A few words about Genetic Diseases
One of the most important threats for human’s health is, undoubtedly, the genetic diseases. What a genetic disease is? It is a disorder caused by genetic factors and especially abnormalities in the human genetic material (genome). There are four main types of genetic disorders. Of course, some of these changes in genome can cause interesting advantages in specific environments (Darwinian Fitness). But there is no doubt that all these abnormalities (disorders) bring destructive results to a living being in the present environment.
The four types of (human) Genetic diseases are:
1) Single-gene/monogenic Genetic Diseases:
In this category the starting point is a mutation/change in one gene. The next question is how a change in the sequence of a single gene can cause severe disorders. Genes code for proteins which are some of the most important tools for the living beings, and also take place in the structures of the cells. The results of a mutation that happens in a part of gene that codes for a functional part of a protein are unwelcome. The protein is no more functional and as a result, many severe consequences take place. Almost 6000 single gene disorders are known and it is estimated that 1 of 200 newborns face a single gene genetic disorder. Some of these are sickle cell anemia, cystic fibrosis, Aicardi Syndrome, Huntington’s disease.
2) Multifactorial/Polygonic Genetic Diseases:
The second type of human genetic diseases is caused by mutations in more than one genes. The environment combines with these mutations in order these diseases to appear. We can easily conclude that polygenic disorders are more complicated than the previous type (single gene diseases). These abnormalities are also difficult to analyze, because there are many factors that researchers should take into consideration in order to reach to some useful conclusions. Many well known chronic diseases are Multifactorial Genetic Diseases. Everybody knows Alzheimer, diabetes, obesity and arthritis. Besides many cancer types are caused by multi mutations.
3) Chromosomal Genetic Diseases:
Chromosomes are big DNA molecules composed from genes. The chromosomes are located in the cell nucleus. Abnormalities in the structure, number (and not only) of the chromosomes can cause some of the most dangerous genetic disorders. This type of disorders seem to be much easier to observe because they are, sometimes, detected by examination with microscope. Down Syndrome is the most well known disease caused by chromosomal abnormalities. In this disorder there is a third copy of chromosome 21 (there are two copies of each chromosome in the cells of healthy humans). Chromosomal diseases can be also caused by segments and joins of parts of chromosomes.
4) Mitochondrial Genetic Diseases:
It is not a common situation. Mitochondrial DNA is a DNA molecule found in the mitochondria (out of the nucleous) – a necessary organelle for cellular respiration. Mutations in the mitochondrial DNA can also cause undesirable abnormalities. In the following pages you can find more info about some of the most dangerous human genetic diseases and also reveal the secrets of some rare disorders.