Question

Which of the following is a deviation from Mendelian principle ?

• A. Inheritance of AB blood groups in man
• B. Inheritance of flower colour in Mirabilis jalapa
• C. Inheritance of cotyledon colour in Pisum sativum
• D. Inheritance of AB blood group in man and flower colour in Mirabilis jalapa

Answer 1

The correct option is D Inheritance of AB blood group in man and flower colour in Mirabilis jalapa

Co-dominance	A	B
A	AA	AB
B	AB	BB

Incomplete dominance	R	r
R	RR	Rr
r	Rr	rr

Inheritance of AB blood group in human follows co-dominance while inheritance of flower colour in Mirabilis jalapa follows incomplete dominance.

Co-dominance is a form of dominance where alleles of a gene pair in a heterozygote are fully expressed. In AB blood group, both A and B alleles are fully expressed. Therefore, an individual has neither A nor B blood group but AB blood group.

Incomplete dominance is a form of inheritance in which one allele for a specific trait is not completely expressed over its paired allele. In Mirabilis jalapa, plants with Rr genotype are not red (dominant allele) but pink (a third phenotype produced as a result of a combination of other two phenotypes).

So, the correct option is 'Inheritance of AB blood group in man and flower colour in Mirabilis jalapa'.