Genetics: Analysis and Principles
6th Edition
ISBN: 9781259616020
Author: Robert J. Brooker Professor Dr.
Publisher: McGraw-Hill Education
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Chapter 6, Problem 3EQ
Explain the rationale behind a testcross. Is it necessary for one of the parents to be homozygous recessive for the genes of interest? In the heterozygous parent of a testcross, must all of the dominant alleles be linked on the same chromosome and all of the recessive alleles be linked on the homolog?
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In Drosophila, the fruit fly, white eyes are determined by a recessive X-linked gene and the wild-type or normal brick-red eyes are due to its dominant allele. Use symbols of the following types: XrY = a white-eyed male; XRXR = a homozygous normal red female
Show the genotypes and list the phenotypes of the F1 offspring
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a) How many different gametes are possible in the F1generation? What are the genotypes of these gametes?
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What is a reciprocal cross? Suppose that a gene is found as a wildtype (functional) allele and a recessive mutant (nonfunctional)allele. What would be the expected outcomes of reciprocal crossesif a true-breeding normal individual was crossed to a true-breedingindividual carrying the mutant allele? What would be the results ifthe gene is maternally inherited?
Chapter 6 Solutions
Genetics: Analysis and Principles
Ch. 6.1 - 1. Genetic linkage occurs because
a. genes that...Ch. 6.1 - In the experiment by Bateson and Punnett, which of...Ch. 6.2 - Prob. 1COMQCh. 6.2 - Prob. 2COMQCh. 6.2 - 3. For a chi square analysis involving genes that...Ch. 6.3 - Answer the multiple-choice questions based on the...Ch. 6.3 - Answer the multiple-choice questions based on the...Ch. 6.4 - 1. A tetrad of spores in an ascus is the product...Ch. 6.4 - Prob. 2COMQCh. 6.5 - 1. The process of mitotic recombination involves...
Ch. 6 - 1. What is the difference in meaning between the...Ch. 6 - 2. When a chi square analysis is applied to solve...Ch. 6 - 3. What is mitotic recombination? A heterozygous...Ch. 6 - 4. Mitotic recombination can occasionally produce...Ch. 6 - 5. A crossover has occurred in the bivalent shown...Ch. 6 - A crossover has occurred in the bivalent shown...Ch. 6 - A diploid organism has a total of 14 chromosomes...Ch. 6 - If you try to throw a basketball into a basket,...Ch. 6 - 9. By conducting testcrosses, researchers have...Ch. 6 - In humans, a rare dominant disorder known as...Ch. 6 - 11. When true-breeding mice with brown fur and...Ch. 6 - Though we often think of genes in terms of the...Ch. 6 - 13. If the likelihood of a single crossover in a...Ch. 6 - 14. In most two-factor crosses involving linked...Ch. 6 - Researchers have discovered that some regions of...Ch. 6 - 16. Describe the unique features of ascomycetes...Ch. 6 - Figure 6.1 shows the first experimental results...Ch. 6 - In the experiment of Figure 6.6, Stern followed...Ch. 6 - 3. Explain the rationale behind a testcross. Is it...Ch. 6 - 4. In your own words, explain why a testcross...Ch. 6 - Explain why the percentage of recombinant...Ch. 6 - 6. If two genes are more thanapart, how would you...Ch. 6 - 7. In Morgan’s three-factor crosses of Figure 6.3,...Ch. 6 - Two genes are located on the same chromosome and...Ch. 6 - 9. Two genes, designated A and B, are locatedfrom...Ch. 6 - 10. Two genes in tomatoes areapart; normal fruit...Ch. 6 - In the tomato, three genes are linked on the same...Ch. 6 - A trait in garden peas involves the curling of...Ch. 6 - Prob. 13EQCh. 6 - 14. In the garden pea, several different genes...Ch. 6 - A sex-influenced trait is dominant in males and...Ch. 6 - Three recessive traits in garden pea plants are as...Ch. 6 - In mice, a trait called snubnose is recessive to a...Ch. 6 - 18. In Drosophila, an allele causing vestigial...Ch. 6 - 19. Three autosomal genes are linked along the...Ch. 6 - 20. Let’s suppose that two different X-linked...Ch. 6 - Prob. 21EQCh. 6 - In mice, a dominant allele that causes a short...Ch. 6 - 2. In Chapter 3, we discussed the idea that the X...Ch. 6 - Mendel studied seven traits in pea plants, and the...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, biology and related others by exploring similar questions and additional content below.Similar questions
- Consider a couple: a woman who is homozygous for a recessive mutation that causes X-linked colorblindness, and a man with full color vision (he does not carry a copy of the mutation). a) What is the probability that a son of this couple will be colorblind? b) What is the probability that a daughter of the couple will be colorblind?arrow_forwardIn fruit flies, the following X-linked traits are found: white eyes are recessive to red eyes, ebony body is recessive to gray body, and short wings is recessive to long wings. A cross was made between wild-type males with red eyes, long wings, and gray bodies and females with white eyes, short wings, and ebony bodies. Female heterozygote resulting from this cross, which had red eyes, long wings, and gray bodies, were then crossed with