Possible response:

Genotypic and Phenotypic Ratios of Self-Pollinating Plant YyRr

When a plant YyRr is self-pollinated, the alleles for two pairs of traits (Yy and Rr) will segregate independently during meiosis and recombine randomly in the gametes. This will produce four possible gamete types with equal probability: YR, Yr, yR, and yr. When these gametes fuse randomly in fertilization, they will form offspring with different combinations of alleles and phenotypes.

The genotypic ratio refers to the proportion of different genotypes among the offspring, whereas the phenotypic ratio refers to the proportion of different physical or functional traits among the offspring. In this case, we can use a Punnett square or a probability method to calculate the expected ratios of genotypes and phenotypes, as follows:

Genotypic Ratio
- YYRR: 1/16 or 6.25%
- YYRr: 2/16 or 12.5%
- YyRR: 2/16 or 12.5%
- YyRr: 4/16 or 25%
- yyRR: 2/16 or 12.5%
- yyRr: 2/16 or 12.5%
- yyrr: 1/16 or 6.25%

Note that the genotypic ratio follows the classic 9:3:3:1 ratio of Mendelian inheritance, where the first two numbers (9 and 3) represent the dominant phenotypes and the last two numbers (3 and 1) represent the recessive phenotypes. However, the actual proportions may vary due to chance events, such as random fertilization and small sample sizes.

Phenotypic Ratio
- Yellow Round: 9/16 or 56.25%
- Yellow Wrinkled: 3/16 or 18.75%
- Green Round: 3/16 or 18.75%
- Green Wrinkled: 1/16 or 6.25%

Note that the phenotypic ratio does not follow the 9:3:3:1 ratio exactly, because the two dominant traits (yellow and round) are not completely dominant and may show some blending or incomplete dominance in the heterozygous state (YyRr). This means that some YyRr offspring may have an intermediate or mixed phenotype between the two homozygous states (YYRR and yyrr). However, the overall trend is still that the dominant traits are more common than the recessive traits, and the ratio reflects the relative frequencies of different genotypes and the expression of their alleles.

Therefore, the correct answer to the question is A. 9:3:3:1 ratio of phenotypes, because this is the most accurate description of the expected outcome of self-pollination in plant YyRr. Option B is incorrect because it ignores the phenotypic effects of the genotypes. Option C is incorrect because it assumes equal dominance among all traits, which is not the case. Option D is partially correct but incomplete, as it does not specify which ratios are being referred to.