In a dihybrid cross, SsYy x SsYy, what fraction of the offspring will be homozygous for both traits?
1 Answer
In the given dihybrid cross, 25% (1/4th) fraction of the offsprings will be homozygous for both the traits.
Explanation:
The dihybrid cross in question is:
SsYy X SsYy
According to the law of independent assortment each of the two plants in dihybrid cross will produce the following 4 types of gametes:
SY, Sy, sY and sy
The genotypes of the offsprings by random fusion of the gametes produced by two plants can be calculated by checker board method.
There will be 16 possible combinations. Out of these 4 combinations will have genotype homozygous for both the traits , irrespective of dominant or recessive allele. These combinations are as follows:
SSYY, SSyy, ssYY and ssyy. or can be written as SYSY, SySy, sYsY and sysy
Thus 1/4th or 25% fraction of the population approximately will be homozygous for both the traits.
The fraction will be approximate as observed results are always closer to the calculated value as these are based on law of probability.
