Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages

Klug - Concepts of Genetics 12th Edition

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Klug 12th Edition

Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages

문제 1c

6장, 문제 1c

How do we know whether or not genetic recombination between bacteria involves cell-to-cell contact?

검증된 단계별 안내

Understand the concept of genetic recombination in bacteria, which can occur through different mechanisms such as transformation, transduction, and conjugation. Among these, conjugation specifically requires direct cell-to-cell contact.

Design an experiment where two bacterial strains with distinguishable genetic markers are mixed under conditions that either allow or prevent physical contact between cells. For example, use a filter that permits the passage of DNA but not whole cells.

If recombination occurs only when cells are allowed to physically touch (no filter or a filter that allows cell contact), but not when separated by a barrier that prevents contact, this suggests that recombination requires cell-to-cell contact.

Measure the frequency of recombinant bacteria in both conditions by plating on selective media that only allows growth of recombinants, and compare the results.

Conclude that genetic recombination involves cell-to-cell contact if recombinants are observed only when cells can physically interact, indicating conjugation as the mechanism.

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Genetic Recombination in Bacteria

Genetic recombination in bacteria is the process by which DNA is exchanged between bacterial cells, leading to genetic variation. It can occur through transformation, transduction, or conjugation, each involving different mechanisms and requirements.

Bacterial Conjugation and Cell-to-Cell Contact

Conjugation is a form of genetic recombination that requires direct physical contact between bacterial cells, typically mediated by a pilus. This contact allows the transfer of plasmid or chromosomal DNA from a donor to a recipient cell.

Experimental Methods to Test Cell Contact Requirement

To determine if recombination requires cell-to-cell contact, experiments use physical barriers like filters that allow DNA passage but prevent cell contact. If recombination occurs only when cells can touch, it confirms the necessity of direct contact.

관련 실천

교과서 질문

How do we know that bacteria undergo genetic recombination, allowing the transfer of genes from one organism to another?

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교과서 질문

In this chapter, we have focused on genetic systems present in bacteria and on the viruses that use bacteria as hosts (bacteriophages). In particular, we discussed mechanisms by which bacteria and their phages undergo genetic recombination, which allows geneticists to map bacterial and bacteriophage chromosomes. In the process, we found many opportunities to consider how this information was acquired. From the explanations given in the chapter, what answers would you propose to the following questions? How do we know that intergenic exchange occurs in bacteriophages?

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교과서 질문

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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교과서 질문

How do we know that genes exist in bacteria and bacteriophages?