Questions and Answers
Which of the following are factors that contribute to high genetic diversity in prokaryotes? (Select all that apply)
How does rapid reproduction lead to genetic diversity?
If a mutation in DNA replication occurs in one generation, some of the offspring will be abnormal.
What is the effect of mutation on genetic diversity?
Mutations can quickly increase genetic diversity in species with short generation times and large populations.
What is genetic recombination?
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How does genetic recombination occur in humans?
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Which of the following are mechanisms of genetic recombination in prokaryotes? (Select all that apply)
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What is horizontal gene transfer?
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What is transformation in prokaryotes?
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What role does transduction play in natural bacterial populations?
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What happens during homologous DNA exchange in transformation?
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What is transduction?
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What is the first step in the process of transduction?
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What occurs in step 2 of transduction?
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What happens in step 3 of transduction?
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Explain step 4 of transduction.
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What is conjugation?
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Bacterial DNA transfer is always two-way.
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What initiates E. coli conjugation?
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What is an F factor?
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What is an F plasmid?
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What are F- cells?
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Describe the process of conjugation involving an F plasmid.
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What are Hfr cells?
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What occurs during Hfr cell conjugation?
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What is the process of conjugation involving Hfr cells?
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What is bacterial dysentery?
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What did researchers find out about bacterial resistance?
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What are R plasmids?
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What is a problem associated with R plasmids?
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Study Notes
High Genetic Diversity in Prokaryotes
- High genetic diversity in prokaryotes is facilitated by rapid reproduction, mutation, and genetic recombination, allowing for swift evolutionary changes.
Rapid Reproduction
- Mutations occurring during DNA replication can lead to abnormalities in offspring; spontaneous mutation rate is approximately 1 in 10 million per cell division.
- Bacteria can undergo up to 9 million cell divisions daily in a human host, leading to numerous potential mutations.
Mutation and Genetic Diversity
- Mutations contribute quickly to genetic diversity in species characterized by short generation times and large populations, enhancing reproductive capabilities.
Genetic Recombination
- Genetic recombination increases diversity by combining DNA from two distinct sources, resulting in new genetic variants.
Genetic Recombination in Humans
- In humans, meiosis and fertilization combine DNA from two individuals into a single zygote, creating genetic diversity.
Mechanisms of Genetic Recombination in Prokaryotes
- The three main mechanisms of genetic recombination are transformation, transduction, and conjugation.
Horizontal Gene Transfer
- Horizontal gene transfer allows for gene movement between different species, increasing genetic diversity across prokaryotic populations.
Transformation
- Transformation occurs when a prokaryotic cell incorporates foreign DNA from its surroundings, potentially altering its genotype and phenotype.
- Non-pathogenic cells can acquire pathogenic traits by taking up DNA that includes pathogenicity alleles.
Role of Transduction
- Natural bacterial populations use transduction, where bacteriophages transport DNA between closely related bacterial cells, facilitating genetic diversity.
Homologous DNA Exchange
- This exchange occurs in transformation, replacing one allele with another, contributing to genetic diversity.
Transduction Process
- Bacteriophages can accidentally carry prokaryotic genes from one bacterial host to another during their replication cycle.
Steps of Transduction
- A phage infects a donor bacterial cell, leading to the replication of phage DNA and potential destruction of host DNA, resulting in packaging of bacterial DNA into new phage particles.
Conjugation
- Conjugation involves one-way DNA transfer between prokaryotic cells, typically of the same species, through temporary connections known as sex pili.
E. coli Conjugation
- Initiated by the formation of a sex pilus between two bacteria, allowing for the transfer of DNA through a mating bridge.
F Factor and F Plasmid
- The F factor consists of genes necessary for pili production and can exist as a plasmid within bacterial chromosomes. Cells with the F plasmid are termed F+ cells, functioning as donors during conjugation.
F- Cells
- Cells lacking the F plasmid are F- and act as recipients during conjugation; if an F+ cell transfers its F plasmid, the F- cell can become F+.
Conjugation Process
- Involves the formation of a mating bridge, synthesis of new strands of DNA from broken F plasmids, and completion of DNA transfer, resulting in two F+ cells.
Hfr Cells
- Hfr cells have the F factor integrated into their chromosome, allowing for the transfer of chromosomal genes during conjugation.
Hfr Conjugation Process
- Involves homologous DNA exchange between Hfr and F- cells, resulting in recombination and new genetic traits for the recipient.
Bacterial Dysentery
- Caused by Shigella, leading to severe diarrhea that is typically resistant to antibiotics due to bacterial resistance mechanisms.
Research on Bacterial Resistance
- Resistance may arise from mutations in chromosomal genes or pre-existing resistance genes that encode enzymes hindering antibiotic efficacy.
R Plasmids
- R plasmids contain genes that confer resistance to antibiotics, complicating treatment options and contributing to public health challenges.
Issues with R Plasmids
- R plasmids can encode pili that facilitate conjugation, allowing rapid transfer of resistance traits among bacteria, sometimes bestowing resistance to multiple antibiotics.
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Description
This quiz covers the factors that contribute to high genetic diversity in prokaryotes, emphasizing rapid reproduction, mutation, and genetic recombination. Understanding these concepts is crucial for grasping how prokaryotes evolve quickly to adapt to changing environments.