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.
can you explain step by step how you got these answers? I have tried many ways and I'm still not understanding it.
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
(a) To suggest genotypes for the white, yellow, and green phenotypes, we can use a simplified allele notation. Let's denote the dominant allele for white fruits as "W," the dominant allele for yellow fruits as "Y," and the dominant allele for green fruits as "G."
Based on the given information, we know that the cross between yellow (YY) and white (WW) parents produced an F1 generation consisting of all white-fruited plants. From this, we can infer that the yellow allele (Y) is recessive to the white allele (W), meaning that the white phenotype is homozygous dominant (WW) and the yellow phenotype is homozygous recessive (yy).
Now, looking at the F2 generation, we know that the F1 generation (WW x yy) produced an F2 generation segregating in a ratio of 12 white: 3 yellow: 1 green. This ratio suggests that the green phenotype is the result of a different allele and that it is also recessive to the white.
From this, we can deduce the following genotypes for the white, yellow, and green phenotypes:
- White: WW (homozygous dominant)
- Yellow: yy (homozygous recessive)
- Green: gg (homozygous recessive)
(b) Given this information, the genotypes for the P (parental), F1 (first filial), and F2 (second filial) generations of this cross can be determined:
- P generation: Yellow parents (YY) crossed with white parents (WW)
- F1 generation: All white plants (WW) resulted from the cross of Yellow X White.
- F2 generation: Segregates in a ratio of 12 white: 3 yellow: 1 green (WW:WW:WW:WW:WW:WW:WW:WW:WW:WW:WW:WW:yy:yy:yy:gg).
To determine the genotypes of the white, yellow, and green phenotypes in the summer squash, we can use the principles of Mendelian genetics. Let's analyze the information provided step by step to arrive at the genotypes for each phenotype.
(a) Suggest genotypes for the white, yellow, and green phenotypes.
To determine the genotypes, we need to understand the patterns of inheritance in this cross. The cross between yellow (Y) and white (W) parents produced an F1 generation with all white-fruited (WW) plants. From the F2 generation, we observe a segregation ratio of 12 white: 3 yellow: 1 green. This ratio indicates a dominant and recessive relationship between the traits, where white is dominant over both yellow and green.
Based on this information, we can suggest the following genotypes for the phenotypes:
- White phenotype: Homozygous dominant (WW) or heterozygous (Ww)
- Yellow phenotype: Homozygous recessive (yy)
- Green phenotype: Homozygous recessive (yy)
(b) Give genotypes of the P, F1, and F2 of this cross.
To determine the genotypes of the P (parental), F1 (first filial generation), and F2 (second filial generation), we need to consider the observed phenotypes and the genetic principles underlying the inheritance.
From the given information, we know that the cross between yellow (Y) and white (W) parents produced an F1 generation with all white-fruited plants.
Therefore:
- Parental generation (P): Yellow (yy) x White (WW or Ww)
- F1 generation: All white-fruited (WW or Ww)
- F2 generation: Segregating 12 white: 3 yellow: 1 green (WW/Ww: yy/yy: yy/yy)
Please note that without more specific information or the controlled crosses, we cannot precisely determine the genotype of the white-fruited plants in the F1 or the parental generation. The genotypes provided above are possibilities based on the given data.