Pearson eText Genetic Analysis: An Integrated Approach -- Instant Access (Pearson+)
3rd Edition
ISBN: 9780135564172
Author: Mark Sanders, John Bowman
Publisher: PEARSON+
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Chapter 19, Problem 11P
In selective breeding experiments, it is frequently observed that the strains respond to artificial selection for many generations, with the selected
a. What is the genetic explanation for the plateau phenomenon?
b. Once a plateau has been reached, is the heritability of the trait very high or is it very low? Explain.
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For each of the following characteristics, indicate whether it would be considered a discontinuous characteristic or a quantitative characteristic. Briefly justify your answer. a. Kernel color in a strain of wheat, in which two codominant alleles segregating at a single locus determine the color. Thus, there are three phenotypes present in this strain: white, light red, and medium red. b. Body weight in a family of Labrador retrievers. An autosomal recessive allele that causes dwarfism is present in this family. Two phenotypes are recognized: dwarf (less than 13 kg) and normal (greater than 23 kg). c. Presence or absence of leprosy. Susceptibility to leprosy is determined by multiple genes and numerous environmental factors. d. Number of toes in guinea pigs, which is influenced by genes at many loci. e. Number of fingers in humans. Extra (more than five) fingers are caused by the presence of an autosomal dominant allele.
The mean and standard deviation of plant height from two rice plants (P1 and P2) and their progeny (F1 and F2) and a backcross generation (P1 x F1) are shown below.
Interpret the CV results from each population.
To locate genes associated with quantitative traits, geneticists often use QTL mapping (see the introduction to this chapter). To carry out QTL mapping, a first step is crossing two strains that differ in a quantitative trait, such as a strain of corn with high oil content and a strain with low oil content. The F1 progeny of this cross are then interbred or backcrossed to produce an F2 generation. Researchers then look for statistical associations between genetic markers and the value of the quantitative trait (e.g., oil content) in the F2 generation. Why do the geneticists look for statistical associations in the F2 plants? Why not use the F1 progeny?
Chapter 19 Solutions
Pearson eText Genetic Analysis: An Integrated Approach -- Instant Access (Pearson+)
Ch. 19 - Which of the following traits would you expect to...Ch. 19 - 19.2 For the traits listed in the previous...Ch. 19 - Compare and contrast broad sense heritability and...Ch. 19 - 19.4 In a cross of two pure-breeding lines of...Ch. 19 - 19.5 Describe the difference between continuous...Ch. 19 - Prob. 6PCh. 19 - 19.7 Provide a definition and an example for each...Ch. 19 - 19.8 What is a random sample, and why can a random...Ch. 19 - 19.9 Why is heritability an important phenomenon...Ch. 19 - 19.10 Three pairs of genes with two alleles each (...
Ch. 19 - 19.11 In selective breeding experiments, it is...Ch. 19 - 19.12 Two inbred lines of sunflowers produce...Ch. 19 - What is quantitative trait locus (QTL)? Suppose...Ch. 19 - 19.14 In Nicotiana, two inbred strains produce...Ch. 19 - 19.15 Suppose the length of maize ears has narrow...Ch. 19 - In a line of cherry tomatoes, the average fruit...Ch. 19 - 19.17 Two purebreeding wheat strains, one...Ch. 19 - Prob. 18PCh. 19 - During a visit with your grandparents, they...Ch. 19 - 19.20 An association of racehorse owners is...Ch. 19 - Prob. 21PCh. 19 - Suppose a polygenic system for producing color in...Ch. 19 - New Zealand lamb breeders measure the following...Ch. 19 - Cattle breeders would like to improve the protein...Ch. 19 - In human gestational development, abnormalities of...Ch. 19 - The children of couples in which one partner has...Ch. 19 - Answer the following in regard to multifactorial...Ch. 19 - 19.28 Suppose the mature height of a plant is a...Ch. 19 - A three-gene system of additive genes (A, B, and...Ch. 19 - 19.30 Congenital dislocation of the hip is a...Ch. 19 - A total of 20 men and 20 women volunteer to...
