In pea plants the colour of the peas is genetically controlled. Each pea represents a separate fertilisation. Smooth texture (S) is dominant to wrinkly (s) and green (G) colour is dominant to yellow (g). Following a breeding experiment with pea plants, the following ratio of pea phenotypes was found. Smooth and green : Smooth and yellow : wrinkly and green : wrinkly and yellow = 86 : 28 : 32 : 9. What is the most likely genotype of the parental plants?
a. SsGG and ssgg
b. SsGg and SsGg
c. SSGg and SsGg
d. SsGg and Ssgg
answer is b
To determine the most likely genotype of the parental plants, we need to consider the phenotypic ratios and understand the principles of inheritance.
The given phenotypic ratio of Smooth and green : Smooth and yellow : wrinkly and green : wrinkly and yellow is 86 : 28 : 32 : 9.
From this ratio, we can deduce the genotypes of the parental plants by working backwards.
Let's start by considering the dominant traits first. If smooth (S) is dominant over wrinkly (s) and green (G) is dominant over yellow (g), then the parental plants must have at least one dominant allele for each trait to produce the observed phenotypes.
Looking at the phenotypic ratio, there are 86 smooth and green peas, which means both traits are present.
Now, let's consider the genotypes of the parental plants based on the remaining ratios.
Smooth and green : Smooth and yellow : wrinkly and green : wrinkly and yellow = 86 : 28 : 32 : 9
Since there are 86 smooth and green peas, the parental plants must have at least one dominant allele for smooth texture (S) and green color (G).
To determine the most likely genotype, we need to find a combination that satisfies the observed ratio.
Considering option a) SsGG and ssgg, this genotype would produce 9 wrinkly and yellow peas. However, the observed ratio is 32 wrinkly and green peas. Therefore, option a) is not the most likely genotype.
Considering option b) SsGg and SsGg, this genotype would produce an equal number of smooth and yellow peas. However, the observed ratio is 28 smooth and yellow peas. Therefore, option b) is not the most likely genotype.
Considering option c) SSGg and SsGg, this genotype would produce 32 wrinkly and green peas, which matches the observed ratio. Therefore, option c) is a possible genotype.
Considering option d) SsGg and Ssgg, this genotype would produce 9 wrinkly and yellow peas, which also matches the observed ratio. Therefore, option d) is a possible genotype.
Based on the given information, both options c) and d) are possible genotypes for the parental plants.