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Ch. 7 - Linkage and Chromosome Mapping in Eukaryotes
Klug - Essentials of Genetics 10th Edition
Klug10th EditionEssentials of GeneticsISBN: 9780135588789Not the one you use?Change textbook
All textbooksKlug 10th EditionCh. 7 - Linkage and Chromosome Mapping in EukaryotesProblem 22
Chapter 7, Problem 22

Based on our discussion of the potential inaccuracy of mapping, would you revise your answer to Problem 22? If so, how?

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1
Step 1: Review the original answer to Problem 22 carefully, noting the genetic map distances and recombination frequencies that were calculated or inferred.
Step 2: Understand the concept of mapping inaccuracies, which often arise due to factors like interference, double crossovers, or limitations in detecting recombination events, as discussed in Figure 5.12.
Step 3: Consider how these inaccuracies might affect the original map distances—specifically, whether the distances might be underestimated or overestimated due to undetected double crossovers or interference.
Step 4: Adjust the original calculations by incorporating corrections for interference or by using more accurate mapping functions (such as the Kosambi or Haldane mapping functions) that account for crossover interference.
Step 5: Revise your answer by explaining how the corrected map distances or recombination frequencies differ from the original ones, and describe the biological implications of these adjustments on the genetic map.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Genetic Mapping and Recombination Frequency

Genetic mapping estimates the relative positions of genes on a chromosome based on recombination frequencies. The frequency of crossover events between genes reflects their physical distance, with closer genes recombining less often. Understanding this helps interpret map distances and their potential inaccuracies.
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Limitations and Inaccuracies in Genetic Maps

Genetic maps can be inaccurate due to factors like interference, multiple crossovers, and limited sample sizes. These factors can cause underestimation or overestimation of distances between genes, leading to revisions in gene order or distance estimates.
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Mapping Overview

Interpreting and Revising Genetic Data

Revising answers based on new data or recognized inaccuracies involves critical analysis of mapping results. This includes reassessing gene order, distances, and considering alternative explanations or additional experiments to improve map accuracy.
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Related Practice
Textbook Question

An organism of the genotype AaBbCc was testcrossed to a triply recessive organism (aabbcc). The genotypes of the progeny are presented in the following table.

If these three genes were all assorting independently, how many genotypic and phenotypic classes would result in the offspring, and in what proportion, assuming simple dominance and recessiveness in each gene pair?

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Textbook Question

An organism of the genotype AaBbCc was testcrossed to a triply recessive organism (aabbcc). The genotypes of the progeny are presented in the following table.

Answer part (a) again, assuming the three genes are so tightly linked on a single chromosome that no crossover gametes were recovered in the sample of offspring.

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Textbook Question

An organism of the genotype AaBbCc was testcrossed to a triply recessive organism (aabbcc). The genotypes of the progeny are presented in the following table.

What can you conclude from the actual data about the location of the three genes in relation to one another?

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Textbook Question

DNA markers have greatly enhanced the mapping of genes in humans. What are DNA markers, and what advantage do they confer?

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Textbook Question

Are mitotic recombinations and sister chromatid exchanges effective in producing genetic variability in an individual? in the offspring of individuals?

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