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.

Draw a pedigree of this family, including the woman, the man, their siblings, parents, and grandparents.

Verified step by step guidance

1. Draw the pedigree chart starting with the oldest generation at the top, which includes the grandparents of both the woman and the man.
2. For the woman's side, indicate that her paternal grandmother is heterozygous (Gg) and her paternal grandfather is homozygous dominant (GG).
3. For the woman's parents, show that her father is heterozygous (Gg) and her mother is homozygous dominant (GG).
4. For the woman and her sister, indicate that the woman is homozygous dominant (GG) and her sister is heterozygous (Gg).
5. For the man's side, indicate that he is heterozygous (Gg) and his brother has Gaucher disease (gg), and note that his parents and grandparents are not tested but do not have the disease.

Key Concepts

Gaucher Disease and Its Genetics

Gaucher disease is a genetic disorder caused by mutations in the GBA gene, leading to a deficiency in the enzyme glucocerebrosidase. It is inherited in an autosomal recessive manner, meaning that an individual must inherit two copies of the mutant allele (g) to express the disease. Carriers, who possess one dominant allele (G) and one mutant allele (g), do not show symptoms but can pass the mutant allele to their offspring.

Pedigree Analysis

A pedigree is a diagram that represents the genetic relationships and inheritance patterns within a family. It uses standardized symbols to denote individuals, their genders, and their health status regarding specific genetic conditions. Analyzing a pedigree helps in understanding how traits are passed through generations, identifying carriers, and predicting the likelihood of offspring inheriting certain genetic conditions.

Genotype and Phenotype

Genotype refers to the genetic makeup of an individual, specifically the alleles they carry for a particular gene, while phenotype is the observable expression of that genotype, influenced by both genetics and environmental factors. In the context of Gaucher disease, understanding the genotypes of the individuals in the pedigree is crucial for predicting the phenotypes of their offspring and assessing the risk of disease manifestation.