A woman's father has ornithine transcarbamylase deficiency (OTD), an X-linked recessive disorder producing mental deterioration if not properly treated. The woman's mother is homozygous for the wild-type allele.

For the instance you identified in part (d), what proportion of daughters produced by the woman and the man are expected to have OTD? What proportion of sons of the woman and the man are expected to have OTD?

Key Concepts

X-Linked Inheritance

X-linked inheritance refers to the pattern of inheritance for genes located on the X chromosome. In X-linked recessive disorders, such as ornithine transcarbamylase deficiency (OTD), males (XY) are more likely to express the disorder because they have only one X chromosome. Females (XX) can be carriers if they have one affected X chromosome and one normal X chromosome, but they typically do not express the disorder unless both X chromosomes are affected.

Genotype and Phenotype

Genotype refers to the genetic constitution of an individual, while phenotype is the observable expression of that genotype. In the context of OTD, the genotype of the woman (carrier) and her partner will determine the phenotypic outcomes in their offspring. Understanding how these genotypes combine is crucial for predicting the likelihood of children inheriting the disorder.

Punnett Square

A Punnett square is a diagram used to predict the genetic outcomes of a cross between two individuals. It helps visualize the possible combinations of alleles from each parent, allowing for the calculation of probabilities for offspring genotypes and phenotypes. In this case, it can be used to determine the expected proportions of daughters and sons with OTD based on the parents' genotypes.