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Question
By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is dominant over yellow pod colour (g)) in Garden pea with unknown genotype.
Solution
A test cross is formed by crossing a parent with an unknown genotype with another parent who has a homozygous recessive genotype. A test cross determines or reveals the original person's genotype. A test cross can help determine whether a dominant phenotype is homozygous or heterozygous for a specific trait.
Given:
Dominant allele: G
Dominant trait: Green pod colour
Recessive allele: g
Recessive trait: yellow pod colour
Case 1:
Genotypic ratio: 100% heterozygous dominant i.e., 1 : 0 ratio.
Phenotypic ratio: all green
Inference: Unknown is homozygous dominant
Case 2:
Genotypic ratio: 50% heterozygous dominant and 50% homozygous recessive i.e., 1 : 1 ratio.
Phenotypic ratio: 50% Green: 50% Yellow
Inference: Unknown is heterozygous dominant.
RELATED QUESTIONS
The production of gametes by the parents, the formation of zygotes, and the F1 and F2 plants, can be understood from a diagram called ______
A true breeding pea plant, homozygous dominant for inflated green pods is crossed with another pea plant with constricted yellow pods (ffgg). With the help of Punnett square show the above cross and mention the results obtained phenotypically and genotypically in F1 generation.
