Marfan syndrome is an autosomal dominant disorder in humans. It results from mutation of a gene on chromosome 15 that produces the connective tissue protein fibrillin. In its wild-type form, fibrillin gives connective tissues, such as cartilage, elasticity. When mutated, however, fibrillin is rigid and produces a range of phenotypic complications, including excessive growth of the long bones of the leg and arm, sunken chest, dislocation of the lens of the eye, and susceptibility to aortic aneurysm, which can lead to sudden death in some cases. Different sets of symptoms are seen among various family members, as shown in the pedigree below. Each quadrant of the circles and squares represents a different symptom, as the key indicates.
All cases of Marfan syndrome are caused by mutation of the fibrillin gene, and all family members with Marfan syndrome carry the same mutant allele. What do the differences shown in the phenotypes of family members say about the expression of the mutant allele?

Question

Marfan syndrome is an autosomal dominant disorder in humans. It results from mutation of a gene on chromosome 15 that produces the connective tissue protein fibrillin. In its wild-type form, fibrillin gives connective tissues, such as cartilage, elasticity. When mutated, however, fibrillin is rigid and produces a range of phenotypic complications, including excessive growth of the long bones of the leg and arm, sunken chest, dislocation of the lens of the eye, and susceptibility to aortic aneurysm, which can lead to sudden death in some cases. Different sets of symptoms are seen among various family members, as shown in the pedigree below. Each quadrant of the circles and squares represents a different symptom, as the key indicates.

All cases of Marfan syndrome are caused by mutation of the fibrillin gene, and all family members with Marfan syndrome carry the same mutant allele. What do the differences shown in the phenotypes of family members say about the expression of the mutant allele?

Pedigree chart illustrating Marfan syndrome symptoms: long bones, lens dislocation, sunken chest, and aortic aneurysm.

All cases of Marfan syndrome are caused by mutation of the fibrillin gene, and all family members with Marfan syndrome carry the same mutant allele. What do the differences shown in the phenotypes of family members say about the expression of the mutant allele?

Accepted Answer

Hello, everyone and welcome to today's video. So N F one is a disease inherited condition that follows an autosomal dominant pattern and it is caused by mutation in the N F one gene. The N F one gene plays a vital role in the production of narrow fibromy, a protein that helps regulate cell growth and division. The disorder can affect different areas of the body such as the skin bones and the nervous system. The symptoms can vary widely among individuals with the conditions. Some may have a few cafe iate spots while others may have numerous benign tumors called neurofibroma. Additionally, some individuals carrying the N F one mutation may not exhibit symptoms at all while others may experience severe symptoms. So which of the following terms best describes disease. A, we have constant expressivity and incomplete penetrance. B, we have constant expressivity and complete penetrance. C we have variable expressivity and incomplete penetrance. And D we have variable expressivity and incomplete penetrance. So in order to solve this problem, we need to break down some of the terms that were given in it. First of all, because the disease or the symptoms of the disease can vary such as some people having benign tumors called neurofibroma while others having only a few spots because the symptoms can vary. We call this variable expressivity. Now, additionally, some individuals carrying the N F O mutation are not exhibiting symptoms at all while others are exhibiting very severe symptoms. And when this occur, when this is occurring, we we call this incomplete penetrance. So we're going to highlight these two terms, incomplete penetrance and variable expressivity. Making the correct answer choice for this question answer, choice, C variable expressivity and incomplete penetrance. I really hope this video helped you and I hope to see you on the next one.

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Key Concepts

Autosomal Dominance

Phenotypic Variation

Fibrillin and Connective Tissue