Familial adenomatous polyposis (FAP) is an inherited disorder characterized by c
ID: 133396 • Letter: F
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Familial adenomatous polyposis (FAP) is an inherited disorder characterized by cancer of the large intestine. People with the classic type of FAP may begin to develop multiple noncancerous (benign) growths in the colon as early as their teenage years. Unless the colon is removed, these growths will become malignant (cancerous). The average age at which an individual develops colon cancer in classic FAP is 39 years. The disease is caused by mutations in MUTYH, a gene encoding a DNA repair enzyme. Mutant alleles of MUTYH exhibit autosomal recessive inheritance. The disease is relatively common, affecting 1 in 7,000 adults. One of the most common mutant alleles of the MUTYH gene contains an insertion of 142 nucleotides in the coding sequence.Three sisters in their teens have an older brother who was diagnosed with FAP, but neither parent, now in their 60s, has the disease. A genetic test revealed that the brother developed the disease because he is homozygous for the common insertion allele of MUTYH.
What can be said about the genotypes of the parents? -Select an Option- Select an Option Both parents are heterozygous for the nucleotide insertion allele. One parent is homozygous for the nucleotide insertion allele. One parent is heterozygous for the nucleotide insertion allele. Both parents are homozygous for the nucleotide insertion allele. --Explanation / Answer
both parents are homozygous for the nucleotide insertion allele, because it is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. Most often, the parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but do not show signs and symptoms of the condition.
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