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Sickle-cell anaemia as well as thalassem...

Sickle-cell anaemia as well as thalassemia are autosomal recessive diseases.
Why are these diseases more common than expected in certain areas?

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Persons heterozygous for sickle-cell trait and thalassemia are more numerous in some African groups living in areas infested with malaria, because malarial parasite is unable to survive in sickle-shaped RBCs or has chances of survival in thalassemic persons. So these heterozygotes are resistant to malaria and are favoured by natural selection.
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ICSE-PRINCIPLES OF INHERITANCE AND VARIATION-MULTIPLE CHOICE QUESTION
  1. Sickle-cell anaemia as well as thalassemia are autosomal recessive dis...

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  2. The genetic ratio of 9:3:3:1 is due to:

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  3. Choose the chromosome, in a human, that possesses least number of gene...

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  4. G. J. Mendel was a:

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  5. Select the incorrect match.

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  6. In a dihybrid cross, if you get 9:3:3:1 ratio it denotes that:

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  7. A monohybrid cross produced tall and dwarf pea plants in ratio of 3:1....

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  8. Common test to find genotype of hybrid is by:

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  9. Which one is a test cross?

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  10. Mating of an organism to a double recessive in order to determine whet...

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  11. A cross between two tall plants resulted in offspring having few dwarf...

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  12. The term genetics was proposed by:

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  13. The F2 genotypic ratio of monohybrid cross is:

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  14. A dihybrid for qualitative trait is crossed with homozygous recessive ...

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  15. In order to find out the different types of gametes produced by a pea ...

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  16. The autosomal disorder/disease in humans is:

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  17. Distance between the genes and percentage of recombination shows:

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  18. In Mirabilis jalapa, the number of F2 red flowered plants in a cross ...

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  19. In pea plants, yellow seeds are dominant to green. If a heterozygous y...

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  20. Which of the following is best suited for codominance?

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  21. Incomplete dominance is shown by:

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