chromosomes. Thus a child receives 23 chromosomes, each from the father and mother.
Chromosomes carry the inheritable predisposition in the form of genes or hereditary factors. A gene determines an inherited trait (for example, the colour of eyes, blood type, etc.). Every human being has about 25,000 different genes and each person has a number of genes that are abnormal, i.e., provide wrong commands. Usually this goes unnoticed as the dysfunction of one gene is compensated for by the action of the same normal gene on the other chromosome of that pair of chromosomes. The gene responsible for the disorder HCHWA-D, is the so-called ß-amyloid gene on chromosome 21.
The inheritance of HCHWA-D is autosomal dominant. Autosomal means that the predisposition to HCHWA -D is not on one of the sex chromosomes, and therefore occurs just as often in boys as in girls. Dominant means that the heritability factor for the disease is stronger than the normal heritability factor (it dominates the normal process). An individual presence of the predisposition is enough to experience symptoms of HCHWA-D.
A person with HCHWA-D can either pass on the normal gene or the gene that carries the disorder. The probability that a child will develop the predisposition for the disease is 50% (1:2).