17. You are a genetic counselor, and it is your job to predict the liklihood of certain couples having babies with genetic disorders. A woman named Nichole comes seeking your help because she has a family history of Duchenne Muscular Dystrophy, an X-linked, recessive genetic disorder. Nichole wants to have kids with her husband who has no family history of the disorder, but she is concerned that her child may be born with the disorder. Her father had muscular dystrophy. Nichole does not have muscular dystrophy, and her brother and sister also do not show the trait. Her brother has a healthy daughter and son. However, her sister has one son who suffers from muscular dystrophy, and one son who is healthy. Draw a complete pedigree of Nichole's family, and determin if it is possible for Nichole to pass the trait on to her offspring. If she can pass the trait, what is the probability that she will have a child with muscular dystrophy. What is the liklihood that she will have a child who is a carrier (a carrier can pass a trait to her offspring, but she does not exhibit the trait).

17. You are a genetic counselor, and it is your job to predict the liklihood of certain couples having babies with genetic disorders. A woman named Nichole comes seeking your help because she has a family history of Duchenne Muscular Dystrophy, an X-linked, recessive genetic disorder. Nichole wants to have kids with her husband who has no family history of the disorder, but she is concerned that her child may be born with the disorder. Her father had muscular dystrophy. Nichole does not have muscular dystrophy, and her brother and sister also do not show the trait. Her brother has a healthy daughter and son. However, her sister has one son who suffers from muscular dystrophy, and one son who is healthy. Draw a complete pedigree of Nichole's family, and determin if it is possible for Nichole to pass the trait on to her offspring. If she can pass the trait, what is the probability that she will have a child with muscular dystrophy. What is the liklihood that she will have a child who is a carrier (a carrier can pass a trait to her offspring, but she does not exhibit the trait).

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter11: Genome Alterations: Mutation And Epigenetics

Section: Chapter Questions

Problem 7QP

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A couple was referred for genetic counseling because they wanted to know the chances of having a child with dwarfism. Both the man and the woman had achondroplasia (MIM 100800), the most common form of short-limbed dwarfism. The couple knew that this condition is inherited as an autosomal dominant trait, but they were unsure what kind of physical manifestations a child would have if it inherited both mutant alleles. They were each heterozygous for the FGFR3 (MIM 134934) allele that causes achondroplasia. Normally, the protein encoded by this gene interacts with growth factors outside the cell and receives signals that control growth and development. In achrodroplasia, a mutation alters the activity of the receptor, resulting in a characteristic form of dwarfism. Because both the normal and mutant forms of the FGFR3 protein act before birth, no treatment for achrondroplasia is available. The parents each carry one normal allele and one mutant allele of FGRF3, and they wanted information on their chances of having a homozygous child. The counsellor briefly reviewed the phenotypic features of individuals with achondroplasia. These include facial features (large head with prominent forehead; small, flat nasal bridge; and prominent jaw), very short stature, and shortening of the arms and legs. Physical examination and skeletal X-ray films are used to diagnose this condition. Final adult height is approximately 4 feet. Because achondroplasia is an autosomal dominant condition, a heterozygote has a 1-in-2, or 50%, chance of passing this trait to his or her offspring. However, about 75% of those with achondroplasia have parents of average size who do not carry the mutant allele. In these cases, achondroplasia is due to a new mutation. In the couple being counseled, each individual is heterozygous, and they are at risk for having a homozygous child with two copies of the mutated gene. Infants with homozygous achondroplasia are either stillborn or die shortly after birth. The counselor recommended prenatal diagnosis via ultrasounds at various stages of development. In addition, a DNA test is available to detect the homozygous condition prenatally. Should the parents be concerned about the heterozygous condition as well as the homozygous mutant condition?
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