Concept explainers
Students taking a genetics exam were expected to answer the following question by converting data to a “meaningful ratio” and then solving the problem. The instructor assumed that the final ratio would reflect two gene pairs, and most correct answers did. Here is the exam question:
“Flowers may be white, orange, or brown. When plants with white flowers are crossed with plants with brown flowers, all the F1 flowers are white. For F2 flowers, the following data were obtained:
48 white
12 orange
4 brown
Convert the F2 data to a meaningful ratio that allows you to explain the inheritance of color. Determine the number of genes involved and the genotypes that yield each
(a) Solve the problem for two gene pairs. What is the final F2 ratio?
(b) A number of students failed to reduce the ratio for two gene pairs as described above and solved the problem usingthree gene pairs. When examined carefully, their solution was deemed a valid response by the instructor. Solve the problem using three gene pairs.
Want to see the full answer?
Check out a sample textbook solutionChapter 4 Solutions
Essentials of Genetics (9th Edition) - Standalone book
- A cross was performed using Drosophila melanogaster involving a female known to be heterozygous for both ebony body and sepia eyes and a male known to be homozygous wild type male. The resulting progeny were allowed to mate with one another to produce the data set. Three repetitions of the experiment were conducted. The following data were produced from the crosses. Test these data to determine if they are significantly different from the expected phenotypic ratio. Use the 5% level of significance. Your answer should include the hypothesized cross in genotypes, the Chi-squared value, the critical value and whether you reject or do not reject for each experiment. Wild eye Wild body – 112, Wild eye Ebony body – 40, Sepia eye Wild body – 35, Sepia eye Ebony body – 11arrow_forwardREad and analyzed the following genetic problem. Show complete solution (Genotypes of P, Punnet Square and GR,PR). 1. In the garden peas, green pod color is dominant over yellow pods. Also, round seed shape is dominant over wrinkled seed. Cross fertilization was done between a pea that is homozygous dominant for pod color with heterozygous round shape and another pea that is heterozygous for both pod color and seed shape. Determine the genotypic and phenotypic ratio of teh offspring.arrow_forwardThis question deals with Mendelian Genetics. Read each part carefully before you answer it. In the following questions, assume green pea pods are dominant over yellow pea pods. a) If a pea plant that is Heterozygous for pod color is crossed with a pea plant with yellow pods, what do you expect to see in the offspring (the f1 generation)? Specifically, what genotypes, what phenotypes, and in what ratios? (Use G for the green pod gene and g for the yellow pod gene.) (It is usually helpful to write out all the possible genotypes and give the phenotype for each genotype before answering the specific question.)arrow_forward
- A 3-inch plant was crossed with a 15-inch plant, and all F1 plants were 9 inches. The F2 plants exhibited a “normal distribution,” with heights of 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 inches. (a) What ratio will constitute the “normal distribution” in the F2? (b) What will be the outcome if the F1 plants are testcrossed with plants that are homozygous for all nonadditive alleles?arrow_forwardYou are studying three linked genes in snapdragons. The flower color locus is in the center. There are 8.3 cM between the flower color locus and the plant height locus. There are 12.4 cM between the flower color locus and the leaf type locus. The coefficient of coincidence is 0.8. Pure-breeding tall, red-flowered plants with fuzzy leaves were crossed to pure-breeding dwarf, blue-flowered plants with smooth leaves. The F1 were testcrossed. Calculate the proportion of the testcross progeny that are expected to have red flowers and fuzzy leaves. Round properly to 4 decimal digits. Answer:arrow_forwardA series of three-point testcrosses is made to determine the genetic map order of seven linked allele pairs: A/a, B/b, G/g, H/h, Q/q, R/r, and Y/y.From each cross between a triply heterozygous parent listed below, two recombinant classes were noticed as the least frequent among all 8 progeny classes, and are listed at the right in the table. A. For each testcross write the genotype of the F1 heterozygous parent. F1 Parental Phenotype Least frequent F2 Phenotype 1.AHB&ahb AHb & ahB 2.RYh&ryH RYH & ryh 3.BhY&bHy Bhy & bHY 4.qYB&Qyb qYb & QyB 5.AbQ&aBq Abq & aBQ 6.ghR&GHr ghr & GHR B. Write the unified map order of these genes, showing your reasoning.arrow_forward
- ) You are performing a dihybrid cross with a strain of flies that is ebony (e) and a strain that is pink (p). The results of the F2 are shown below. Use x? test to help you determine if e and p are linked (Note: refer to Table I for chi-square table). Number 1827 Phenotype + p 424 e + 386 e p 298 Genetic map is the relative positions of genetic markers on a chromosome. Explain the rationale behind genetic mapping.arrow_forwardPurebred wrinkled, green-seeded pea plants were crossed with purebred round, yellow-seeded plants. The F1, all of which had round and yellow seeds, were then self-crossed resulting in the following F2: 172 plants with round and yellow seeds, 55 plants with round and green seeds, 58 plants with wrinkled and yellow seeds, and 15 plants with wrinkled and green seeds. Calculate the chi-square value and determine the p-value range. Which of the following are the correct chi-square values, p-value range, and whether you would accept or reject the hypothesis that these results are consistent with Mendelian predictions?arrow_forwardE. W. Lindstrom crossed two corn plants with green seedlings and obtained the following progeny: 3583 green seedlings, 853 virescentwhite seedlings, and 260 yellow seedlings . Q. Explain how color is determined in these seedlings.arrow_forward
- pt pt PT PPTt purple tall PpTt purple tall Pt Pptt purple white Pptt purple white Using any two plants resulting from your test cross (even two of the same genotypes if you would prefer), perform a second cross. Provide a Punnett square demonstrating this dihybrid cross.What are the ratios for each genotype in the resulting offspring? What are the ratios for each phenotype? Your answer should clearly indicate the genotype and phenotype each portion of the ratio is referring toarrow_forwardIn a cross between a 29cm plant and a 20cm plant what would be the genotypes giving the smallest number of different phenotypes? specify the phenotypes observed. (6 genes and 12 alleles involved)arrow_forwardTwo true-breeding varieties of maize, one 11 cm high and the other 47 cm high were crossed and the resultant F1 hybrids were then crossed to generate the F2. In the F2 there were a total of 13,923 plants with a continuous variation in heights between the two extremes and with only 3 plants as large as 47 cm high and 5 plants of 11 cm high. In a cross between a 29cm plant and a 20cm plant what would be the genotypes giving the smallest number of different phenotypes? specify the phenotypes observed.arrow_forward
- Concepts of BiologyBiologyISBN:9781938168116Author:Samantha Fowler, Rebecca Roush, James WisePublisher:OpenStax College