UCSB Huntingtons and Down Syndrome Autosomal Dominant Diseases Discussion

Comment on the two releases separately

Huntington’s Disease

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Huntington’s disease is an incurable, autosomal dominant disease that causes the degeneration of nerve cells in the brain. The faulty gene is located on chromosome 4, and repeats cytosine, adenine, and guanine (CAG) 36 to 120 times (Brazier)! If one parent has the gene the child has a 50% chance of inheriting the disease, and if both parents have the gene there is a 75% chance their offspring will inherit HD (Nopoulos; Huntington’s Disease Association). Symptoms usually surface in a person’s 30s or 40s, however, 5% of all HD cases are juvenile, meaning they appear before age 20 (Nopoulos). Medications can be taken to help manage the physical, mental, and behavioral symptoms that progress with time, but there is no stopping the individual’s need for full-time care once the disease is at its most severe. While HD alone doesn’t cause death, complications such as choking, pneumonia, and susceptibility to infection from a weakened immune system can be fatal (Brazier). Notable early signs of the disease include mood changes and unusual behavior, and as the loss of control over motor function increases, so do the chances of becoming depressed (Brazier). HD is comparable to dementia, however, those with HD are better are recall than those with dementia making it a key difference between the two (Nopoulos). Those who are 18 and older are able to take a predictive blood test to see if they carry the faulty gene for Huntington’s Disease (Huntington’s Disease Association). 

References:

Brazier, Yvette. “Huntington’s Disease: Symptoms, Causes, and Treatment.” Medical News Today, MediLexicon International, 29 Nov. 2020, www.medicalnewstoday.com/articles/159552

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“Huntington’s Disease Association.” Huntingtons Disease Association, www.hda.org.uk/huntingtons-disease/what-is-hunting…

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Nopoulos, Peggy C. “Huntington Disease: a Single-Gene Degenerative Disorder of the Striatum.” Dialogues in Clinical Neuroscience, Les Laboratoires Servier, Mar. 2016, www.ncbi.nlm.nih.gov/pmc/articles/PMC4826775/

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Down Syndrome is one of the more common genetic disorders that occurs when a sperm and an egg come together to create a cell that contains an extra chromosome. Therefore instead of having 46 chromosomes, patients with down syndrome have 47. According to MedicineNet around 95% of these patients have an extra chromosome 21, which accounts for the physical malformations that occur (Wedro, 2020). In terms of physical appearance, down syndrome looks like a flattened face, small neck, shorter stature, and smaller features such as ears, hands, feet, etc., and in terms of mental capabilities those with down syndrome tend to have lower IQs than the average person (CDC, 2021). The three types of Down Syndrome that exist are Trisomy 21 where patients have three separate copies of chromosome 21, Translocation Down Syndrome where patients have an extra chromosome 21 that is attached to another chromosome, and Mosaic Down Syndrome where some of the patients cells have two copies of chromosome 21 and some have three (CDC, 2021). Although there is no exact cause for this genetic mutation, it has been found that women who have babies at a later age are more at risk of delivering a baby with down syndrome. According to gynecologist Dr. Horsager-Boehrer at the UT Southwestern Medical Center, the connection between older maternal age and down syndrome is that as we age we have lower levels of proteins called cohesin and securin that keep our chromosomes together, therefore lower levels of these proteins makes it easier for chromosomes to not split up properly during mitosis/meiosis (Horsager-Boehrer, 2017). 

References: 

Benjamin Wedro, MD. “Down Syndrome Causes, Symptoms, Facts & Prevention.” MedicineNet, 10 Nov. 2020, www.medicinenet.com/down_syndrome_overview/article.htm.

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“Facts about Down Syndrome.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 6 Apr. 2021, www.cdc.gov/ncbddd/birthdefects/downsyndrome.html#ref.

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Horsager-Boehrer, Robyn. “Why Does a Woman’s Age Impact the Risk of Down Syndrome in Her Baby?: Your Pregnancy Matters: UT Southwestern Medical Center.” Your Pregnancy Matters | UT Southwestern Medical Center, 6 June 2017, https://utswmed.org/medblog/age-matters-down-syndr…

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