d pea plant is crossed with a white-flowered pea plant. All the F1 plants produc
ID: 188839 • Letter: D
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d pea plant is crossed with a white-flowered pea plant. All the F1 plants produce purple flowers. When the F1 plants are allowed to self-fertilize, 62 of the F 2 plants have perple flowers and 19 have the white flowers. What is the genotype of the plants in the F1 generation? b. Pp d. either PP or Pp In tomatoes, red fruit is dominant to yellow. Suppose a tomato plant homozygous for red is crossed with one homozygous for yellow. Determine the appearance of the F1 tomatoes 2. a. 100% red b. 100% yellow C. 50% red and 50% yellow d, 70% red and 25% yellow Can't be determined e. In maize, a dominant allele A is necessary for seed color as opposed to colorless (a). Another gene has a recessive allele w that results in waxy starch, as opposed to normal starch (w). The two genes segregate independently. An AaWw is test crossed. How many phenotypes are there in the F1? 3. b. 2 d. 4 e. In jimsonweed, purple flower (P) is dominant to white (p), and spiny pods (S) are dominant to smooth pods (s). If two dihybrid plants are crossed, what is the frequency of the plant with white flowers and smooth pods? 4. a. 100% b. 1/4 a particular purple- progeny. What In jimsonweed, purple flowers are dominant to white. Self-fertilization of flowered jimsonweed produces 28 purple-flowered and 10 white-flowered proportion of the purple flowered progeny will breed true? 5. a. 100% b. 2/3 c. 1/2 d. 1/3Explanation / Answer
1. b. Pp
The first cross (the cross resulting in F1) between the purple and white flowers yields a heterozygote, which when self-crossed, gives the expected ratio of phenotypes for a test cross, that is 3:1. Therefore, the F1 plant must be a heterozygote.
2. a. 100% red
The same principle as the last question applies, the F1 generation will consist of homozygotes, all of which will be red as it is the dominant allele.
3. d. 4
We have two traits with two different alleles each, which means there are 2 x 2 = 4 different possible phenotypes.
4. c. 1/16
Both plants are heterozygotes. For each recessive trait individually, chances to appear in the F1 generation are 1/4. So for two independently assorting traits, the chances for both traits to be recessive are 1/4 x 1/4 = 1/16
5. d. 1/3
The original purple parent is a heterozygote. The phenotypic ratio of the offsprings is 3:1, while the genotypic ratio must be 1:2:1 for the same cross. When considering only the purple offsprings, the ratio between the true breeding and heterozygote plants will be 1:2 respectively, meaning 1/3 plants will be true breeding and 2/3 will be heterozygotes.
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