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NEET2021ZoologyPrinciples of Inheritance and VariationActual

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

Options

  1. A50   %
  2. B75   %
  3. C25   %
  4. D100   %

Correct answer

C. 25   %

Step-by-step solution

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 :

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