males with white eyes, short wings, and ebony bodies. The F2 generation data is obtained below: 1299 white eyes, short wings, ebony bodies 1367 red eyes, long wings, gray bodies 99 white eyes, short wings, gray body 89 red eyes, long wings, ebony bodies 49 white eyes, long wings, ebony bodies 49 red eyes, short wings, gray bodies 1 red eyes, short wings, ebony bodies 1 white eyes, long wings, gray bodies A) Calculate the map distance separating the three genes B) Which gene is in the middle?arrow_forwardIn Drosophila fruit flies, the genes for warped wings (dwp), rumpled bristles (rmp), and pallid wings (pld) are linked. A trihybrid female for all three allleles is crossed with homozygous recessive male for all three alleles and the offspring obtained showed the following phenotypes: 3 pld rmp dwp 428 pld rmp + 427 + + dwp 48 + rmp + 47 pld + dwp 23 pld + + 2 + + + 22 + rmp dwp What is the order and map distance between these three alleles?arrow_forward
- (b) Male cats with a tortoiseshell phenotype do not usually occur. Explain why. A tortoiseshell female was crossed with a black male. Use a genetic diagram to (c) show all the possible genotypes and the ratio of phenotypes expected in the offspring of this cross. Use X to indicate the allele G on an X chromosome. Use XB to indicate the allele B on an X chromosome. Genotypes of offspring Phenotypes of offspring Ratio of phenotypes Page 2 PhysicsAndMaths Tutor.comarrow_forwardIn flies, eye color is a sex-linked trait. Red eyes are dominant (XE) and white eyes are recessive (X). Consider the following 2 cases: 8) The female fly has white eyes and the male fly has red eyes. Figure out the percentage or ratio of possible genotypes and phenotypes of their offspring. Construct a Punnett Square first. Possible genotypes: Possible phenotypes: XE XE: Red Eyes: XE X°: Xe X°: XE Y: White Eyes: Xe Y: 751°Farrow_forwardIn flies, long wings are a dominant trait, and short wings are a recessive trait Medium wings are the heterozygous trait. Based on this information, if a homozygous long-winged fly is crossed with another a heterozygous fly, their offspring will have which percentages for long, medium, and short wings? Assume random chromosome segregation. 17) A) 25% long, 75% medium, 0% short B) 50% long, 25% medium, 25% short C) 50% long, 509% medium, 0% short D) 100% medium. 0% long, 0% shortarrow_forward
- In mice, short hair is dominant over long hair. If a heterozygous shorthaired male is crossed with a heterozygous female, what are the genotypes of the parents?arrow_forwardSuppose you are testing the null hypothesis that the mode of inheritance for a particular disease in elegant cranes is sex-linked recessive. You employ the following crosses, where R is the wild-type allele, r is the disease allele, and Y is Y-chromosome allele (only in males): Parental cross (Affected male with unaffected (carrier) female): rY x Rr. F₁ cross (Unaffected male with affected female): RY x rr. Suppose you perform these crosses at two different research locations. You obtain the following counts in the F2 generation: Location 01 Male, Disease: 200 Male, Wild-type: 225 Female, Disease: 211 Female, Wild-type: 205, Location 02 Male, Disease: 320 Male, Wild-type: 325 Female, Disease: 354 Female, Wild-type: 310 Do you reject or not reject the null hypothesis that the mode of inheritance is sex-linked recessive at each location? The significance level is 0.01. (Hint: when applying the ChiSq goodness of fit test, if the expected value for a row is 0, remove that row and reduce…arrow_forwardVermilion eye color in Drosophila is sex-linked and recessive. What would be the phenotypes of maleand female progenies of a cross between a 6 vermilion female and 6 wild-type (red) male. what is the f1 and f2 generation. if a reciprocal cross is done containing 6 WT females with 6 mutant males what is the F1 and F2 generation. Do they contain the single gene or double gene?arrow_forward
- In guinea pigs, the gene for black coat color is dominant to the gene for white coat color. What will be the genotypic ratio for the cross between two heterozygous parents?arrow_forwardIn humans, the allele for red-green color blindness is X-linked and recessive. An XY man with normal color vision marries a color-blind XX woman who gives birth to a XX color-blind daughter. A] What is the phenotype and genotype ratios possible for a child born to this couple. B] What is the probability that the second XX daughter of this same couple will also be color blind? C] What is the probability that the next child this couple produces together will be a color-blind XY son? D] What can you tell me about the first color-blind daughter born?arrow_forwardThe recessive allele s causes Drosophila to have small wings, and the s+ allele causes normal wings. This gene is known to be X linked. If a small-winged male is crossed with a homozygous wild-type female, what ratio of normal to small-winged flies can be expected in each sex in the F1? If F1 flies are intercrossed, what F2 progeny ratios are expected? What progeny ratios are predicted if F1 females are backcrossed with their father?arrow_forward
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