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If 75% of the offsprings show dominant character, the parents are-
A. Both recessive.
B. Both hybrids.
C. Both dominants.
D. One dominant one recessive.

seo-qna
Last updated date: 27th Feb 2024
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IVSAT 2024
Answer
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Hint: Offsprings inherit characters from their parents. In case of sexual reproduction, offspring inherit the characters from both the parents.

Complete Answer:
- An organism is called homozygous when both the allelic forms of a gene pair are the same. An organism could be homozygous dominant i.e. express dominant form (TT) or homozygous recessive (tt).
- An organism is called heterozygous when it expresses two alternate forms of a gene pair together (Tt).
- If both the parents crossed will be recessive all the offspring will be recessive. For example, when both the parents have dwarf height all the offspring formed from the cross will be dwarf.
- If both the parents are dominant, then the offsprings will also be dominant. For example, if both the parents have tall height all the offspring of the parents will be tall.
- If both the hybrid parents will be crossed, 50% offspring will be heterozygous dominant, 25% homozygous dominant and 25% recessive. All over phenotypically, 75% of the offspring will be dominant (Tt×Tt- 25% TT. 50% Tt and 25% tt i.e. 75% dominant and 25% recessive).

So, the correct option is B, i.e. both hybrids.

Note: In case of one dominant and one recessive parent, the dominant parent could be homozygous or heterozygous. If a homozygous dominant parent is crossed with a recessive parent all the offspring will be heterozygous dominant (TT×tt- all offspring will be Tt). If a heterozygous dominant parent is crossed with a recessive parent 50%of the offspring will be heterozygous dominant and 50% will be recessive (Tt×tt- 50%Tt and 50% tt).