In the summer squash, fruits may be white, yellow, or green. In one case, the cross of yellow X white produced an F1 of all white-fruited plants that, when selfed, gave an F2 segregating 12 white: 3 yellow: 1 green. (a) suggest gnotypes for the white, yellow, and green phenotypes. (b) give genotypes of the P, F1, and F2 of this cross.
Biology genetics - bobpursley Friday, January 5, 2018 at 11:04pm
P: Yg x WW yellow x white
F1: YW,YW, gW, gW all white
F2:
first two YY,YW,WW,YW one Yel, 3W
first, third Yg,YW,Wg,WW one Yel, 3W
first, fourth Yg,YW,Wg,WW one Yel, 3W
second third Yg,YW,Wg,WW one Yel, 3 W
third, fourth gg,gW, Wg, WW one g, 3W
now if W dominates to y,g, and Y dominates to g, then I count 15/20 W, 1/20 g, and 3/20 yellow
Now in the F2 above, there were 12/16 W,3/16 Yellow, and 1/16 green Those frequencies look very close to what I laid out.
White 12
Yellow 4
green
I have tried many ways and cannot figure out the answers provided. Could you please show me how you came up with these answers?
Jiskha doesn't have a biology expert at present, but you might be able to find information here:
https://www.khanacademy.org/science/biology
Scroll down to the sections that include "genetics" in their titles and you might find the information you need.
Based on the information provided, we can analyze the results step by step to determine the genotypes for the white, yellow, and green phenotypes and the genotypes of the P, F1, and F2 generations.
a) Genotypes for the white, yellow, and green phenotypes:
- White phenotype: Based on the F1 generation, where yellow X white produced all white-fruited plants, we can conclude that the genotype for the white phenotype is homozygous for the recessive allele. We can represent it as WW.
- Yellow phenotype: In the F2 generation, the yellow phenotype appears in a ratio of 3:16. This suggests that the genotype for the yellow phenotype is heterozygous. We can represent it as YW.
- Green phenotype: In the F2 generation, the green phenotype appears in a ratio of 1:16. This suggests that the genotype for the green phenotype is also heterozygous. We can represent it as Wg.
b) Genotypes of the P, F1, and F2 generations:
- P generation: Given that the cross is between yellow (Yg) and white (WW), we can represent the genotypes of the P generation as Yg x WW.
- F1 generation: The F1 generation resulted in all white-fruited plants. This suggests that all the offspring have the genotype YW (heterozygous for white).
- F2 generation: In the F2 generation, we observe a phenotypic ratio of 12 white: 3 yellow: 1 green. To determine the genotypes, we can consider the possible combinations resulting from the alleles passed down from the F1 generation:
1. YY (yellow) x WW (white) would give YY, YW, YW, and WW (all white). This accounts for the 12 white-fruited plants.
2. Yg (yellow) x WW (white) would give Yg, YW, Wg, and WW, where Yg and Wg represent the yellow and green phenotypes. This accounts for the 3 yellow and 1 green-fruited plants.
Therefore, the genotypes in the F2 generation would be:
- 12 white-fruited plants: YW, YW, YW, YW, YW, YW, YW, YW, YW, YW, YW, and YW.
- 3 yellow-fruited plants: YY, YW, and YW.
- 1 green-fruited plant: YW.
I hope this clarifies how to arrive at these answers. Let me know if you have any further questions!
To understand how the genotypes for the white, yellow, and green phenotypes are determined, we need to analyze the given information step-by-step. Let's break it down:
P: Yg x WW (yellow x white)
This means that the yellow parent has the genotype Yg, and the white parent has the genotype WW.
F1: YW, YW, gW, gW (all white)
When the yellow parent (Yg) is crossed with the white parent (WW), all the resulting offspring in the F1 generation are white. This tells us that white (W) is dominant over yellow (Y) and green (g).
F2: 12 white, 3 yellow, 1 green
In the F2 generation, we observe a phenotypic ratio of 12 white, 3 yellow, and 1 green. To determine the genotypes, we can consider the possible combinations of alleles.
Let's analyze the phenotypic ratios and their corresponding genotypes:
12 white: The possible genotypes for the white phenotypes are WW and Wg (since white must be homozygous dominant or heterozygous).
3 yellow: The possible genotype for the yellow phenotype is Yg (heterozygous).
1 green: The possible genotype for the green phenotype is gg (homozygous recessive).
Now, let's determine the genotypes of the P, F1, and F2:
P: Yellow parent (Yg) and white parent (WW)
F1: All white (WW and Wg)
F2:
- 12 white: WW and Wg
- 3 yellow: Yg
- 1 green: gg
Therefore, the genotypes of the P, F1, and F2 are as follows:
P: Yg x WW
F1: All white (WW and Wg)
F2: 12 white (WW and Wg), 3 yellow (Yg), 1 green (gg)
These genotypes explain the observed phenotypic ratios in the F2 generation.