Question

Above pedigree chart show

A. Autosomal dominant trait
B. Sex-linked recessive trait
C. Autosomal recessive trait
D. Sex-linked dominant trait

Answer 1

A pedigree is a systematic listing (either as words or symbols) of the ancestors of a given individual, or it may be the "family tree" for a number of individuals. In these charts, females are represented as circles and males as squares.

Complete Answer:
- In this pedigree chart Mating is shown as horizontal lines between two individuals. The offspring of a mating are connected by vertical line to the mating line. Different shades or colours added to the symbols can represent various phenotypes.
- In the above given pedigree chart, it can be seen that affected individuals are found in every generation which means it’s a dominant trait because recessive traits occur in alternate generations only. So it can be concluded that affected individuals are due to the dominant allele of a particular trait present in them.
- It also shows that the male and female are equally affected at every generation which means it is autosomal trait because sex-linked affects particular sex only.

The correct option is (A) i.e. autosomal dominant trait.

Note: In human beings pedigree analysis is used to know the transmission of specific traits because of following reasons:
- Mating cannot be controlled. To set up controlled mating experiments are not ethical or feasible.
- Generation time is long in human beings, so it takes a long time to track inheritance of traits over more than one generation.
- The total number of offspring per mating is limited, so phenotypic ratios are uncertain.