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Microbiology - Lecture Thirty Four : Microbial Genetics

Q: What are the properties of bacterial genome ?

Single circular chromosome No nuclear membrane Nucleoid : defined, non-membrane bound region that chromosome occupies within cell Plasmids : smaller, self-replicating, circular DNA found in cytosol (separate to the chromosome)

Q: What are the differences between vertical and horizontal gene transfer ?

VERTICAL : Gene transferred onto the next generation of daughter cells E.g parent --> offspring HORIZONTAL : Genes transferred onto the same generation of cells Recipient cell can be of different species to donor Main mechanism of transferring genes to maintain virulence E.g one organism --> another living organism

Q: Explain the 'Transduction' strategy that generate genetic diversity in bacteria ?

Transfer of DNA via replicating virus (bacteriophage) Occurs as replicating bacteriophage may accidentally incorporate some of the host cell’s DNA into its own viral genome Important tool for horizontal gene transfer in gram +ve bacteria (as their cell capsule is very impenetrable) Donor cell dies, as the the replicating bacteriophage lyse the cell in order to infect other bacterial hosts

Q: Explain the 'Conjugation' strategy that generate genetic diversity in bacteria ?

Donor cell stays alive Requires cell-cell contact 1 single stranded DNA from the donor plasmid is transferred via a sex pili (thin, fibrous protein tube) to the recipient cell The recipient cell then replicates the donor DNA strand : double stranded donor DNA plasmid Often a process used to transfer antibiotic resistant genes

6 important questions on Microbiology - Lecture Thirty Four : Microbial Genetics

What are the properties of bacterial genome ?

Single circular chromosome
No nuclear membrane
Nucleoid : defined, non-membrane bound region that chromosome occupies within cell
Plasmids : smaller, self-replicating, circular DNA found in cytosol (separate to the chromosome)

What are the differences between vertical and horizontal gene transfer ?

VERTICAL :

Gene transferred onto the next generation of daughter cells
E.g parent --> offspring

HORIZONTAL :

Genes transferred onto the same generation of cells
Recipient cell can be of different species to donor
Main mechanism of transferring genes to maintain virulence
E.g one organism --> another living organism

What are the 4 strategies that generate genetic diversity in bacteria ?

Bacteria have incredible genetic diversity, due to the following things:

Mutations
Transformation
Transduction
Conjugation

These factors, along with their shorter lifespans and shorter replication cycles (binary fissions), allows genetic variation to occur much quicker

Explain the "Transformation" strategy that generate diversity in bacteria ?

Occurs when recipient cell takes up DNA fragments from the environment or surroundings
This DNA is from nearby dead organisms)
Competency = cell’s ability to take up DNA from their environment

Explain the "Transduction" strategy that generate genetic diversity in bacteria ?

Transfer of DNA via replicating virus (bacteriophage)
Occurs as replicating bacteriophage may accidentally incorporate some of the host cell’s DNA into its own viral genome
Important tool for horizontal gene transfer in gram +ve bacteria (as their cell capsule is very impenetrable)
Donor cell dies, as the the replicating bacteriophage lyse the cell in order to infect other bacterial hosts

Explain the "Conjugation" strategy that generate genetic diversity in bacteria ?

Donor cell stays alive
Requires cell-cell contact
1 single stranded DNA from the donor plasmid is transferred via a sex pili (thin, fibrous protein tube) to the recipient cell
The recipient cell then replicates the donor DNA strand : double stranded donor DNA plasmid
Often a process used to transfer antibiotic resistant genes