Final answer:
In a pedigree, a woman infected with a disease is represented by a shaded circle. This standard symbol helps track inheritance patterns of genetic diseases. In X-linked recessive diseases, shaded circles indicate affected females, while half-shaded or dotted circles represent carriers.
Step-by-step explanation:
In a pedigree chart, a woman that is infected with a disease is typically represented by a shaded circle. The pedigree illustrates familial relationships and the transmission of genetic traits across generations. Women, in general, are symbolized by circles and men by squares. When tracing the inheritance of a genetic disorder, those affected by the disease are often indicated by the fully shaded symbol corresponding to their gender. For example, in the case of an X-linked recessive disease, female carriers may be depicted with a circle that is half-shaded or with a dot in the middle to indicate carrier status but not affected. However, females who have the disease will have a completely shaded circle. This helps geneticists and medical professionals track the inheritance of diseases such as sickle cell anemia or ALD and assess the genetic risks for offspring.
In the specific context of X-linked recessive illnesses, females can have a normal genotype, can be carriers of the disease without showing symptoms, or can be affected if they inherit the recessive gene from both parents. The symbols used in a pedigree are standardized to quickly convey the inheritance patterns and status of family members regarding specific genetic traits or diseases.