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 8EQ
Two genes are located on the same chromosome and are known to be
A. If the testcross produces 1000 offspring, what are the predicted numbers of offspring with each of these four genotypes:
B. What would be the predicted numbers of offspring with the four genotypes if the parental generation had been
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In autotetraploid Chinese primrose (Primula sinensis L.), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain.
a. What is the genotype of the Fl1?
b. Show the types of gametes the Fl's may be expected to form and derive the expected proportion of each. Show your solution.
c. What phenotypic ratio of green to red is expected if:
the Fl's are intercrossed? Show your solution.
the Fl's are crossed with red plants? Show your solution.
d. If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the Fl be expected to produce? Derive the expected F2 phenotypic ratio.
In an autotetraploid Chinese primrose (Primula sinensis), the gene controlling stigma color is very near the centromere of the chromosome carrying it. The allele G for green stigma is dominant to g for red stigmas. A homozygous green autotetraploid strain is crossed with a homozygous red autotetraploid strain.
a. What is the genotype of the F1?
b. Show the types of gametes the F1’s may be expected to form and derive the expected proportion of each.
c. What phenotypic ratio of green to red is expected if:
1. The F1’s are intercrossed?
2. The F1’s are crossed with red plants
d. If the G locus were 50 or more map units from the centromere, what types and proportions of gametes would the F1 be expected to produce? Derive the expected F2 phenotypic ratio.
When true-breeding mice with brown fur and short tails (BBtt) were crossed to true-breeding mice with white fur and long tails (bbTT), all the F1 offspring had brown fur and long tails. The F1 offspring were then crossed to mice with white fur and short tails (bbtt). The fur gene and the tail length gene are 7 cM apart.
Part a
Which of the following F2 offspring are recombinant? (Select all that apply.)
a) White fur, short tail
b) Brown fur, long tail
c) You need more information to answer this question.
d) White fur, long tail
e) Brown fur, short tail
Part b
Using the information given in Part a, if there were 400 mice in the F2 generation, how many do you expect would have white fur and long tails?
a) 25
b) 186
c) 14
d) 372
e) 28
f) 75
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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- When true-breeding mice with brown fur and short tails (BBtt)were crossed to true-breeding mice with white fur and long tails(bbTT), all of the F1 offspring had brown fur and long tails. TheF1 offspring were crossed to mice with white fur and short tails.What are the possible phenotypes of the F2 offspring? Which F2offspring are recombinant, and which are nonrecombinant? Whatare the ratios of phenotypes of the F2 offspring if independentassortment is taking place? How are the ratios affected by linkage?arrow_forwardA purple snow pea plant known to be hybrid for three linked genes (a, b, and d) is testcrossed. The progeny phenotypes and frequencies are: +a+ 86 b+d 56 +ad 78 b++ 49 +++ 12 bad 6 ba+ 515 ++d 460 a) Draw the chromosomes of the trihybrid and tester lined mentioned above. b) Give a map of the gene order with distance.arrow_forwardb) You test cross an F1 fish (with genotype BbCc) and obtain 1000 offsprings in F2 generation with the following results: 474 Bbcc, 480 bbCc, 20 BbCc and 26 bbcc.1. Create and fill in a Punnet square for this cross.2. What type of cross is it? 3. Are these loci linked? 4. What are the two parental classes and the two recombinant classes of offspring? 5. What is the percentage of recombination between these two loci? Show your calculations. 6. How many map units apart are they?arrow_forward
- Pigment in mouse fur is only produced when the C allele is present. Individuals of the cc genotype are white. If color is present, it may be determined by the A, a alleles. AA or Aa results in agouti color, while aa results in black coats. (a) What F1 and F2 genotypic and phenotypic ratios are obtained from a cross between AACC and aacc mice? (b) In three crosses between agouti females whose genotypes were unknown and males of the aacc genotype, the following phenotypic ratios were obtained: (1) 8 agouti (2) 9 agouti (3) 4 agouti 8 white 10 black 5 black 10 white What are the genotypes of these female parents?arrow_forwardTwo pure-breeding parents produced a heterozygous female offspring (AaBb) that was then testcrossed with an aabb male. The offspring produced from the testcross included 50 AaBb, 450 Aabb, 450 aaBb, 50 aabb individuals. Describe how you can tell if these two genes are linked or unlinked (What ratio would you expect to see from the testcross if they were not linked?). What were the genotypes of the original parents that produced the heterozygous female? What is the genetic map distance between the two genes?arrow_forwardWild-type mice have brown fur and short tails. Loss of function of a particular gene produces white fur, while loss of function of another gene produces long tails, and loss of function at a third locus produces agitated behavior. Each of these loss of function alleles is recessive. If a wild-type mouse is crossed with a triple mutant, and their F1 progeny is test-crossed, the following recombination frequencies are observed among their progeny. Produce a genetic map for these loci. Brown, short tailed, normal: 955 White, short tailed, normal: 16 Brown, short tailed, agitated: 0 White, short tailed, agitated: 36 Brown, long tailed, normal: White, long tailed, normal: Brown, long tailed, agitated: 46 0 14 White, long tailed, agitated: 933arrow_forward
- You are working with a hypothetical fly and have found color and wing mutants. Preliminary work indicates that the mutant traits are recessive and the associated genes are not sex-linked, but beyond that, you have no information. You first look at 2 genes, each with 2 alleles. "B" or “b" for body color and "W" or "w" for wing surface. The red-body phenotype is dominant to the yellow-body phenotype and smooth wings are dominant to crinkled wings.arrow_forwardThe F1 from a cross of AABB x aabb is testcrossed, resulting in the following phenotypic ratios: AB 308 Ab 190 ab 292 aB 210 (1) what are the genotypes for the listed phenotypes? (2) why aren't the phenotypes in a 1:1:1:1 ratio? (3) what is the frequency of recombination between genes A and B?arrow_forwardYou are trying to determine the relative positions of three genes (A, B and C) that are thought to be on the same chromosome of the organism. You do two dihybrid testcrosses with A being checked in both crosses (so A and B are the genes in one cross and A and C are the genes in the other cross). Based on the results below, which gene (B or C) is closer to A? How can you tell? AаBb aabb Aabb aaBb Total 300 299 202 199 1000 AaCc aacc Аасс aaCc 475 477 25 23 1000arrow_forward
- In a particular organism, the A locus and the D locus are so tightly linked that no crossing over is ever observed between them. If an AADD individual is crossed to an aadd individual, what types of gametes will their double-heterozygote F1 offspring produce and in what proportions? Group of answer choices 25% parental and 75% recombinant gametes 75% parental and 25% recombinant gametes 100% parental and 0% recombinant gametes 50% parental and 50% recombinant gametes 0% parental and 100% recombinant gametesarrow_forwardTo determine the recombination frequency between body color and wing genes in flies, you perform several crosses where you cross an F1 having red body and smooth wings with a yellow-bodied, crinkle-winged fly. You get the following results. What is the distance between the genes for body color and wing surface in map units?arrow_forwardIn com, male sterility is controlled by maternal cytoplasmic elements. However, the presence of a nuclear fertility restorer gene (F_) restores fertility to male sterile lines. a. What are the crosses male sterile female x FF male? Give the genotypes and phenotypes of the offspring in each cross. Explain.arrow_forward
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