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Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 6 - Genetic Analysis and Mapping in Bacteria and BacteriophagesProblem 26
Chapter 6, Problem 26

In a cotransformation experiment, using various combinations of genes two at a time, the following data were produced. Determine which genes are 'linked' to which others.
Table showing successful cotransformations: a and d, b and c, b and f; unsuccessful pairs include a and b, a and c, a and f, d and b, d and c, d and f, a and e, b and e, c and e, d and e, f and e.

Verified step by step guidance
1
Start by understanding the concept of cotransformation: Cotransformation occurs when two genes are close enough on the same DNA molecule that they are transferred together during transformation. Genes that are cotransformed more frequently are likely to be closer together (linked).
Organize the data into two groups: 'Successful Cotransformation' and 'Unsuccessful Cotransformation'. This will help you identify which gene pairs are likely linked (successful cotransformation) and which are not (unsuccessful cotransformation).
Analyze the 'Successful Cotransformation' data. For each pair of genes listed, note that these genes are likely linked because they are frequently cotransformed together. For example, 'a and d' are likely linked because they appear in the successful cotransformation group.
Analyze the 'Unsuccessful Cotransformation' data. For each pair of genes listed, note that these genes are likely not linked because they are not frequently cotransformed together. For example, 'd and b' are likely not linked because they appear in the unsuccessful cotransformation group.
Construct a linkage map or grouping based on the successful cotransformation data. Group genes that are frequently cotransformed together into clusters, and separate clusters based on the unsuccessful cotransformation data. This will help you determine which genes are linked to which others.

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Key Concepts

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

Cotransformation

Cotransformation refers to the simultaneous transfer of two or more genes into a recipient organism, often observed in bacterial transformation experiments. In this context, successful cotransformation indicates that the genes are physically close on the chromosome, allowing them to be inherited together. This concept is crucial for understanding gene linkage and the genetic mapping of organisms.

Gene Linkage

Gene linkage occurs when genes are located close to each other on the same chromosome, leading to their co-inheritance during meiosis. Linked genes do not assort independently, which can be determined through experiments like cotransformation. Understanding gene linkage is essential for interpreting the results of the experiment and determining which genes are associated with one another.
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Chi Square and Linkage

Genetic Mapping

Genetic mapping is the process of determining the relative positions of genes on a chromosome based on their recombination frequencies. In the context of cotransformation data, successful combinations suggest proximity on the chromosome, while unsuccessful combinations indicate greater distances. This mapping is vital for understanding the genetic architecture of organisms and predicting inheritance patterns.
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Mapping Overview
Related Practice
Textbook Question

An Hfr strain is used to map three genes in an interrupted mating experiment. The cross is Hfr/a⁺b⁺c⁺ rif x F⁻/a⁻b⁻c⁻ rifT (No map order is implied in the listing of the alleles; rifT is resistance to the antibiotic rifampicin.) The a⁺ gene is required for the biosynthesis of nutrient A, the b⁺ gene for nutrient B, and the c⁺ gene for nutrient C. The minus alleles are auxotrophs for these nutrients. The cross is initiated at time = 0, and at various times, the mating mixture is plated on three types of medium. Each plate contains minimal medium (MM) plus rifampicin plus specific supplements that are indicated in the following table. (The results for each time interval are shown as the number of colonies growing on each plate.)

Based on these data, determine the approximate location on the chromosome of the a, b, and c genes relative to one another and to the F factor.

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Textbook Question

An Hfr strain is used to map three genes in an interrupted mating experiment. The cross is Hfr/a⁺b⁺c⁺ rif x F⁻/a⁻b⁻c⁻ rifT (No map order is implied in the listing of the alleles; rifT is resistance to the antibiotic rifampicin.) The a⁺ gene is required for the biosynthesis of nutrient A, the b⁺ gene for nutrient B, and the c⁺ gene for nutrient C. The minus alleles are auxotrophs for these nutrients. The cross is initiated at time = 0, and at various times, the mating mixture is plated on three types of medium. Each plate contains minimal medium (MM) plus rifampicin plus specific supplements that are indicated in the following table. (The results for each time interval are shown as the number of colonies growing on each plate.)

Can the location of the rif gene be determined in this experiment? If not, design an experiment to determine the location of rif relative to the F factor and to gene b.

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Textbook Question

A plaque assay is performed beginning with 1 mL of a solution containing bacteriophages. This solution is serially diluted three times by combining 0.1 mL of each sequential dilution with 9.9 mL of liquid medium. Then 0.1 mL of the final dilution is plated in the plaque assay and yields 17 plaques. What is the initial density of bacteriophages in the original 1 mL?

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Textbook Question

For the experiment in Problem 26, another gene, g, was studied. It demonstrated positive cotransformation when tested with gene f. Predict the results of testing gene g with genes a, b, c, d, and e.

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Textbook Question

Bacterial conjugation, mediated mainly by conjugative plasmids such as F, represents a potential health threat through the sharing of genes for pathogenicity or antibiotic resistance. Given that more than 400 different species of bacteria coinhabit a healthy human gut and more than 200 coinhabit human skin, Francisco Dionisio [(2002) Genetics 162:1525 1532] investigated the ability of plasmids to undergo between-species conjugal transfer. The following data are presented for various species of the enterobacterial genus Escherichia. The data are presented as 'log base 10' values; for example, -2.0 would be equivalent to 10⁻² as a rate of transfer. Assume that all differences between values presented are statistically significant.

What general conclusion(s) can be drawn from these data?

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Textbook Question

Bacterial conjugation, mediated mainly by conjugative plasmids such as F, represents a potential health threat through the sharing of genes for pathogenicity or antibiotic resistance. Given that more than 400 different species of bacteria coinhabit a healthy human gut and more than 200 coinhabit human skin, Francisco Dionisio [(2002) Genetics 162:1525 1532] investigated the ability of plasmids to undergo between-species conjugal transfer. The following data are presented for various species of the enterobacterial genus Escherichia. The data are presented as 'log base 10' values; for example, -2.0 would be equivalent to 10⁻² as a rate of transfer. Assume that all differences between values presented are statistically significant.

In what species is within-species transfer most likely? In what species pair is between-species transfer most likely?

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