Genetics: Analysis and Principles
6th Edition
ISBN: 9781259616020
Author: Robert J. Brooker Professor Dr.
Publisher: McGraw-Hill Education
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Textbook Question
Chapter 6, Problem 5EQ
Explain why the percentage of recombinant offspring in a testcross is a more accurate measure of map distance when two genes are close together. When two genes are far apart, is the percentage of recombinant offspring an underestimate or overestimate of the actual map distance?
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Explain why the percentage of recombinant offspring in a testcrossis a more accurate measure of map distance when two genes areclose together. When two genes are far apart, is the percentage ofrecombinant offspring an underestimate or overestimate of theactual map distance?
Explain why the value of the recombination frequencybetween any two genes is limited to 50%.
For linkage analysis, a test cross is used rather than a hybrid cross. Why is this essential? Why would a hybrid cross result in incorrect estimates of genetic distance?
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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- Explain why a 50 percent recovery of single-crossover products is the upper limit, even when crossing over always occurs between two linked genes?arrow_forwardIn your own words, explain why a testcross cannot produce more than 50% recombinant offspring. When a testcross does produce 50% recombinant offspring, what does this result mean?arrow_forwardTo build a genetic map, how many types of crosses will be required to perform if you have three genes to map? Explain.arrow_forward
- Please answer fast When setting up crosses to determine map distances, why do geneticists prefer to cross the hybrid individuals to individuals homozygous for the recessive alleles in the cross?arrow_forwardUse the image to observe the results of a cross between a tall pea plant and a short pea plant. What phenotypes and proportions will be produced for the two crosses? P generation Tall Tt Gametes Tt F₁ generation T Fertilization Tt t Tall tt Short Tt Tall tt tt Short Conclusion (a) Short (b) Genotypic ratio 1Tt:1tt Phenotypic ratio 1 tall: 1 short Tall F₁ progeny backcrossed to the short parent Answer Bank one-fourth tall and three-fourths short one-half tall and one-half short three-fourths tall and one-fourth short Tall F₁ progeny backcrossed to the tall parent all tall all shorarrow_forwardUsing Excel produce a plot that shows the decay of D over time (for 50 generations) for four different recombination frequencies: r = 0.5 (independent assortment) r = 0.25 r = 0.1 r = 0.01 *show graph and plot *arrow_forward
- Why are specific alleles of two distant genes more likely to show recombination than those of two closer genes?arrow_forwardWhen a chi square test is applied to solve a linkage problem, explain why an independent assortment hypothesis is proposed.arrow_forwardConsider the genetic map below. (a) In a total of 1000 observed progeny, how many would be expected to be parental, non-recombinant? (b) If the total number of observed double-crossover recombinant progeny is 0, what is the interference? Show step by step work for full credit. A-------10cm-----B—2.5cm----Carrow_forward
- A geneticist determines that the order of four genes on a specific chromosome is CABD because the recombination frequencies were 35% for C-D, 24% for A-D, 23% for B-D, and 10% for A-B. What has the geneticist constructed?arrow_forwardCalculate the recombination frequency from the following data collected from a breeding experiment with butterflies. Parent 1: dihybrid, long legs and blue wings. Parent 2: double recessive, short legs and white wings Offspring: 50 long legs and white wings 200 long legs and blue wings 50 short legs and blue wings 200 short legs and white wings Recombination frequency is: Select one: a. 0.25 (25%) b. 0.10 (10%) c. 0.20 (20%) d. 0.33 (33%) e. 0.50 (50%)arrow_forwardMedaka fish native to Japan have 24 pairs chromosomes, and medaka fish native to China have 23 pairs of chromosomes. In which population of medaka fish would you expect to see more genetic variation in the progeny of a cross? Explain your answer and show your work.arrow_forward
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