Question

A gardener wants to breed tulips with specific characteristics.

He knows that the trait of red flowers is controlled by the allele R (RR and
Rr) and the trait of white flowers is controlled by the allele r(rr).
The gardener crosses two tulips from the F1 generation.
Look at the Punnett square to see this cross.
What is the phenotypic ratio that is expected to be seen in the phenotypes of the F2
generation?
3 red : 1 white
2 red: 2 white
1 RR: 2 Rr: 1 rr
3 RR: 1 rr

Answer 1

The phenotypic ratio that is expected to be seen in the phenotypes of the F2 generation is 3:1.

Red 3 and White1

The phenotypic ratio of 3:1 for red and white tulips in the F2 generation can be explained by the Punnett square and the principles of Mendelian inheritance.

The gardener crosses two tulips from the F1 generation, which means both parents are heterozygous for the flower color gene. Their genotype will be Rr, meaning they carry one dominant allele for red (R) and one recessive allele for white (r).

When these two F1 generation tulips are crossed, their gametes will combine in a 2x2 Punnett square. Each parent contributes two gametes, one with R and one with r.

Answer 2

The expected phenotypic ratio for the F2 generation of tulips with the cross of two F1 heterozygous plants (Rr) exhibiting incomplete dominance would be 1 red: 2 pink: 1 white, or a 1:2:1 ratio, not the typical 3:1 Mendelian ratio for a dominant-recessive inheritance.

Step-by-step explanation:

The gardener crossed two tulips from the F1 generation, where the trait of red flowers is controlled by the allele R and the trait of white flowers is controlled by the allele r. Given that the F1 generation results from a cross of two heterozygous parents (Rr), the expected phenotypic ratio in the F2 generation for red and white flowers is 3:1, following Mendelian inheritance patterns. However, the information provided suggests incomplete dominance, with Rr resulting in pink flowers, not red. In this case, the phenotypic ratio would be 1 red: 2 pink: 1 white (1:2:1), not 3 red: 1 white. Therefore, if we are considering incomplete dominance, the correct expected phenotypic ratio for a cross of two pink-flowered plants (Rr x Rr) would be 1 RR (red): 2 Rr (pink): 1 rr (white).

It is important to note that the phenotypic ratio can be different if the traits do not show simple dominant-recessive inheritance, as with incomplete dominance or co-dominance. In this specific scenario, the Punnett square would determine the exact proportions for the F2 generation.