A couple and some of their relatives are screened for Gaucher disease in a community-based screening program. The woman is homozygous for the dominant allele, represented by G. The woman's father, sister, and paternal grandmother are heterozygous carriers of the mutant allele, represented by g. Her paternal grandfather, her mother, and both of her mother's parents are homozygous for the dominant allele. The man is heterozygous and he has a brother with Gaucher disease. The man's parents and grandparents have not been tested, but it is known that none of them has Gaucher disease.
On the pedigree, write the genotypes (GG, Gg, or gg) for each person who has been tested or for whom you can deduce a genotype. If a genotype cannot be determined completely, list the alleles you know or deduce must be present.
Suppose crossover occurs between the homologous chromosomes in the previous problem. At what stage of M phase do alleles D and d segregate?
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Key Concepts
Crossover
06:14
M Phase
08:34Segregation of Alleles
03:03A couple and some of their relatives are screened for Gaucher disease in a community-based screening program. The woman is homozygous for the dominant allele, represented by G. The woman's father, sister, and paternal grandmother are heterozygous carriers of the mutant allele, represented by g. Her paternal grandfather, her mother, and both of her mother's parents are homozygous for the dominant allele. The man is heterozygous and he has a brother with Gaucher disease. The man's parents and grandparents have not been tested, but it is known that none of them has Gaucher disease.
Explain why you are able to assign genotypes to the man's parents despite their not being tested.
Explain how the behavior of homologous chromosomes in meiosis parallels Mendel's law of segregation for autosomal alleles D and d. During which stage of M phase do these two alleles segregate from one another?
If a man and a woman are each heterozygous carriers of a mutation causing a disease on the RUSP list, what do you think are the three or four most important factors they should consider in their decision making about having children?
Suppose a man and a woman are each heterozygous carriers of a mutation causing a fatal hereditary disease not on the RUSP list. Prenatal genetic testing can identify the genotype of a fetus with regard to this disease and can identify fetuses with the disease. What do you think are the three or four most important factors this couple should consider in their decision making about having children?
How many Barr bodies are found in a normal human female nucleus? In a normal male nucleus?