Week 9 - Genetic Disorders

Genetic disorders are obtained through inheritance, whether they are autosomal, sex-linked, dominant, or recessive. Autosomal disorders are a result of gene mutations within the first twenty two chromosomes, while sex-linked disorders result from mutations within the twenty third (sex) chromosome. Ever since my freshman year of high school, I have been deeply fascinated by genetics in general, but learning about inherited diseases has been even more intriguing.

For example, Queen Victoria was a carrier for Hemophilia, a medical condition in which the ability for blood to clot is significantly reduced. Although she was a carrier for Hemophilia, her phenotype did not express the trait. In other words, Victoria was heterozygous for Hemophilia, thus showing that Hemophilia is a recessive disorder. If you were to study a pedigree of Victoria's family, you would see that some of her daughters were likewise carriers of Hemophilia; however, each of her sons who obtained the Hemophilia gene were homozygous recessive (they carried AND expressed Hemophilia traits). Based off of this scenario, you can infer that Hemophilia is a sex-linked recessive disorder. Only the recessive alleles carry hemophilia—since girls are given an x allele by each of their parents, girls typically are only carriers of the disease, being that one x may be affected while the other x is normal. Boys, on the other hand, are at much greater risk for expressing Hemophilia. Since boys are only given one x, they must either show full-blown symptoms of Hemophilia or not have it at all.

Although recessive disorders are most common, there are still dominant disorders out there, such as Huntington's disease. This disease is autosomal dominant and involves the deterioration of brain cells between a person's 30's and 40's. Death is a common result of Huntington's, but it continues to be passed down from generation to generation, due to the fact that most Huntington's victims are able to reproduce before they are affected. Children who are either heterozygous or homozygous dominant for Huntington's WILL obtain it, whether they are a boy or a girl. The children who are homozygous recessive for the trait, however, are safe and will not obtain Huntington's.

As I take more and more biology classes, I continue to gain a better understanding of these kinds of genetic disorders. My affinity for this topic is currently influencing what my major will end up being—I have declared Biology for right now, but I am also seriously considering Genetics for a major. I personally believe that advanced studies toward genetic disorders will, in turn, benefit the members of our society who have predetermined genetic diseases, being that these studies might help scientists, geneticists, and doctors come up with solutions to inevitable disorders.