Neurofibromatosis type 1 (NF1) is an inherited is an inheritent dominant disorder. The phenotype usually involves the production of many skin neurofibromas. Answer the following questions about the disorder: a) Are the NF1 neurofibromatosis-causing mutations that are inherited by affected children from affected parents likely to be loss-of-function or gain-of-function mutations? b) Neurofibromin, the protein product of NF1, is associated with the Ras protein. Ras is involved in the transduction of extracellular signals from growth factors. The active form of Ras is complexed with GTP; the inactive form is complexed with GDP. Would the wild-type neurofibromin protein favor the formation of Ras-GTP or Ras-GDP? c) Which of the following events in a normal cell from an individual inheriting a neurofibromatosis-causing allele could cause the descendents of that cell to turn into a neurofibroma? i. A second point mutation in the allele of the NF1 inherited from the affected parent ii. A point mutation in the allele of the NF1 inherited from the normal parent iii. A large deletion that removes the NF1 gene from the chromosome inherited from the affected parent iv. A large deletion that removes the NF1 gene from the chromosome inherited from the normal parent v. Mitotic chromosomal nondisjunction or chromosome loss vi. Mitotic recombination in the region between the NF1 gene and and the centromere of the chromosome carrying NF1 vii. Mitotic recombination in the region between the NF1 gene and and the telomere of the chromosome carrying NF1
Neurofibromatosis type 1 (NF1) is an inherited is an inheritent dominant disorder. The
a) Are the NF1 neurofibromatosis-causing mutations that are inherited by affected children from affected parents likely to be loss-of-function or gain-of-function mutations?
b) Neurofibromin, the protein product of NF1, is associated with the Ras protein. Ras is involved in the transduction of extracellular signals from growth factors. The active form of Ras is complexed with GTP; the inactive form is complexed with GDP. Would the wild-type neurofibromin protein favor the formation of Ras-GTP or Ras-GDP?
c) Which of the following events in a normal cell from an individual inheriting a neurofibromatosis-causing allele could cause the descendents of that cell to turn into a neurofibroma? i. A second point mutation in the allele of the NF1 inherited from the affected parent ii. A point mutation in the allele of the NF1 inherited from the normal parent iii. A large deletion that removes the NF1 gene from the chromosome inherited from the affected parent iv. A large deletion that removes the NF1 gene from the chromosome inherited from the normal parent v. Mitotic chromosomal nondisjunction or chromosome loss vi. Mitotic recombination in the region between the NF1 gene and and the centromere of the chromosome carrying NF1 vii. Mitotic recombination in the region between the NF1 gene and and the telomere of the chromosome carrying NF1
d) The rarer form of neurofibromatosis is called segmental neurofibromatosis. In this form of the disease, neither parent of the patient has any clinical sign of the disease, and the tumors in the patient are restricted to one part of the body. Suggest an explanation for the genesis of segmental neurofibromatosis that clarifies why it is restricted to one part of the body.
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