Concept explainers
When working out genetics problems in this and succeeding chapters, always assume that members of the P1 generation are homozygous, unless the information or data you are given require you to do otherwise.
HOW DO WE KNOW?
In this chapter, we focused on the Mendelian postulates, probability, and pedigree analysis. We also considered some of the methods and reasoning by which these ideas, concepts, and techniques were developed. On the basis of these discussions, what answers would you propose to the following questions:
(a) How was Mendel able to derive postulates concerning the behavior of “unit factors" during gamete formation, when he could not directly observe them?
(b) How do we know whether an organism expressing a dominant trait is homozygous or heterozygous?
(c) In analyzing genetic data, how do we know whether deviation from the expected ratio is due to chance rather than to another, independent factor?
(d) Since experimental crosses are not performed in humans, how do we know how traits are inherited?
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Essentials of Genetics (9th Edition) - Standalone book
- Genetic Problems Read the following genetic problems, and then complete the activities and questions for each problem 1. In the pea plant, the green pod color allele is dominant to the yellow pod color allele. o Set-up a monohybrid cross between a pea plant that is heterozygous and a true-breeding yellow pod pea plant. o What percentage of the offspring produced from this cross would you expect to have yellow pods? 2. Within a mouse population, the black fur allele (B) is dominant to the white fur allele (b) and the short whisker allele (S) is dominant to the ngs long-whisker allele (s). o A heterozygous black-furred short-whiskered mouse is crossed with a homozygous white-furred long-whiskered mouse. o What percentage of the offspring will be black-furred with long whiskers? 3. A physician is examining the blood types of children from a family. o Child 1 has blood type AB, Child 2 has blood type B, Child 3 has blood type B, and Child 4 has blood type A. o Based on the phenotypes of…arrow_forwardQuestion: On the basis of Mendel's hypothesis and observations, predict the results from the following crosses in garden peas: (a) a tall (dominant and homozygous) variety crossed with a dwarf variety: (b) the progeny of (a) selfed; (c) the progeny from (a) crossed with the original tall parent; (d) the progeny from (a) crossed with the original dwarf-parent variety.arrow_forwardRequired information A single-factor cross is one in which the inheritance of only one character and its associated genotypes are followed. Punnett squares are often used to predict the outcomes of simple genetic crosses. Based on Mendel's laws, the genotypes of the parents can be used to predict the genes in their gametes and the resulting progeny. A Punnett square enables you to predict the types of offspring the parents are expected to produce and in what proportions. Sickle cell anemia is a recessive trait in humans. In a cross between two parents who are heterozygous for the gene, what are the gamete possibilities of the parer Mother's gamete possibilities Father's gamete possibilities of 19 Show All MacBook Air 田arrow_forward
- PLease help, double and triple check your answers, im using this to study, these questions are NOT graded they are PRACTICE problems. Please help with all 4 parts of this question!!!!!!! A. Your maternal grandpa is colorblind but both your mom and dad are not affected. What are the chances of your sister being colorblind? What are the chances of your brother being colorblind? (Colorblindness is X-linked recessive) B. Regarding the problem above, if your sister’s husband is colorblind, what are the chances that their first son will be colorblind? C. Two genes, A and X, exhibit incomplete linkage. The frequency of each parental gamete (AX and ax) is 45%. What is the approximate frequency of the Ax gamete? D. There are three genes located in the gene order A--B--C on a chromosome. Would you expect the recombination frequency to be higher between A and B or A and C?arrow_forwardQuestion: This is a normal 3 point test cross, except that instead of regular phenotypes, you are looking at DNA markers on a gel. One parent, according to the gel, is heterozygous at each marker. The other parent is homozygous for each marker. (Again, this means it is a test cross: AaEeHh x AAEEHH --but don't be confused by that, because these are not "dominant" and "recessive" per se; the phenotype is just a band on a gel). For each offspring, figure out its genotype (homozygous or heterozygous for each gene. Then, figure that one parent made only AEH gametes, so you can cross that out if it helps.) Then treat it pretty much the same as a 3 point test cross.arrow_forwardProblem 4: Here are four human pedigrees. The black symbols represent an abnormal phenotype inherited in a simple Mendelian manner. 2 SODOCTO 566 7 588 166 560 a. For each pedigree, state whether the abnormal condition is dominant or recessive. Try to state the logic behind your answer. b. For each pedigree, describe the genotypes of as many persons as possible.arrow_forward
