Concept explainers
In a certain species of flowering plants with a diploid genome, four enzymes are involved in the generation of flower color. The genes encoding these four enzymes are on different chromosomes. The biochemical pathway involved is as follows; the figure shows that either of two different enzymes is sufficient to convert a blue pigment into a purple pigment.
A true-breeding green-flowered plant is mated with a true-breeding blue-flowered plant. All of the plants in the resultant F1 generation have purple flowers. F1 plants are allowed to self-fertilize, yielding an F2 generation.
Show genotypes for P, F1, and F2 plants, and indicate which genes specify which biochemical steps. Determine the fraction of F plants with the following
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Genetics: From Genes to Genomes
- In sweet peas, the synthesis of purple anthocyanin pigment in the petals is controlled by two genes, B and D. What petal color would you expect in a pure breeding plant unable to catalyze the first reaction? Indicate the genotype and phenotype. 2. What petal color would you expect in a pure breeding plant unable to catalyze the second reaction? Indicate the genotype and phenotype. 3. If plants 1 and 2 are crossed, what petal color would the F1 plants have? Indicate the genotype and phenotype. 4. What ratio of purple : blue : white plants would you expect in the F2? Indicate the genotypes, phenotypes, and the F2 phenotypic ratio.arrow_forwardThree enzymes are part of a sequential pathway that produces a pigment that makes flowers red. Each enzyme is the gene product of a different locus. If a trihybrid, heterozygous (+/-) for each of the three loci, is selfed, what fraction of the offspring will not be able to produce the red pigment (and will thus have white flowers)? Express your answer as a number between 0 and 1, rounding to 2 decimal places. For example, if you think 1/4 of the offspring will have white flowers, then answer 0.25arrow_forwardIn the fruit fly, recessive mutations in either of two independently assorting genes, brown and purple, prevent the synthesis of red pigment in the eyes. Thus, homozygotes for either of these mutations have brownish-purple eyes. However, heterozygotes for both of these mutations have dark red, that is, wild-type eyes. If such double heterozygotes are intercrossed, what kinds of progeny will be produced, and in what proportions?arrow_forward
- In a certain plant, the dominant form of gene P codes for purple flowers while the recessive form results in pink flowers. The dominant form of another gene, A, activates the transcription of P, while the recessive form prevents the transcription of P and results in white flowers. A doubly-homozygous purple-flowered plant was crossed with a doubly-homozygous recessive white-flowered plant. The F1 progeny were then self-crossed to generate the F2 generation. Determine the ratios of genotypes and phenotypes for each generation.arrow_forwardA plant geneticist is examining the mode of inheritance of flower color in two closely related species of exotic plants. The first species may have two pure-breeding lines—one produces a distinct red flower; and the other produces flowers with no color at all, or very pale yellow flowers. However, she cannot be sure. A cross of these varieties produces all pink-flowered progeny. The second species exhibits similar pure-breeding varieties; that is, one variety produces red flowers; and the other produces an albino or very pale yellow flower. A cross of these two varieties, however, produces orange-flowered progeny exclusively. Analyze the mode of inheritance of flower color in these two plant species.arrow_forwardIn sweet peas, the given enzymatic pathway result to pigment formation in the flowers: A dihybrid plant is crossed to a white one which is heterozygous at the “C” locus (provided in the image). What is the genotype of the dihybrid plant? What is the genotype of the white plant? What kinds of flowers, colored or white, are to be expected from the cross above? Include the ratio.arrow_forward
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