Q. What is the difference between phenotype and genotype. Explain with example of a cross.
Asked by Kushagra Pandya | 17th Mar, 2013, 06:20: PM
Phenotypic ratio is the ratio of the offspring's phenotype. In other words it is the ratio that shows the varied outcomes that results from a genetic cross and is based on physical appearance alone.
Genotypic ratio is the proportion of genotypes or alleles in a population of offspring produced by a particular cross.
1:2:1 and 3:1 are the genotypic and phenotypic ratios typically found in a monohybrid cross, when a homozygous recessive parent is crossed with a homozygous dominant parent.
Lets look at an example for this. On crossing a homozygous tall pea plant (TT) with a homozygous short pea plant (Tt), in F1 generation, all offspring were tall (Tt).
On self fertilising the F1 plants, the offsprings were found to be tall as well as short in the ratio of 3 tall:1 short. This is the phenotypic ratio. Their genotypes were as follows - 1 short (tt) : 2 tall (Tt) : 1 tall (TT). (Remember that Tt and TT are both expressed as tall)
Answered by | 18th Mar, 2013, 09:09: PM
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