Question

Study the above pedigree of an autosomal recessive disorder and identify genotypes of $IA,IIA$ & $IIB$ from the given options

• A. $Aa,Aa,Aa$
• B. $AA,Aa,AA$
• C. $AA,Aa,Aa$
• D. $AA,AA,Aa$

Answer 1

The correct option is A $Aa,Aa,Aa$

In case of autosomal recessive inheritance, affected offsprings will have unaffected heterozygous parents (mostly). When the heterozygous parents mate and the recessive allele gets randomly segregated, ultimately expressing a homozygous recessive trait in the offspring, only then the disease will become evident. This is the basic rule of such kind of genetic inheritance. All the affected offsprings on tracing back in the pedigree will give a heterozygous parent, so IA, IIA, and IIB will have the genotype of Aa, Aa and Aa.

So the correct option is 'Aa, Aa, Aa'.