Final answer:
In Mendelian genetics, a monohybrid cross between two true-breeding parents results in monohybrid offspring with a genotypic ratio of 1:2:1, and, in the case of incomplete dominance, this mirrors the phenotypic ratio, as seen in the pink offspring from red and white four-o'clock flowers. A Punnett square is used to predict these ratios.
Step-by-step explanation:
In Mendelian genetics, various types of crosses can be performed, but when considering a monohybrid cross where there is one characteristic difference between two true-breeding parents, the resulting offspring are termed monohybrids. For instance, in the crossing of true-breeding four-o'clock flowers where red (RR) is crossed with white (rr), all the offspring are pink (Rr), displaying incomplete dominance. Therefore, the genotype of the F1 generation offspring would be heterozygous Rr. This heterozygous self-cross would yield the genotypic ratio of 1:2:1 for RR:Rr:rr, and computationally, the legitimate phenotypic ratio for red:pink:white flowers would be 1:2:1 as well.
A Punnett square facilitates predicting the ratio of genotypic combinations. By utilizing this approach, we can determine that a self-cross of Rr heterozygotes would result in offspring with a 25% chance of being RR, a 50% chance of being Rr, and a 25% chance of being rr. This underscores a fundamental concept in Mendelian inheritance patterns: the 1:2:1 genotypic ratio aligns with a 3:1 phenotypic ratio when observing dominantly inherited traits, although in the case of incomplete dominance such as in four-o'clock flowers, the phenotypic ratio mirrors the genotypic one.