2 February 2014
Dominant or Recessive
All the genes possessed by an individual constitute its genotype. The phenotype is the result of gene products brought to expression in a given environment. Whenever one pair of alleles can come to phenotype expression only in a homozygous genotype, we call that allele a recessive factor. The allele that can phenotypically express itself in the heterozygote as well as in the homozygote is called a dominant factor. (Stansfield 37). From these different factors there are different birth defects that can occur. For instance, to get sickle cell anemia, a child must receive two copies of the mutant gene. This disease is a recessive trait. Other genetic diseases are dominantly inherited. This paper will address Huntington's disease which is a dominantly inherited genetic disease.
The disease that caused the death of folk singer Woody Guthrie in 1967 is called Huntington disease. Named for George Huntington, the physician who first described the illness in 1872, Huntington disease used to be known as Huntington's chorea, from the Greek word for choreography or dance. The name refers to the involuntary, jerky movements that can develop in later stages of the illness. Huntington's disease affects someone's ability to think, talk, and move by destroying the cells in the basal ganglia. It causes a degeneration of the nervous system and normally suffers usually do not develop the disease until they are in their 30s or 40s.
This mutation stems from inserted DNA, which disrupts the function of the normal gene. There are copies of the nucleotide sequence CAG repeated over and over again. Although this sequence occurs in a normal person's genes 10,20,30 times. Huntington's patients have the CAG sequence repeated from 40 to 100 times, and the # of repeats increases with each generation. This increase means that the son or daughter who inherits this disease will have more CAG repeats than their father or...