Tay-Sachs Disease Case Study

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Register to read the introduction… This disorder also displays a pattern of complete penetrance when individuals are homozygous for the recessive allele18. On average, patients that acquire the infantile-onset form of this disorder begin displaying symptoms within the first five months of life and most die by the age of four from neurological degeneration complications17,24. The phenotypic features of infantile-onset Tay-Sachs disease include a red spot on the retina of the eye, low muscle tone, being easily startled, increased sensitivity to sound, decline in mental and physical development, apoptosis of the neurons in the central nervous system causing vacuoles in the brain, cardiac rhythm abnormalities, and 98% developed …show more content…
The general population prevalence is 1 in 200,000 births, while the Ashkenazi Jewish population experiences a prevalence of TSD in 1 in 2,500 to 3,900 births16. Members of high-risk populations should be aware of their carrier status before conceiving. Due to the autosomal recessive pattern of inheritance both parents must carriers, in which case their offspring have a 1 in 4 risk of developing the disorder (Figure 1).
Questions for Small Group Discussion
1. Why is there a greater prevalence of TSD in populations like the Ashkenazi Jews?
There are a few possible explanations as to why there is a higher prevalence of TSD among the Ashkenazi Jews. They are culturally isolated, in that many of this population choose to marry and have children with others from within their community. This small population is more susceptible to the effects of genetic drift on allelic frequency. Another explanation employs the theory of the Founder effect. This theory states that when a population is started from only a few individuals, the number of allele variables available for each gene is quite limited. If there were carriers present in the founding population then its prevalence will be magnified in the growing population
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Individuals that are heterozygous exist in the population without demonstrating any signs or symptoms of the disorder. They can then silently be passing their mutant allele on to future generations, creating more carriers. When two TSD carriers conceive, the offspring have a ¼ chance of being affected and having TSD.
3. How have screening programs been able to have such an impact on TSD?
Screening programs, especially those targeted at high-risk populations, have been a large educational component in the quest to decrease the prevalence of TSD. By informing individuals of their status regarding Tay-Sachs, be it as a carrier or safe and sound, they are better able to understand the risks associated with passing their particular genes on to the next generation. It can assist couples to better plan for the growth of healthy, TSD free families, by providing genetic counseling and/or exploring alternatives to conventional conception.
4. Is there only one single mutation associated with TSD? How is it possible that more than one mutation can cause the

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