What cross will produce the most pink-flowered plants ?
The correct answer and explanation is :
The cross that will produce the most pink-flowered plants is a cross between two heterozygous (Rr) plants, where R (red) and r (white) exhibit incomplete dominance.
Correct Answer:
Rr × Rr (heterozygous pink × heterozygous pink)
Explanation:
- Understanding Incomplete Dominance
In incomplete dominance, neither allele is completely dominant over the other. Instead of one allele masking the effect of the other, a heterozygous genotype results in a blended or intermediate phenotype. In this case:
- RR (homozygous red) produces red flowers.
- rr (homozygous white) produces white flowers.
- Rr (heterozygous) produces pink flowers due to the blending of red and white alleles.
- Punnett Square Analysis
Crossing two heterozygous pink-flowered plants (Rr × Rr) results in the following combinations: Parental Alleles → R r R RR (Red) Rr (Pink) r Rr (Pink) rr (White) This produces the following phenotypic ratio:
- 1 RR (Red)
- 2 Rr (Pink)
- 1 rr (White)
- Maximum Pink-Flowered Plants
From the above ratio, 50% (2 out of 4) of the offspring will have pink flowers. This is the highest possible proportion of pink-flowered plants in a simple monohybrid cross. - Why Not Other Crosses?
- RR × RR → All red
- rr × rr → All white
- RR × rr → 100% pink, but fewer overall when compared to Rr × Rr crosses in larger populations
Thus, the Rr × Rr cross produces the highest number of pink-flowered plants in a given population.