Genetics - Diseases and Disorders

Some diseases are not caused by problems during cell division, but are thought to have specific genes (or damage to genes) that cause or trigger them.  These genes are present in the parents and are passed down to the children. In this way we say that they are inherited.  These types of diseases run in families.

Genes that code for traits can come in two different forms (alleles).They can either be dominant or recessive.  You receive one allele for each gene from your mom and one from your father.  If you receive two dominant alleles for a trait from your parents, you will have that trait.  If the gene is for a disease, you will have that disease.  

An example of a dominant genetic disease is Huntington's.  Quite a lot is known about the genes involved and we are able to test individuals to see if they have the gene marker.  However, if one of your parents has this gene, you have a 50% chance of getting it passed on to you, and developing the disease.  In the case of this disease you only need to receive the trait from one parent, because the trait is Dominant. 

Recessive genetic diseases can be passed along from generation to generation, but because an individual needs to get the recessive allele from both of the parents, the disease does not show up in them. Examples are cystic fibrosis, albinism, phenylketonuria, galactosemia, and Tay-Sachs disease.  Look at this website to read more about a disease you may be interested in.

Most genetic traits or diseases, however are not caused by a single gene. Remember, some traits appear to be caused by a single gene, but most other traits are caused with a combination of many genes, and environmental factors.