Asked by Nishu Singh on May 12, 2024
Verified
Which of the following crosses will yield four phenotypes in a ratio of 9:3:3:1?
A) RRYY × RRYY
B) RRYY × rryy
C) RrYy × RrYy
D) RrYy × rryy
E) rryy × rryy
Phenotypes
The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
Genotypes
The genetic constitution of an organism, determining its specific traits.
- Engage with Mendelian genetics principles to forecast outcomes in monohybrid and dihybrid crossing experiments.
- Estimate the distribution of phenotypic and genotypic traits in offspring originating from different genetic cross scenarios.
Verified Answer
PP
priya parateMay 13, 2024
Final Answer :
C
Explanation :
The cross between RrYy and RrYy will yield four phenotypes in a 9:3:3:1 ratio due to the presence of two different genes that exhibit complete dominance and independent assortment. The capital "R" and "Y" alleles will result in a dominant phenotype, whereas the lowercase "r" and "y" alleles will result in a recessive phenotype. When two heterozygous individuals (RrYy) are crossed, the resulting offspring will have the following genotypes and phenotypes:
- 9/16 will be RY and display the dominant phenotype
- 3/16 will be RrYy and display the dominant phenotype
- 3/16 will be RY and display the recessive phenotype
- 1/16 will be rryy and display the recessive phenotype
Thus, the ratio of dominant to recessive phenotypes is 12:4 or 3:1, while the ratio of the two dominant phenotypes to each other is 9:3 or 3:1. None of the other crosses will yield a 9:3:3:1 phenotypic ratio.
- 9/16 will be RY and display the dominant phenotype
- 3/16 will be RrYy and display the dominant phenotype
- 3/16 will be RY and display the recessive phenotype
- 1/16 will be rryy and display the recessive phenotype
Thus, the ratio of dominant to recessive phenotypes is 12:4 or 3:1, while the ratio of the two dominant phenotypes to each other is 9:3 or 3:1. None of the other crosses will yield a 9:3:3:1 phenotypic ratio.
Learning Objectives
- Engage with Mendelian genetics principles to forecast outcomes in monohybrid and dihybrid crossing experiments.
- Estimate the distribution of phenotypic and genotypic traits in offspring originating from different genetic cross scenarios.