How to solve questions related to Pedigree analysis?

Questions related to Pedigree analysis can be solved by following the steps given below:

Autosomal dominant

- when father transfers disease to his son -- it is always an autosomal trait.
- affected parents can have unaffected children.

- Pedigrees of autosomal dominant disorders show affected males and females in each generation and also show affected men and women transmitting the condition to equal proportions of their sons and daughters.

Autosomal recessive:

- there is skipping of generation
- unaffected parents can give affected children

X-linked dominant:

- the disorder never transfers from father to son
- it follows DDD rule (D= dominant, D= diseased dad, D= diseased daughters). It means, if father is affected, all daughters will be affected.

X-linked recessive:

- males are more affected than females
- disease tends to transfer from mother to son and father to daughter
- disease never transfers from father to son

If both parents are shown healthy -- it is often a recessive trait

When one or both the parents are shown as diseased -- it is often a dominant trait