Q20 of 30 Page 1

How are dominance, codominance and incomplete dominance patterns of inheritance different from each other?

In Dominance type of inheritance one of the alleles represents itself in F2 generation with a ratio of 4:1 and is expressed even in heterozygous condition. e.g. Tall(T), Axial (A), etc. In Codominance both alleles are expressed and in codominance F1 generation resembles both of the parents. E.g. blood group, etc.

In Incomplete Dominance the progeny resembles neither of the parent. E.g. as in dragon flower when a red flower is crossed with white flower the progeny obtained is of pink flowers and do not resemble either of the parents.


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Explain how a hereditary disease can be corrected. Give an example of first successful attempt made towards correction of such diseases.

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Draw a diagram of a male gametophyte of an angiosperm. Label any four parts. Why is sporopollenin considered the most resistant organic material?

 21

The base sequence in one of the strands of DNA is TAGCATGAT.

(i) Give the base sequence of its complementary strand.


(ii) How are these base pairs held together in a DNA molecule?


(iii) Explain the base complementarity rules. Name the scientist who framed this rule.


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(a) Sickle celled anaemia in humans is a result of point mutation. Explain.

(b) Write the genotypes of both the parents who have produced a sickle celled anaemic offspring.