In my Biology class, I have been learning about different genetic disorders. One that has caught my interest is Huntington’s disease because research shows that there may be an evolutionary advantage to having this debilitating disease.
Huntington’s disease results in progressive degeneration of neurons in the brain, caused by a change in the HTT gene, which makes a protein called huntingtin. The deformity in the HTT gene is an excess of CAG nucleotide repeats in the genetic code.
Generally, symptoms start to set in around the age of 35-44 years old. Symptoms come in stages. In the early stage, some examples are depression, abnormal eye movements, and paranoia. In the middle stage, some examples are speech difficulties, weight loss, and slow reaction time. In the final stage, some examples are the inability to speak, walk, and care for themselves. Patients that are diagnosed with Huntington’s normally live 15-20 years after diagnosis. (Genetic and Rare Diseases Information Center, 2018).
Huntington’s disease is an autosomal dominant trait. This means that a person only needs one copy of the mutated gene in order to have the disorder. Therefore, a parent with Huntington’s disease can either pass on the dominant mutated gene which results in the child having Huntington’s disease, or they can pass on the recessive healthy gene which results in the child not having Huntington’s disease. This means that there is a 50% chance that each child will inherit Huntington’s disease (Mayo Clinic, 2020).
If Huntington’s disease is so deadly, why would it be so relatively pervasive? This may be because the mutated HTT gene provides an evolutionary advantage by making you healthier during your childbearing years, allowing you to produce more offspring. This compounds the fact that its symptoms don’t take effect until after you have had children. Therefore, the onset of the disease does not have an evolutionary disadvantage (Science Daily, 2007).
“Huntington Disease.” Genetic and Rare Diseases Information Center, U.S. Department of Health and Human Services, https://rarediseases.info.nih.gov/diseases/6677/huntington-disease.
“Huntington’s Disease.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 14 Apr. 2020, https://www.mayoclinic.org/diseases-conditions/huntingtons-disease/symptoms-causes/syc-20356117#:~:text=Huntington’s%20disease%20is%20an%20autosomal,one%20copy%20from%20each%20parent.
“Biologists Link Huntington’s Disease to Health Benefits in Young.” ScienceDaily, ScienceDaily, 26 Sept. 2007, https://www.sciencedaily.com/releases/2007/09/070925130029.htm
Evolutionary Anthropology 