Question

Tallness of a pea plant is a dominant trait, dwarfness is the alternate recessive trait. A pure tall pea plant is crossed with a dwarf one. Work out the cross to show what fraction of the tall plants in the F2-generation is heterozygous. State any one law of Mendel which can be derived from this cross. a) 100% of tall plants are heterozygous, Law of Segregation b) 75% of tall plants are heterozygous, Law of Independent Assortment c) 50% of tall plants are heterozygous, Law of Dominance d) 25% of tall plants are heterozygous, Law of Segregation

Answer 1

In Mendelian genetics, when a pure tall pea plant is crossed with a dwarf plant, the offspring in the F2 generation will contain 50% heterozygous (Tt) tall plants. This supports Mendel's Law of Segregation, which predicts the separation and recombination of alleles during sexual reproduction.

Step-by-step explanation:

The dominant trait in the pea plant is tallness (T), while the recessive trait is dwarfness (t). When you cross a pure tall pea plant (TT) with a dwarf plant (tt), all offspring in the F1 generation will be tall, but they will be heterozygous (Tt), meaning they have one allele for tallness and one for dwarfness.

Moving on to the F2 generation, by crossing two heterozygous tall plants (Tt x Tt), you will generate 1 TT plant (homozygous tall), 2 Tt plants (heterozygous tall), and 1 tt plant (dwarf). It is clear that, out of the 3 tall plants (TT and Tt combined), 2 are heterozygous (Tt).

Hence, the answer is a) 50% of tall plants are heterozygous because out of the tall plants produced, half of them are heterozygous. The relevant Mendelian law is the Law of Segregation, which states that the two alleles for each trait segregate (separate) during gamete formation, and then unite at random during fertilization.

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