Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

5. Genetics of Bacteria and Viruses

Transduction

Genetics

5. Genetics of Bacteria and Viruses

Transduction

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1:56 minutes

Problem 9

Textbook Question

How is the frequency of cotransduction related to the relative positions of genes on a bacterial chromosome? Draw a map of three genes and describe the expected relationship of cotransduction frequencies to the map.

Verified step by step guidance

Understand the concept of cotransduction: Cotransduction refers to the simultaneous transfer of two or more genes from a donor bacterium to a recipient bacterium via a bacteriophage. This process occurs when the genes are close enough on the bacterial chromosome to be packaged into the same phage particle during transduction.

Explain the relationship between cotransduction frequency and gene distance: The frequency of cotransduction is inversely proportional to the distance between genes on the bacterial chromosome. Genes that are closer together are more likely to be cotransduced because they are more likely to fit within the same fragment of DNA packaged by the bacteriophage.

Draw a hypothetical gene map: Consider three genes (A, B, and C) on a bacterial chromosome. Assume the relative positions are as follows: A and B are close together, while C is farther away from both A and B. The map could be represented as: A---B----------------C, where the dashes represent relative distances.

Describe the expected cotransduction frequencies: Based on the map, the cotransduction frequency between A and B will be higher because they are closer together. The cotransduction frequency between A and C, as well as between B and C, will be lower because C is farther away from both A and B.

Summarize the relationship: The closer two genes are on the bacterial chromosome, the higher their cotransduction frequency. This relationship can be used to infer the relative positions of genes and construct genetic maps based on experimental cotransduction data.

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Key Concepts

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

Cotransduction

Cotransduction is a genetic phenomenon where two or more genes are transferred together from one bacterium to another via a bacteriophage. The likelihood of cotransduction occurring is influenced by the physical proximity of the genes on the bacterial chromosome. Genes that are closer together are more likely to be packaged into the same viral particle, leading to higher cotransduction frequencies.

Gene Mapping

Gene mapping involves determining the relative positions of genes on a chromosome. In bacteria, this is often done using cotransduction frequencies as a measure of distance between genes. By analyzing how often two genes are cotransduced, researchers can infer their relative locations, with closer genes showing higher cotransduction rates.

Bacterial Chromosome Structure

Bacterial chromosomes are typically circular and contain genes arranged in a linear order. The structure of the chromosome affects gene expression and the likelihood of genetic recombination events, such as cotransduction. Understanding the organization of genes on the chromosome is crucial for predicting the outcomes of genetic experiments and the relationships between gene positions.

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Related Practice

Multiple Choice

True or False:Transduction uses viruses to transfer foreign DNA into bacteria

Specialized transduction differs from generalized transduction because specialized transduction is defined by what?

A cotransduction experiment was performed with two bacteria strains. The first train has the genotype l+ g m+ while the second strain has the genotype of l g+ m. The researchers found that 46 colonies had cotransduced m+ with l+, while only 25 colonies had cotransduced g with l+. Using this information determine which of the following gene pairs are closest together.

How do we know that bacteriophages recombine genetic material through transduction and that cell-to-cell contact is not essential for transduction to occur?

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Textbook Question

A triple-auxotrophic strain of E. coli having the genotype phe⁻ met⁻ ara⁻ is used as a recipient strain in a transduction experiment. The strain is unable to synthesize its own phenylalanine or methionine, and it carries a mutation that leaves it unable to utilize the sugar arabinose for growth. The recipient is crossed to a prototrophic strain with the genotype phe⁺ met⁺ ara⁺. The table below shows the selected marker and gives cotransduction frequencies for the unselected markers.

Use the cotransduction data to determine the order of these genes.

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Textbook Question

A triple-auxotrophic strain of E. coli having the genotype phe⁻ met⁻ ara⁻ is used as a recipient strain in a transduction experiment. The strain is unable to synthesize its own phenylalanine or methionine, and it carries a mutation that leaves it unable to utilize the sugar arabinose for growth. The recipient is crossed to a prototrophic strain with the genotype phe⁺ met⁺ ara⁺. The table below shows the selected marker and gives cotransduction frequencies for the unselected markers.

Identify the compounds present in each of the selective media.

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Textbook Question

The phage P1 is used as a generalized transducing phage in an experiment combining a donor strain of E. coli of genotype leu⁺ phe⁺ ala⁺ and a recipient strain that is leu⁻ phe⁻ ala⁻. In separate experiments, transductants are selected for leu⁺ (Experiment A), for ala⁺ (Experiment B), and for phe⁺ (Experiment C). Following selection, transductant genotypes for the unselected markers are identified. The selection experiment results below show the frequency of each genotype.

In Experiment B, why are there no transductants with the genotype leu⁻ ala⁺?

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Textbook Question

The phage P1 is used as a generalized transducing phage in an experiment combining a donor strain of E. coli of genotype leu⁺ phe⁺ ala⁺ and a recipient strain that is leu⁻ phe⁻ ala⁻. In separate experiments, transductants are selected for leu⁺ (Experiment A), for ala⁺ (Experiment B), and for phe⁺ (Experiment C). Following selection, transductant genotypes for the unselected markers are identified. The selection experiment results below show the frequency of each genotype.

Diagram the crossover events that form each of the transductants in Experiment A.

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