05-16-2011, 08:23 PM
Choose one of the following terms that best matches each clinical vignette. Each term may be used once, more than once, or not at all.
A. Incomplete penetrance
B. Allelic heterogeneity
C. Anticipation
D. Variable expressivity
E. Locus heterogeneity
1. A 24-year-old woman with myotonic dystrophy has significant muscle weakness and wasting. She has a one-year-old son with very poor muscle tone and severe weakness and significant developmental delay. Her affected 55-year-old father has cataracts but no muscle weakness.
A B C D E
2. A man and a woman, each of whom has autosomal recessive congenital deafness, have four biological children, each of whom has normal hearing.
A B C D E
3. A 40-year-old man with neurofibromatosis (NF1) has a plexiform neurofibroma of his leg that has caused significant disfigurement, and hundreds of cutaneous neurofibromas. His 43-year-old sister has cafe-au-lait spots and Lisch nodules of the iris, but no neurofibromas. His 19-year-old son has cafe-au-lait spots, a dozen cutaneous neurofibromas, and scoliosis (curvature of the spine).
A B C D E
4. Molecular analysis of the ornithine transcarbamylase (OTC) gene is carried out on two unrelated boys with X-linked OTC deficiency. One is found to have a large deletion in the 5' end of the gene; the other has a missense mutation in an exon toward the 3' end of the gene.
A B C D E
A. Incomplete penetrance
B. Allelic heterogeneity
C. Anticipation
D. Variable expressivity
E. Locus heterogeneity
1. A 24-year-old woman with myotonic dystrophy has significant muscle weakness and wasting. She has a one-year-old son with very poor muscle tone and severe weakness and significant developmental delay. Her affected 55-year-old father has cataracts but no muscle weakness.
A B C D E
2. A man and a woman, each of whom has autosomal recessive congenital deafness, have four biological children, each of whom has normal hearing.
A B C D E
3. A 40-year-old man with neurofibromatosis (NF1) has a plexiform neurofibroma of his leg that has caused significant disfigurement, and hundreds of cutaneous neurofibromas. His 43-year-old sister has cafe-au-lait spots and Lisch nodules of the iris, but no neurofibromas. His 19-year-old son has cafe-au-lait spots, a dozen cutaneous neurofibromas, and scoliosis (curvature of the spine).
A B C D E
4. Molecular analysis of the ornithine transcarbamylase (OTC) gene is carried out on two unrelated boys with X-linked OTC deficiency. One is found to have a large deletion in the 5' end of the gene; the other has a missense mutation in an exon toward the 3' end of the gene.
A B C D E