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- Please explain the correct optionarrow_forwardThe mean and standard deviation of plant height from two rice plants (P1 and P2) and their progeny (F1 and F2) and a backcross generation (P1 x F1) are shown below. Compare the sample variances of P1 and P2. Account for any differences. Similarly, compare the sample variances of the F1 and F2 generations, and account for any differences. Give the possible causes of variation in each generation.arrow_forwardCompare the sample variances of P1 and P2. Account for any differences. Similarly, compare the sample variances of the F1 and F2 generations, and account for any differences. Give the possible causes of variation in each generation.arrow_forward
- Assume a large population has two alleles, B and b, for a particular trait that displays a normal pattern of Mendelian inheritance. If 49% of the population displays the recessive phenotype for this trait.. a. What percent of the population would be heterozygous (Bf)? b. What percent of the population would be homozygous dominant (BB)? c. What percent of the population would display the dominant phenotype? d. What is the frequency of the recessive allele (b) expressed as a percentage? e. What is the frequency of the dominant allele (B) expressed as a percentage? Place the number in the space provided without any other symbols. MEarrow_forwardIn a hypothetical population, matings involving two individuals heterozygous for the phenylketonuria allele on chromosome 12 result in 10% of the offspring showing the effects of the disease. This percentage arises because: A. the trait has pleiotropic effect B. the trait assorts independently C. the trait has low expressivity D. the trait has only partial penetrance E. the trait is sex-influencedarrow_forwardA particular breed of dog can have long hair or short hair. A second trait involves the texture of the hair. The twovariants are wiry or straight hair. A cross between a pure-breeding long, straight haired dog and a pure-breedingshort, wiry haired dog produced F1 dogs with long, wiry hair.a. Assign symbols to the alleles of both loci using convention. Indicate the dominance relationship at each locus.b. Determine the genotypes of the parental dogs involved in the crosses below by analysing the phenotypes oftheir offspring Parents Offspring Long, wiry x long, wiry ¾ long, wiry : ¼ short, wiry Short, wiry x long, wiry 3/8 short, wiry : 1/8 short, straight : 3/8 long, wiry : 1/8 long, straightarrow_forward
- Explain the possible reasons for the observed differences in the sample means. Account for the differences in the sample means of P1 and P2. Similarly, account for the differences in the sample means of the F1 and F2. Compare the difference in the parental generations with that in the filial generations.arrow_forwardMany inheritance patterns in traits, especially continuous ones, cannot be accounted for by Mendelian genetics. Why might this be? Select all that apply. A. The trait might not be controlled by any genes. B. The trait might have multiple genes that control it. C. There might not be any alleles that result in the trait. D. There might be more than two alleles that result in the trait. E. Two alleles might be codominant for the trait. F. The trait might not have any codominant alleles.arrow_forwardSuppose a geneticist is using a three-point test cross to map three linked rabbit morphology and behavioral mutations called si, sf, and H. The gene si is associated with the silky fur phenotype, and sf is associated with the short-footed phenotype. Both si and sf are recessive mutations with respect to wild type. H is a dominant mutation that confers the hyper phenotype. The geneticist first crosses true-breeding hyper rabbits to true-breeding silky fur, short-footed rabbits. Next, the geneticist backcrosses the F₁ progeny to the silky fur, short-footed parents, and obtains the results reported in the table. Phenotype hyper silky fur, short-footed short-footed silky fur, hyper silky fur short-footed, hyper silky fur, short-footed, hyper wild type Place the genes in the correct order in the chromosome. LLIIN HEL H Number 815 807 175 169 4 5 27 29 Answer Bank si sfarrow_forward
- In an experiment focusing on weight gain between ages 3 and 6 weeks in mice, the difference in mean phenotype between two strains was 17.6 grams and the genotypic variance was estimated as 0.88. Estimate the minimum number of genes affecting this trait.arrow_forwardWhich of the following statements best describe the equation P = G + E + (G X E)?* a. The phenotype is the sum of the genotype and the environment. b. The phenotype of an organism is determined by its genetic traits. c. The phenotype is the total characteristics displayed by an organism that results from the expression of the genes as well as the influence of environmental factors. d. The phenotype is the observable and measurable characteristics of an organism as a result of the interaction of the genes of the organism, environmental factors, and random variation.arrow_forwardThe normal color of snapdragons is red. Some pure lines showing the variations of flower color have been found. When these lines were crossed, they gave the results attached. A. From the data given, determine if alleles of one, two, or three genes are generating these traits and why? B. Define the results of cross #5 with gene symbols and a complete explanation of ratios and any relevant genetic terms.arrow_forward
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