Dominant and Recessive Traits


 
 
Concept Explanation
 

Dominant and Recessive Traits

Notations used in Mendel’s experiments:

The dominant trait is usually represented by a capital letter. For example, tallness is represented by ‘T’ and dwarfness is represented by the corresponding small letter ‘t’. If tallness is due to a pair of dominant alleles, it is written as TT. If tallness is due to only one dominant allele, it is written as Tt. If both the alleles are recessive, making the organism dwarf, then it is written as tt. A homozygous condition is one in which both the alleles are of the same nature, e.g., TT or tt. A alleles are of different nature, e.g., Tt. When two heterozygous condition is one in which the characters are taken into account, the notation for the homozygous dominant could be AABB, and for the homozygous recessive it could be aabb. He performed following two experiments:

1. Inheritance of Traits for one Contrasting Character:

Mendel took pea plants with different characteristics such as height (tall and short plants).

  • The progeny produced from them (F1 -generation plants) were all tall. Mendel then allowed F1 progeny plants to undergo self-pollination.
  • In the F2-generation, he found that all plants were no three quarter were tall and one quarter of them were short. This observation indicated that both the traits of shortness and tallness were inherited in F1 -generation, but only the tallness trait was expressed in F1 -generation. This is known as the law of dominance
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    Sample Questions
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    Question : 1

    Mendel took _______________ to perform the experiment to understand inheritance of traits.

    Right Option : A
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    Question : 2

    Eye color in the fruit fly is said to be sex-linked. This simple means that the gene for eye colour is ______________________

    Right Option : D
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    Question : 3

    Which of the following are correct ?

    (a) In Mendel’s notation the dominant trait is represented by a capital letter.

    (b) Mendel took pea plants with different characteristics such as height (tall and short plants) for studying contrasting characters.

    Right Option : C
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