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Principles of Inheritance and Variation

Long Answer Type

41. A black-colour cock when bred with a white coloured hen produced steel blue coloured offspring and when inbred, black, white and steel-blue coloured progeny were obtained:
(a) This result is genetically explained as.
(b) What will be the expected ratio and proportions of black, steel-blue and white progeny?

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Short Answer Type

42.

Explain the following terms with example
(a) Co-dominance
(b) Incomplete dominance

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43. Differentiate incomplete dominance and codominance.

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Long Answer Type

44. In man four types of blood groups A, B, AB and O are controlled by three alleles of a gene. What is the mechanism of inheritance of the blood groups ?

ABO blood types in human is a classic example of multiple allelism and co-dominance where more than two allele forms are present for a trait and both A and B allele are dominant over i allele. Three different alleles I^A, I^B and i or I^O determine the phenotypes of the four blood groups.

Both I^A and I^B are dominant and express themselves over I^Oor i. I^Aand I^Bshow co-dominance and produce different forms of sugar wheras I^Oor i does not produce any sugar. The Thus the phenotypes produced are -:

I^AI^A and I^AI^O Produces the phenotype of A blood group.
I^BI^B and I^BI^Oproduces blood group B.
I^AI^Bproduces Blood group AB .
I^OI^O produces Blood group O.

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Short Answer Type

45. What will be the blood groups of the children of following matings ?

(a) IA IB x IBIB
(b) IAI° x IAIB
(c) IA IB x IAIB
(d) I° I° x IAIB.

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Long Answer Type

46.

Child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.

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