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Ch. 5 - Chromosome Mapping in Eukaryotes
Chapter 5, Problem 13

As in Problem 12, flower color may be red, white, or pink, and flower shape may be personate or peloric. For the following crosses, determine the P₁ and F₁ genotypes:

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1
Step 1: Identify the alleles involved in determining flower color and shape.
Step 2: Determine the genotypes of the P₁ generation based on the given phenotypes.
Step 3: Use a Punnett square to predict the possible genotypes of the F₁ generation.
Step 4: Analyze the Punnett square results to determine the phenotypic ratios in the F₁ generation.
Step 5: Summarize the genotypes and phenotypes of the F₁ generation based on the Punnett square analysis.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Genotype

A genotype refers to the genetic constitution of an organism, specifically the alleles it possesses for a particular trait. In the context of flower color and shape, the genotype will determine the specific combinations of alleles that result in red, white, pink flowers, or personate and peloric shapes. Understanding genotypes is crucial for predicting the phenotypic outcomes of genetic crosses.
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Phenotype

Phenotype is the observable physical or biochemical characteristics of an organism, determined by both its genotype and environmental influences. In this case, the phenotypes include the colors of the flowers and their shapes. Recognizing the relationship between genotype and phenotype is essential for interpreting the results of genetic crosses.
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Mendelian Inheritance

Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which describe how traits are passed from parents to offspring through dominant and recessive alleles. This concept is fundamental for predicting the genotypes of the P₁ (parental generation) and F₁ (first filial generation) in genetic crosses, as it helps to understand how different traits segregate and assort independently.
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Related Practice
Textbook Question
In a series of two-point mapping crosses involving five genes located on chromosome II in Drosophila, the following recombinant (single-crossover) frequencies were observed: pr–adp 29% pr–vg 13 pr–c 21 pr–b 6 adp–b 35 adp–c 8 adp–vg. 16 vg–b. 19 vg–c 8 c–b. 27 In another set of experiments, a sixth gene, d, was tested against b and pr: d–b 17% d–pr 23% Predict the results of two-point mapping between d and c, d and vg, and d and adp.
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Textbook Question
Three gene pairs located on separate autosomes determine flower color and shape as well as plant height. The first pair exhibits incomplete dominance, where the color can be red, pink (the heterozygote), or white. The second pair leads to personate (dominant) or peloric (recessive) flower shape, while the third gene pair produces either the dominant tall trait or the recessive dwarf trait. Homozygous plants that are red, personate, and tall are crossed to those that are white, peloric, and dwarf. Determine the F₁ genotype(s) and phenotype(s). If the F₁ plants are interbred, what proportion of the offspring will exhibit the same phenotype as the F₁ plants?
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Textbook Question
Two different female Drosophila were isolated, each heterozygous for the autosomally linked genes b (black body), d (dachs tarsus), and c (curved wings). These genes are in the order d–b–c, with b being closer to d than to c. Shown here is the genotypic arrangement for each female along with the various gametes formed by both: Identify which categories are noncrossovers (NCOs), single crossovers (SCOs), and double crossovers (DCOs) in each case. Then, indicate the relative frequency in which each will be produced.
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Textbook Question
In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table. Phenotype Offspring sc s v 314 + + + 280 + s v 150 sc + + 156 sc + v 46 + s + 30 sc s + 10 + + v 14 No determination of sex was made in the data. Using proper nomenclature, determine the genotypes of the P₁ and F₁ parents.
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Textbook Question
In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table. Phenotype Offspring sc s v 314 + + + 280 + s v 150 sc + + 156 sc + v 46 + s + 30 sc s + 10 + + v 14 No determination of sex was made in the data. Determine the sequence of the three genes and the map distances between them.
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Textbook Question
In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F₁, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F₂ generation, and 1000 offspring were counted, with the results shown in the following table. Phenotype Offspring sc s v 314 + + + 280 + s v 150 sc + + 156 sc + v 46 + s + 30 sc s + 10 + + v 14 No determination of sex was made in the data. Are there more or fewer double crossovers than expected?

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