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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ND STONY BROOK UNIVERSITY LOOSELEAF GENETICS: FROM GENES TO GENOMES
- In a certain species of flowering plants with a diploidgenome, four enzymes are involved in the generationof flower color. The genes encoding these four enzymes are on different chromosomes. The biochemical pathway involved is as follows; the figure showsthat either of two different enzymes is sufficient toconvert a blue pigment into a purple pigment.→ white → green → blue → purpleA true-breeding green-flowered plant is mated with atrue-breeding blue-flowered plant. All of the plants inthe resultant F1 generation have purple flowers. F1plants are allowed to self-fertilize, yielding an F2 generation. Show genotypes for P, F1, and F2 plants, andindicate which genes specify which biochemicalsteps. Determine the fraction of F2 plants with thefollowing phenotypes: white flowers, green flowers,blue flowers, and purple flowers. Assume the greenflowered parent is mutant in only a single step ofthe pathwayarrow_forwardIn a variety of newly discovered rose plant, flowers are either white or red. Two genes were discovered to control flower color. Both genes, A and B, work in tandem in a biochemical pathway, and dominant forms of both genes are required for red flowers. A doubly-homozygous red-flowered plant is crossed with a doubly-homozygous white-flowered plant. The F1 offspring all have red flowers and are self-crossed to produce the F2. Determine the ratios of phenotypes in the F2 generation.arrow_forwardIn corn, male sterility is controlled by maternal cytoplasmic elements. This phenotype renders the male part of corn plants (i.e. the tassel) unable to produce fertile pollen; the female parts, however, remain receptive to pollination by pollen from male-fertile corn plants. However, the presence of a nuclear fertility restorer gene F restores fertility to male-sterile lines. Using the following color-coded circles, simulate the crosses indicated below. Put the illustrations of crosses in the spaces provided. Be sure to include in the labels the genotypes and phenotypes of the offspring in each cross. Big light green circle - male-sterile cytoplasm Big orange circle - male-fertile cytoplasm Small orange circle - FF nucleus Small half-light green-half-orange circle - Ff nucleus Small light-green circle - ff nucleusarrow_forward
- Given the following pathway on the image: G and H are dominant alleles of the two independently assorting genes that produce an enzyme that catalyzes the conversion of one pigment to another, and g and h are recessive alleles that are non-functional. A true-breeding blue plant is crossed with a white plant of genotype ggHH. The F1s are allowed to self-mate. 1. What proportions would you expect in the F2 progeny? 2. Which is the epistatic allele?arrow_forwardTwo plants with white flowers, each from true-breeding strains, were crossed. All the F1 plants had red flowers. When these F1 plants were intercrossed, they produced an F2 consisting of 177 plants with red flowers and 142 with white flowers. (a) Propose an explanation for the inheritance of flower color in this plant species. (b) Propose a biochemical pathway for flower pigmentation and indicate which genes control which steps in this pathway.arrow_forwardIn corn, male sterility is controlled by maternal cytoplasmic elements. This phenotype renders the male part of the corn plants (i.e the tassel) unable to produce fertile pollen; the female parts, however, remain receptive to pollination by pollen from male fertile corn plants. However, the presence of a nuclear fertility restorer gene F restores fertility to male sterile lines Using the cardboard chips, simulate the crosses indicated below. Give the genotypes and phenotypes of the offsprings in each cross, and properly label the nucleus and the cytoplasm of each individual in the cross Legend male sterile cytoplasm Male fertile cytoplasm FF nucleus Ff nucleus ff nucleus A. Male sterile female x FF male Explain the phenotype of the offspring B. Male sterile female x Ff male Explain the phenotype of the offspringarrow_forward
- In a species of tree, seed color is determined by four independently assorting genes: A, B, C, and D. The recessive alleles of each of these genes (a, b, C, and d) produce abnormal enzymes that cannot catalyze a reaction in the biosynthetic pathway for seed pigment. This pathway is diagrammed as follows: A White precursor Yellow ----Orange----- Red --- Blue When both red and blue pigments are present, the seeds are purple. Trees with the genotypes Aa Bb Cc Dd and Aa Bb Cc dd were crossed. (a) What color are the seeds in these two parental genotypes? (b) What proportion of the offspring from the cross will have white seeds? (c) Determine the relative proportions of red, white, and blue offspring from the cross.arrow_forwardIn the fruit fly, dumpy wings (d) and purple eyes (p) are encoded by mutant alleles that are recessive to those that produce wild type traits; long wings (d+) and red eyes (p+). These two genes are on the same chromosome. In a particular lab, two researchers Walt and Jesse crossed a fly homozygous for dumpy wings and purple eyes with a fly homozygous for the wild type traits. The F1 progeny, which had long wings and red eyes, was then crossed with flies that had dumpy wings and purple eyes. Unfortunately, the progeny of this cross somehow escaped. To prevent their other projects from contamination, they decided to spend an exceptionally boring hour in the lab catching and counting the progeny and found the following: long wings, red eyes – 482 dumpy wings, purple eyes – 473 long wings, purple eyes – 23 dumpy wings, red eyes - 22 What is the genetic distance between these two loci? a. 4.5 cM b. 55 cM c. 45 cM d. 49.5 cM e. 4.7 cMarrow_forwardIn 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_forward
- In an intra-species cross performed in mustard plants of two different species (Brassica juncea and Brassica oleracea), a tall plant (TT) was crossed with a dwarf (tt) variety in each of the two species. The members of the F1 generation were crossed to produce the F2 generation. Of the F2 plants, Brassica juncea had 60 tall and 20 dwarf plants, while Brassica oleracea had 100 tall and 20 dwarf plants. Use chi-square analysis to analyze these results.arrow_forwardAssume that diploid plant A has a cytoplasm genetically different from that of plant B. To study nuclear–cytoplasmic relations, you wish to obtain a plant with the cytoplasm of plant A and the nuclear genome predominantly of plant B. How would you go about producing such a plant?arrow_forwardSuppose that a compound attractive to pollinators is produced by a plant in a pathway encoded by genes one (O) and two (T). You have obtained two pure lines of plants, one that produces the compound and one that does not (OOTT and oott, respectively). You cross them to obtain F1 plants that are heterozygous at both loci. (a) Use a branch diagram to visualize the possible outcomes of a cross between two F1 plants. (b) Calculate the expected proportion of offspring that will produce the attractant if this is a case of duplicate recessive epistasis. (c) What is the expected proportion of offspring that will produce attractant if this is a case of duplicate dominance?arrow_forward
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