Tay-Sachs disease is an autosomal recessive condition (meaning that it only occurs in individuals that carry two recessive alleles) caused by a mutation at a single locus on chromosome 15. Infants who are homozygous recessive for this disease experience both physical and mental disabilities beginning at six months of age and usually resulting in death by the age of four. 1) The disease is actually very rare, but for this lab, assume that the frequency of the dominant and recessive alleles are equal in your population. Take 50 red beans (representing the dominant allele) and 50 white beans (representing the recessive allele) and put them into a cup. Without looking, draw pairs of beans out of the cup and place each pair together on the table. a) What are the genotype frequencies in your study population? 22% b) Using the Hardy-Weinburg Equilibrium, what proportion of the next generation would you expect to be born with Tay-Sachs disease if none of the assumptions of the model were violated? 2) Because the homozygous recessive condition is fatal early enough in life that no offspring are
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5, and the frequency of the recessive allele (a) is 0.5. According to the Hardy-Weinberg equilibrium, the genotype frequencies in the population can be calculated using the formula: p^2 + 2pq + q^2 = 1 where p is the frequency of the dominant allele (A), q is Show more…
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Tay-Sachs disease is a recessive genetic disease. Individuals with this disease rarely survive past the age of four. In the general population, approximately 1 person in 300 carries the allele for this disease. However, in some populations, including the Irish Americans, the Ashkenazi Jews and the Cajuns from Louisiana, the proportion of Tay-Sachs carriers is much higher (1 in 27 to 1 in 50) than in other populations. Which evolutionary scenario can be predicted to produce a high frequency of Tay-Sachs disease in these populations? Select one: a. All three populations descend from a small number of settlers b. The Tay-Sachs allele is advantageous at the heterozygous state c. These populations experienced disruptive selection d. These populations experienced stabilizing selection e. These populations have higher than average mutation rates
Shaiju T.
Tay-Sachs disease is a severe, autosomal recessive genetic disease that produces deafness, blindness, seizures, and, eventually, death. The disease results from a defect in the HEXA gene, which encodes hexosaminidase A. This enzyme normally degrades $mathrm{G}_{mathrm{M} 2}$ gangliosides. In the absence of hexosaminidase $mathrm{A}$ $mathrm{G}_{mathrm{M} 2}$ gangliosides accumulate in the brain. The results of recent molecular studies showed that the most common mutation causing Tay-Sachs disease is a 4 -bp insertion that produces a downstream premature stop codon. Results of further studies have revealed that the transcription of the HEXA gene is normal in people who have Tay-Sachs disease, but the HEXA mRNA is unstable. Propose a mechanism to account for how a premature stop codon could cause mRNA instability.
Sri K.
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