Genetic Diversity in Prokaryotes

Questions and Answers

Which of the following are factors that contribute to high genetic diversity in prokaryotes? (Select all that apply)

Cell differentiation

Mutation (correct)

Rapid reproduction (correct)

Genetic recombination (correct)

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?

The combining of DNA from two sources. Signup and view all the answers

How does genetic recombination occur in humans?

Through meiosis and fertilization. Signup and view all the answers

Which of the following are mechanisms of genetic recombination in prokaryotes? (Select all that apply)

Transformation Signup and view all the answers

What is horizontal gene transfer?

The movement of genes from one species to another. Signup and view all the answers

What is transformation in prokaryotes?

The genotype and phenotype of a prokaryotic cell are altered by the uptake of foreign DNA from its surroundings. Signup and view all the answers

What role does transduction play in natural bacterial populations?

Bacteria have cell surface proteins that recognize DNA from closely related species and transport it into the cell. Signup and view all the answers

What happens during homologous DNA exchange in transformation?

One allele for a gene is replaced with another allele for that gene. Signup and view all the answers

What is transduction?

Phages carry prokaryotic genes from one host cell to another. Signup and view all the answers

What is the first step in the process of transduction?

A phage infects a bacterial cell that carries the A+ and B+ alleles on its chromosome. Signup and view all the answers

What occurs in step 2 of transduction?

The phage DNA is replicated and the cell makes copies of the protein encoded by its genes. Signup and view all the answers

What happens in step 3 of transduction?

A fragment of bacterial DNA carrying the A+ allele is packaged in a phage cell capsid. Signup and view all the answers

Explain step 4 of transduction.

The phage carrying the A+ allele from the donor cell recombines with the recipient DNA, potentially swapping an A- for the A+. Signup and view all the answers

What is conjugation?

DNA transfer between two prokaryotic cells that are temporarily joined by a sex pilus. Signup and view all the answers

Bacterial DNA transfer is always two-way.

False Signup and view all the answers

What initiates E. coli conjugation?

The formation of a sex pilus between two cells. Signup and view all the answers

What is an F factor?

A piece of DNA that consists of 25 genes required for the production of pili. Signup and view all the answers

What is an F plasmid?

The F factor in its plasmid form. Signup and view all the answers

What are F- cells?

Cells without the F plasmid that will function as DNA receivers. Signup and view all the answers

Describe the process of conjugation involving an F plasmid.

An F+ cell forms a mating bridge with an F- cell, and one strand of plasmid DNA breaks and enters the F- cell. Signup and view all the answers

What are Hfr cells?

Donor cells in which the F factor is integrated into the chromosome. Signup and view all the answers

What occurs during Hfr cell conjugation?

Homologous DNA segments are exchanged between Hfr and F- chromosomes. Signup and view all the answers

What is the process of conjugation involving Hfr cells?

An Hfr cell forms a mating bridge with an F- cell and transfers DNA. Signup and view all the answers

What is bacterial dysentery?

A condition that produces severe diarrhea that does not respond to antibiotics. Signup and view all the answers

What did researchers find out about bacterial resistance?

Mutations in chromosomal genes or pathogens can confer resistance to antibiotics. Signup and view all the answers

What are R plasmids?

Resistance plasmids that inhibit the effectiveness of certain antibiotics. Signup and view all the answers

What is a problem associated with R plasmids?

Many R plasmids contain genes that encode pili, enabling DNA transfer by conjugation. Signup and view all the answers

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.