Answered: A possible explanation for the…

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter11: Genome Alterations: Mutation And Epigenetics

Section: Chapter Questions

Problem 16QP: Familial retinoblastoma, a rare autosomal dominant defect, arose in a large family that had no prior...

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Tay Sachs is a rare autosomal recessive disorder that causes mental and physical disabilities leading to death in infants. Affected individuals are lacking the enzyme hexosaminidase, causing lipids to build up in the brain.

The HEXA gene on chromosome 15 codes for hexosaminidase, and a four base pair insertion in the gene results in an altered reading frame and non-functional enzyme being produced. Individuals who are carriers (heterozygotes) of the Tay-Sachs allele are not affected by the disease but appear to have increased protection against tuberculosis.

The incidence of Tay-Sachs disease is much higher among Ashkenazi Jews originating from Eastern Europe than the general population of the United States. About 1 in 3 500 babies of Ashkenazi Jewish heritage are born with Tay-Sachs disease and about 1 in 30 Ashkenazi Jews are carriers compared to about 1 in 320 000 babies born with the disease and about 1 in 300 carriers in the general United States population. Ashkenazi Jews living in Europe at the turn of the century often lived in urban areas with a high incidence of tuberculosis.

A possible explanation for the increased incidence of Tay-Sachs disease among Ashkenazi Jews is

a. Ashkenazi Jews are genetically predisposed to carry the Tay-Sachs allele

b. overcrowding predisposed Ashkenazi Jews to an increased chance of Tay-Sachs disease

c. the prevalence of tuberculosis in Eastern Europe provided a selective advantage to individuals who were heterozygous for the Tay-Sachs allele

d. infection with tuberculosis provided a selective disadvantage to individuals who were heterozygous for

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