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46 Cards in this Set
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- Back
- 3rd side (hint)
How does HGT differ from VGT? |
Vertical gene transfer is the transfer of genetic material from parent to offspring |
Horizontal gene transfer is the movement of genetic material between unicellular and/or multicellular organisms |
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What is HGT? |
It is from one independent organism to another |
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What is important in the evolutionary mechanism of many species? |
The ability to pass along genes using HGT |
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What characteristics does stable recombinant have? |
Donor and recipient |
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What are the three mechanisms that have evolved in bacteria to create recombinants? |
Transformation Transduction Conjugation |
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Can bacteria that use HGT, transfer genes to the same or different species? |
Yes, they can transfer to the same or different species |
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What are the fates of horizontally transferred genes? |
1. Population of stable recombinants 2. No stable recombinants |
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What is transformation? |
It is the genetic transfer process by which DNA is incorporated into a recipient cell and brings about genetic change |
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What is competent transformation? |
Competent cells are cells that are capable of taking up (naked/ foreign) DNA and being transformed. |
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What are the (two) transformable bacteria? |
Bacillus and Neisseria |
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What does strains of bacteria that are NOT naturally transformable do to make them competent? |
There are specific procedures that they can undergo to become transformable such as electroporation |
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What is electroporation? |
It is when electricity is used to for cells to take up DNA for transformation |
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What are the steps of natural transformation? |
1. Binding DNA 2. Uptake of single- stranded DNA 3. RecA-mediated homologous recombination |
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During natural transformation what is highly regulated? |
Integration of transforming DNA is highly regulated |
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What is transfection? |
Transformation of bacteria with DNA extracted from bacterial virus. Integration or replication of the bacteriophage |
NOT to be confused with TRANSDUCTION |
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What is transduction? |
The transfer of DNA from one cell to another by a bacteriophage due to mispackaging of the bacteriophage genome |
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What are the two modes of transduction? |
1. Generalised transduction 2. Specialised transduction |
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What is generalised transduction? |
DNA from any portion of the host genome is packed inside the virion |
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What is specialised transduction? |
DNA from specific region of the host chromosome is integrated directly into the virus genome |
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In generalised transduction what are the two characteristics of the virus? |
1. Virus can be temperate or virulent 2. Low efficacy |
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In specialised transduction what are the two characteristics the DNA can show? |
1. DNA of temperate virus excises incorrectly and takes adjacent host genes along with it 2. Transducing efficiency can be high |
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What is phage conversion in transduction? |
Alteration of the phenotype of a host cell by lysogenization |
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What is non-defective temperate phage conversion? |
It is where a phage lysogenizes a cell and becomes a prophage |
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Where are prophages apparent? |
They are apparent in bacterial genomes and are more comment than previously thought |
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What happens to host cells after phage conversion? |
Host cells become immune to further infection by the same phage as they occupy the integration site this is called homoimmunity. Other phenotypical changes can occur |
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What is bacterial conjugation (mating)? |
It is a mechanism of verticle transfer that involves cell to cell contact 1. Plasma encoded mechanism 2. Donor cell 3. Recipient cell |
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What is a donor cell in conjugation? |
A donor cell contains a conjugative plasmid |
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What is a recipient cell in conjugation? |
A recipient cell does not contain a plasmid |
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What are F (fertility) plasmids in conjugation? |
Circular DNA molecules that contain genes that regulate gene replication |
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What are the three things that F plasmids contain? |
1. Genes that regulate DNA replication 2. Contain several transposable elements that allow host chromosome integration 3. Contains tra genes that encode transfer functions |
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What are sex pilus’? |
They are essential for conjugation and are produced only by the donor cell |
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In conjugation how does DNA synthesis occur? |
DNA is synthesised by rolling circle replication which is a mechanism also used by some viruses |
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What type of plasmid is a episome? |
F (fertility) plasmid |
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What is F plasmid able to do because it is an episome? |
It can integrate into the host chromosome |
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What are cells that possess a Nonintegrated F plasmid called? |
F+ |
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What are cells that possess F plasmids called? |
Hfr |
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What does Hfr stand for? |
High frequency of recombination |
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What does Hfr mean? |
It means that it has high rates of genetic recombination between genes on the donor chromosome and those of the recipient |
What does it do? |
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What does the presence of the F plasmid result in? |
It results in alterations in cell properties |
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What are the alteration in the cell properties that are a direct result of F plasmids? |
Ability to synthesise F pilus Mobilisation of DNA for transfer to another cell Alteration of surface receptors so that the cell can no longer act as a recipient in conjugation |
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What do insertion sequences do? |
Facilitate homologous recombination Plasmid is now part of chromosome |
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Where are insertion sequences present? |
F plasmid and E. Coli chromosome |
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Why does the recipient cell not become a Hfr cell? |
Because only a portion if the integrated F plasmid is transferred by the donor |
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What causes genes to transfer in a different order? |
Hfr strains that differ in the integration position of the F plasmid in the chromosome transfer genes in different orders |
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What can genetic crosses with Hfr strains be used for? |
They can be used to map the order of genes on the chromosome |
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What are F’ plasmids? |
Previously integrated F plasmids that have excised and captured some chromosomal genes |
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