Question

Study the given pedigree chart and answer the question that follows: Give the genotypes of parents shown in generation I and their third child shown in generation II and the first grandchild shown in generation III.

Answer 1

Hint: Pedigree is defined as the inheritance of certain traits for two or more generations presented in the form of a family tree. It is also known as genealogy or case history.

Complete answer:
Pedigree analysis is the study of specific traits that is inherited from one generation to the next.Galton started the pedigree analysis. It is represented with the help of different symbols and the line tells about the genetic relationships.
Square depicts male whereas circle depicts female. The new generation is found in the last of pedigree while the older generation is found in the top. A fully shaded means there is an affected individual whereas shaded means the individual is healthy and partly shaded means the individual is a carrier of traits. Different uses of Pedigree are: 1)Genetic counselors use pedigree analysis to advise the couple regarding the probability of genetic defects in their children. 2) It gives the idea that Mendelian principles are applicable to human genetics. 3) It tells whether the DNA is transmitted from one generation to another. 4) Presence or absence of heterozygous and homozygous states can be known. 5) It helps in knowing the genetic disorders in animals also.
In this chart all the generations are affected so obviously the dominant trait is there. Dominant trait means when the genotype is phenotypically expressed in the heterozygous as it has only one copy of that gene. At the same time both the sex male and female are equally affected in all the generation so the trait found here is autosomal trait. Autosomal trait means when the specific trait is inherited.Autosomal trait occurs due to the mutation in chromosome 1 through 22.
So if A is the dominant allele for a trait then a will be a recessive allele. Therefore the genome of generation 1 parents is aa and Aa and for the third child in the generation II is Aa and the genotype of first grandchild III is Aa.

Note: Pedigree analysis helps in knowing the genetically inherited diseases so that it cannot be transmitted from one generation to another. The recessive and dominant traits can be known easily by pedigree chart.