Tay Sachs is a lysosomal storage disease that is inherited in an autosomal recessive manner (T= dominant allele; t = recessive allele). Individuals with Tay Sachs have a defect in the gene encoding hexosaminidase A, a lysosomal enzyme that breaks down cell membrane components called gangliosides. The inability to break down gangliosides causes harmful quantities of this lipid to accumulate in nerve cells of the brain, eventually leading to premature death of affected cells. There is no known cure for the disease, and death usually occurs by age 4. Jack and Jill have a child who has Tay-Sachs. What do you know about the genotypes of Jack and Jill?
A. Its impossible to tell. Since both are adults, they do not have the disease. But, they could either be TT or Tt
B. Both are heterozygous
C. Both are tt
D. One is TT and the other is tt
E. Both are TT
Answer: B
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Which statement factors into artificial but not natural selection?
A. Most organisms are capable of producing more offspring than typically survive. B. Phenotypic variation of a species has variable appeal to humans interested in that species. C. Phenotypic variation exists within populations. D. Phenotypic variation can influence reproductive success. E. Phenotypic variation within a species is due in part to inherited characteristics.
A newborn is identified as having cystic fibrosis. While both parents are healthy, a genetic screening of both parents will most likely reveal:
A. the father is a carrier of the mutant CF allele. B. the mother is a carrier of the mutant CF allele. C. both mother and father are carriers of a mutant CF allele. D. neither mother nor father are carriers; spontaneous mutation caused the baby's disease.
Destructive outbreaks of pests are ____ in cultivated fields, which are low-diversity communities, than in natural
communities with greater species richness. a. less common b. more common c. equally common d. most easily prevented e. rarely occur
The dynamic constancy of the internal environment of animals, in which conditions such as temperature, pH, and nutrient concentrations are kept within narrow limits, is termed
A. negative feedback loop. B. the set point. C. osmoregulation. D. homeostasis