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Please find below the answer:
In Mendel Experiment when a Pure Tall plant is crossed with pure Dwarf, aa the offsprings obtained are Tall.
This can be explained as
- Since, Tall is the dominant trait for height , A Pure Tall plant contains both the alleles of dominant trait. i.e. TT (Homozygous)
- Dwarf is a recessive trait for height. A pure Dwarf plant contains both the alleles of recessive trait i.e. tt (Homozygous)
- When a Pure Tall is made to reproduce with a Pure Dwarf Plant then all offsprings of first generation are Tall as
Gametes T t
First Generation Tt (Heterozygous)
- All pea plant of first-generation Contain the same alleles and hence all show the same phenotype i.e. Tall
- They appear Tall in their phenotype because according to law of Dominance given by Mendel, if a gene contains 2 different alleles ( Heterozygous ) then only one allele ie. Dominant allele shows its effect and masks the effect of recessive allele.
- Therefore in Plants with Tt genotype, only the T allele shows its effect and plants thus, appear TALL.
F2 generation is obtained by selfing the individuals of the F1 generation. The individuals of the F2 generation have homozygous as well as heterozygous genotype. The genotypic ratio is 1:2:1 and the phenotypic ratio is 3:1.
F2 generation:
| Gametes | T | t |
| T | TT | Tt |
| t | Tt | tt |
The above cross establishes the law of dominance and the law of segregation.
Law of Dominance
1. According to this law, characters are controlled by discrete units called factors, which occur in pairs with one member of the pair dominating over the other in a dissimilar pair.
2. This law explains the expression of only one of the parental character in F1 generation and expression of both in F2 generation.
Law of Segregation
1. This law states that the two alleles of a pair segregate or separate during gamete formation such that a gamete receives only one of the two factors.
2. In homozygous parents, all gametes produced are similar; while in heterozygous parents, two kinds of gametes are produced in equal proportions.
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