Question

Write any two uses of pedigree study in human genetics.

Answer 1

Hint: Pedigree study is a hierarchical model to represent the flow of a particular trait down a family tree. It is made up of several symbols and lines representing genetic relationships.

Complete answer:
The two uses of pedigree study in human genetics are:
- It is a visual tool for documenting the biological relationship in families and determining the mode of inheritance of genetic diseases.
- These are often constructed by medical geneticists and practitioners to identify the persons who are the carriers of a particular disease and those that are affected. It also helps them to predict the affected individuals of progeny.
Some expected patterns of inheritance that can be observed in the pedigree are:
- Autosomal recessive inheritance: Such type of traits often skips generations with an equal number of males and females affected. All the children will be affected when both the parents are diseased.

- Autosomal dominant inheritance: In such inheritance, the traits do not skip generations. The distribution of the trait among both the sexes are almost equal. Also, when an affected person mates with an unaffected individual, half of its offspring will be affected too.
- Sex-linked recessive inheritance: The affected individuals are mostly male with no skipping in generations by the trait concerned. The affected males come only from an affected mother while an affected female can come from both an affected mother or father. Also, an affected father results in all of his daughters being affected but neither of his sons.

Note: Some symbols used in the pedigree are:
- Squares represent males while circles represent females. A horizontal line between these two symbols stands for their marriage.
- Vertical lines extending downwards represent their children. Thus, the newer generation can be found at the bottom of a pedigree while the older generations are found at the top of a generation.
- A fully shaded symbol denotes an affected individual while an unshaded symbol means a healthy individual. A partly shaded symbol denotes the carrier of a trait.