Answer:
In a pedigree where the trait is present, the features exhibited will depend on the mode of inheritance.
Here are the features typically seen in pedigrees for each mode of inheritance:
1. Autosomal recessive inheritance:
- Affected individuals can have unaffected parents.
- The trait can skip generations.
- When both parents are carriers, there is a 25% chance for each child to be affected.
- Male and female individuals are equally affected.
- Example: Cystic fibrosis is an example of an autosomal recessive disorder.
2. Autosomal dominant inheritance:
- Affected individuals usually have at least one affected parent.
- The trait does not skip generations.
- When one parent is affected, there is a 50% chance for each child to be affected.
- Both males and females can be affected equally.
- Example: Huntington's disease is an example of an autosomal dominant disorder.
3. X-linked recessive inheritance:
- The trait is more commonly seen in males.
- Affected males usually have unaffected parents, as the trait is passed from carrier mothers.
- Sons of affected males do not inherit the trait, but all daughters are carriers.
- Example: Hemophilia is an example of an X-linked recessive disorder.
4. X-linked dominant inheritance:
- The trait can be seen in both males and females, but it is more commonly seen in females.
- Affected males pass the trait to all of their daughters and none of their sons.
- Affected females have a 50% chance to pass the trait to each of their children, regardless of gender.
- Example: Rett syndrome is an example of an X-linked dominant disorder.
5. Y-linked inheritance:
- The trait is only seen in males, as the Y chromosome is passed from father to son.
- Affected males pass the trait to all of their sons.
- There is no female-to-male transmission of the trait.
- Example: Y-linked infertility is an example of a Y-linked disorder.
These features help geneticists analyze pedigrees and determine the mode of inheritance for a specific trait or disorder.