Human Chromosomes and Genetic Diseases

In this post, I am going to discuss how genetic diseases are inherited through human chromosomes while investigating some specific diseases. Before we begin, it is important to understand the basics of chromosomes. We have already discussed chromosomes frequently in previous posts, however, we have not yet labeled the specific components as of yet, which is very helpful in understanding genetics.

So how are genetic diseases actually linked to chromosomes? Do better understand this, we are going to look at a specific chromosome (such as the X chromosome shown above) and investigate some diseases attached. 

To begin with, we are going to research Rett Syndrome. This disease is attached to the X chromosome through the mutated gene MeCP2.  It is most common for this mutation to occur on X chromosomes transferred by sperm cells. Rett syndrome is a progressive neurodevelopmental disorder that affect females and very rarely affect males. A possible explanation as to why this disease is rare in males is that males do not inherit the X chromosome from their father, as girls do. As previously stated, most mutated MeCP2 genes are attached to the X chromosome inherited from the father. Rett syndrome occurs in about 1 of 10,000 births and is a common cause of mental impairment. This disease causes multiple symptoms in addition to mental impairment, such as the loss of hand usage ability, reduced muscle tone, seizures, intense eye gaze, and an "autistic-like" phase.    

Another disease we are going to look at is Alport Syndrome, which is also attached to the X chromosome. As MeCP2 was effected in Rett Syndrome, COL4A5 is mutated in order to develop Alport Syndrome. Alport Syndrome is a collagen-related disease affecting the kidneys, ears, and eyes.  Due the fact that the mutated gene associated with Alport Syndrome is passed along with the X chromosome, and the fact that women have two X chromosomes, affected women usually have one normal X chromosome, causing the effects to be much less drastic. This also means that since males only have on X chromosome, affected males will have more severe effects. Symptoms of Alport Syndrome include the breakdown of filters associated with glomerular basement membranes, causing the loss of proteins and red blood cells into the urine. Alport Syndrome also causes progressive deafness and issues regarding the lens of the eyes. 

Resources used for this post are listed below:

http://www.ncbi.nlm.nih.gov/books/NBK22188/

http://www.ncbi.nlm.nih.gov/books/NBK22265/