- Application Instructions: Before Mendel and his results were fully accepted, there were many theories that were proposed that tried to explain how traits were passed on from one generation to another. In the space provided, list down the important points of each theory. Hippocrates': Brick and Mortar Theory Aristotle: Hereditary Elements in Blood Darwin: Theory of Pangenesisarrow_forwardSample problems related to non Mendelian inheritanceRead, analyze and answer completely the following problems: 1. Explain why it is possible for the proband in the following pedigree to have children of blood types A, B, and AB. Considering epistatic genes, what are the possible genotypes of II-2? 2. Agouti (A) is wild type and produces alternating bands of pigment on each hair. Black (a) is recessive to agouti. A mutation on gene B (recessive b) can eliminate all color. In a cross between agouti (AABB) and albino (aabb) mice, what genotypes, phenotypes, and proportions are expected in the offspring in F1 and F2 generations?arrow_forwardQuestion:- 3. Wild type Drosophila has red eyes and gray body*. Autosomal recessive mutations sepia (se) and ebony (e) modify the eye and body color, respectively. What kind of a cross (or crosses) can you set up to determine whether the two genes are linked? You have several lines to choose from: a pure-breeding wild type line (where alleles for both, sepia and ebony are wild type), a double homozygous recessive line, a pure breeding sepia mutant line and a pure breeding ebony mutant line. You don’t have to use all of them. (a) Write down the cross (or crosses, if necessary) which will allow you to determine linkage; include genotypes of both crossed individuals (b) What kind of results (offspring) do you expect if the two genes are linked? (c) What kind of results (offspring) do you expect if the two genes are not linked? For (b) and (c), state the phenotypes, genotypes and numbers.arrow_forward
- The Meeting Sarah stared blankly at the blue paisley wallpaper. Her husband Mike sat by her side, bending and unbending a small paper clip. “Sarah and Michael, it’s good to meet you,” welcomed the genetic counselor, as she entered the room. “I apologize for being late, but I was just meeting with another couple. Let’s see, you’d like to have a child, but you’re concerned because of your family history of cystic fibrosis.” “Yes,” Sarah replied softly. “Mike and I met at a CF support group meeting a few years ago. He had a younger brother who died of cystic fibrosis, and I had a younger sister. We saw the painful lives they had—difficulty breathing, the constant respiratory infections. Although the treatments for CF are better now, we just don’t know if we can…” she trailed off. “I can certainly understand your concern,” the genetic counselor responded sympathetically. “That’s where I hope to help, by providing as much information and advice as I can. I’m glad that you came to see me…arrow_forwardI need help solving this : In humans, the X chromosome is large in comparison to the Y chromosome. The X chromosome carries information for many traits that aren't related to the sex of the individual. Alleles carried only by the X chromosome are said to be X-linked (or some-times, sex-linked). Some of the alleles on the tiny Y chromosome appear to have no counterparts on X. These Y-linked alleles code for traits that are found only in males. Among the X-linked traits are a number of recessive genetic disorders. One of these is hemophilia, the inability to produce proteins necessary for blood clotting. Hemophiliacs can bleed to death from relatively minor cuts or bruises. Historical records dating back thousands of years mention the inheritance pattern of hemophilia. Among the ancient Hebrews, sons born to women with a family history of hemophilia were excused from circumcision. Hemophilia was common during the 1800s in the royal families of Europe, whose members often intermarried.…arrow_forwardQUESTION 6 In Drosophila, sepia eyes (se) and stubble bristles (sb) are recessive to the wildtype eyes and bristles (se* and sb+). A female heterozygous for both genes was test crossed to a male homozygous recessive for both genes. The progeny of this cross are given below: Phenotypes wildtype eyes and wildtype bristles (set, sbt) # of Progeny 334 widltype eyes and stubble bristles (set, sb) 162 sepia eyes and wildtype bristles (se, sb+) 158 sepia eyes and stubble bristles (se, sb) 346 What is the genetic distance (in map units) between these two genes? Are the alleles in the heterozygous female in the cis (coupling) or trans (repulsion) conformation? Are the two genes in this problem unlinked, completely linked or incompletely linked?arrow_forward
- Human Heredity: Principles and Issues (MindTap Co...BiologyISBN:9781305251052Author:Michael CummingsPublisher:Cengage Learning