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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Students have asked these similar questions
Consider the recombination frequencies data below from a series of two-point crosses that were carried out for genes found at seven loci
(a, b, c, d, e, f, and g). Use this data to answer the following questions. The seven genes above are found on how many linkage groups?
Loci
a and b
a and c
a and d
a and e
a and f
a and g
b and c
b and d
b and e
b and f
b and g
a. 7 linkage groups
b. 5 linkage groups
c. 4 linkage groups
O d. 3 linkage groups
% Recombination
50
50
50
50
50
50
50
50
50
29
11
Loci
c and d
c and e
c and f
c and g
d and e
d and f
d and g
e and f
e and g
fand g
% Recombination
29
41
50
50
12
50
50
50
50
18
(1)
Two linked loci have a recombination frequency of 5%. A series of crosses is performed. The P generation includes an individual that is homozygous dominant for trait 1 and homozygous recessive for trait 2. The second individual is homozygous recessive for trait 1 and homozygous dominant for trait 2. The F1 generation is crossed with individuals that are homozygous recessive for both traits. If 400 F2 offspring are produced, how many offspring with each phenotype are expected? Fill in the table below with your answers.
Phenotype
Number of Offspring Predicted
Recessive 1, Recessive 2
Dominant 1, Dominant 2
Recessive 1, Dominant 2
Dominant 1, Recessive 2
Total offspring
400
For the results above, determine which phenotypes are parental and which are recombinant.
Phenotype
Parental or Recombinant?
Dominant 1, Dominant 2
Recessive 1, Dominant 2
Recessive 1, Recessive 2
Dominant 1, Recessive 2
In letter B: If the map distance equals the number of recombinant/total of offspring, wouldn't it be 24/806 x 100? Wouldn't we add both recombinants?
Can you explain letter C? I don't grasp that concept well.
And since I'm using my question already, would you be able to answer D.
Thank you!
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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