Question

Describe Mendel’s experiments from the P generation to the F2 generation. Use a Punnett square to illustrate his experiments, but make sure to describe them and not just draw the Punnett squares. Use these experiments to also explain the difference between genotype and phenotype and also explain how the results would change if there was incomplete dominance.

Answer 1

Answer-

Mendel's experiment with height of pea plant.

P1- TT. x. tt

F1-

	t	t
T	Tt	Tt
T	Tt	Tt

Mendel crossed a pure breed tall plant with a pure breed short plant and got all tall offsprings in the first generation all offsprings were tall ,so he called the visible trait as dominant and the invisible trait as recessive.

The he crossed the F1 offsprings or say selfed the F1 offsprings.

P2-. Tt x Tt

	T	t
T	TT	Tt
t	Tt	tt

The genotypic ratio is TT: Tt: tt so 1:2:1

Phenotypic ratio is tall : short ,so 3:1

In the second generation on selfing a heterozygous parent ,the F2 generation had 3 tall plants and 1 short offsprings. So the recessive trait reappeared in this generation in few plants .

Phenotype is the physical ecpression of a trait . Gor example a plant is tall then tall is the phenotype.

Genotype is the genetic composition ,the composition of alleles in a gene. Like TT,Tt,tt are all genotypes.

If there was incomplete dominance while crosaing the homozygous dominant and homozygous recessive parents in generation 1 ,all offsprings would be medium height. That is neither short nor tall.

On selfing the medium plants in generation 2 there would be 1 tall ,1 short and 2 medium plants.

In incomplete dominance in heterozygpus conditions the dominant trait is nor expresed ,instead a third intermediate trait will be seen . Both dominant and recessive traits merge.

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