In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased?NEET 2021

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TestHub · Accepted Answer

Since both the parents are heterozygous for sickle-cell anaemia, i.e., shows sickle-cell trait, they are represented by the symbol ${Hb}^{A} {Hb}_{}^{S}$ . Each parent thus will produce two types of gametes; one having a composition ${Hb}^{A}$ and the other having a composition for sickle cell anaemia as ${Hb}^{S}$ . The progeny cross will be as follows:

Progeny:

	${Hb}^{A}$	${Hb}^{S}$
${Hb}^{A}$	${Hb}^{A} {Hb}^{A}$ (Normal)	${Hb}^{A} {Hb}^{S}$ (Sickle-cell trait)
${Hb}^{S}$	${Hb}^{A} {Hb}^{S}$ (Sickle-cell trait)	${Hb}^{S} {Hb}^{S}$ (Diseased)

Phenotypic ratio: Normal: Sickle-cell trait: Diseased: $1 : 2 : 1$
Thus, $25 %$ of the progeny will be affected.

Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

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