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

Bacterial Conjugation

Genetics

5. Genetics of Bacteria and Viruses

Bacterial Conjugation

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1:14 minutes

Problem 3c

Textbook Question

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: What is the genetic basis for a bacterium's being F⁺.

Verified step by step guidance

Understand that the F⁺ bacterium contains a fertility factor (F factor), which is a plasmid—a small, circular piece of DNA that is separate from the bacterial chromosome.

Recognize that the F factor carries genes necessary for the formation of a pilus, a structure that facilitates the transfer of genetic material between bacteria during conjugation.

Note that the F factor also contains an origin of transfer (oriT), which is the specific site where the transfer of the plasmid begins during conjugation.

Realize that the presence of the F factor in a bacterium makes it F⁺, as it has the ability to initiate conjugation and transfer the F factor to an F⁻ bacterium.

Understand that an F⁻ bacterium lacks the F factor and cannot initiate conjugation, but it can receive the F factor from an F⁺ bacterium, thereby becoming F⁺ itself after the transfer.

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Key Concepts

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

F Plasmid

The F plasmid, or fertility plasmid, is a circular piece of DNA found in some bacteria that carries genes necessary for the formation of sex pili and the process of conjugation. Bacteria containing the F plasmid are termed F⁺, allowing them to transfer genetic material to F⁻ bacteria through direct contact. This plasmid plays a crucial role in horizontal gene transfer, contributing to genetic diversity among bacterial populations.

Conjugation

Conjugation is a form of horizontal gene transfer in bacteria where genetic material is transferred from one bacterium to another through direct contact. This process typically involves the formation of a pilus by the F⁺ bacterium, which connects to the F⁻ bacterium, allowing the transfer of the F plasmid. Conjugation is significant for the spread of antibiotic resistance and other traits among bacterial communities.

Hfr Strains

Hfr (high frequency of recombination) strains are bacteria in which the F plasmid has integrated into the bacterial chromosome. This integration allows for the transfer of chromosomal genes during conjugation, leading to genetic recombination. Hfr strains are important for studying gene mapping and understanding the mechanisms of genetic exchange in bacteria, as they can transfer large segments of genetic material to F⁻ recipients.

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Related Practice

Textbook Question

For bacteria that are F⁺, Hfr, F', and F⁻ perform or answer the following.

Describe the state of the F factor.

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Textbook Question

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

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Textbook Question

The flow diagram identifies relationships between bacterial strains in various F factor states. For each of the four arrows in the diagram, provide a description of the events involved in the transition.

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Textbook Question

Conjugation between an Hfr cell and an F⁻ cell does not usually result in conversion of exconjugants to the donor state. Occasionally, however, the result of this conjugation is two Hfr cells. Explain how this occurs.

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Textbook Question

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that chromosome transfer was unidirectional?

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Textbook Question

With respect to F⁺ and F⁻ bacterial matings, answer the following questions: How was it established that physical contact between cells was necessary?

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Textbook Question

List all major differences between:

(a) The F⁺ x F⁻ and the Hfr x F⁻ bacterial crosses

(b) The F⁺, F⁻, Hfr, and F' bacteria.

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Textbook Question

Explain the importance of the following features in conjugating donor bacteria:

pilin protein

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