Bacteriology 3: Bacterial Genetics Flashcards
Define gene:
Define genome:
-Section of dna that codes for a protein the fundamental unit of heredity
-total content of the organisms genetic information
Transcription and its steps (5)
Specific genes are copied into smaller (messenger) mRNA
1. RNA polymerase binds to the promoter, DNA unwinds
2. RNA is synthesized by adding base pairs to the Nt bases on the template strand off DNA
3. DNA that has been transcribed rewinds
4. Transcription reaches the terminator
5. Complete RNA strand… (RNA poly is released, and DNA helix re-forms)
Translation and it’s steps
Using mRNA as the template. The ribosomes create the sequence of amino acids.
1. Entrance of tRNA
2. Formation of peptide bond
-the growing chain at A site
3. Discharge of tRNA at E site
4. First translocation
When does bacteria do transcription and translation?
Can happen together
As soon as a bacterial RNA polymerase starts transcribing DNA into mRNA, ribosomes can attach to the growing mRNA strand and begin translating the mRNA into a protein.
Cistron
-define
-polycistronic
-monocistronic
DNA encoding a single protein or polypeptide (often synonymous with “gene”)= It represents the functional unit of genetic information that codes for a protein
-poly: prokaryotes
1 promoter directs synthesis of 1 mRNA that can be translated to more than one polypeptide
In prokaryotes (like bacteria), a single mRNA molecule can carry information for multiple cistrons, producing more than one protein from a single transcript. This is called polycistronic mRNA.
-mono: eukaryotes (we have alternative splicing)
1 promoter directs synthesis of 1 mRNA that usually translates to only 1 protein (Hg)
In eukaryotes (like humans), each mRNA typically corresponds to one cistron, meaning that each mRNA codes for a single polypeptide. This is referred to as monocistronic mRNA.
What is an operon and its components?
Multiple genes transcribed from a single promoter encoding multiple functionally related proteins
-produces a single polycistronic mRNA
An operon is a cluster of genes regulated together by a single promoter and operator in prokaryotes.
components
-Has a promoter = A DNA sequence where RNA polymerase binds to initiate transcription.
-the 3 genes = These are the actual genes that encode for proteins. In an operon, several structural genes are typically transcribed together into a single mRNA molecule (polycistronic mRNA).
-the terminator = A sequence that signals the end of transcription
-Commander
Advantages of genetic transfer
-acquire antibiotic resistance genes
-acquire virulence genes (toxins)
-acquire other advantageous trait genes
Plasmids
-self replication dsDNA that may integrate into the genome but can remain extrachromosomal
-Not essential for survival of bacteria, but can provide survival traits
“Not always circular”
Transposons
-what are they?
-how can they replicate?
Jumping genes
mobile dsDNA can transpose themselves from one location to another within the genome.
-carry genes for self-mobilization
-cannot replicate independently (must be in a genome or plasmid). Transposons moving onto plasmids can be transferred to another cell.
What are the 3 Mechanisms for genetic transfer
Conjugation
Transformation
Transduction
Conjugation
requires direct contact b/w the donor and recipient cell
SEX PILUS
-the donor must contain the F plasmid (fertility) (F+ CELL) = usually the one with more Pili. Has the information and will transfer to recipient cell via a sex pilus
F+ = DONOR!!!!!
once conjugation occurs, the recipient may now perform the same function as the donor since it now contains the F plasmid
What difference does it make if bacteria keep sharing a plasmid that makes a pilus?
ADHERE BETTER (photo shows a gastric bacteria)
Transformation
Free DNA into cell (competence)
Transformation is a process by which bacteria take up free DNA from their environment and incorporate it into their own genome.
Once the extracellular DNA is in the bacteria it may be degraded or integrated through homologous recombination
Indirect transfer (no direct contact, but close proximity is required)
*When bacterial cells die, they often lyse (burst), releasing their DNA into the surrounding environment. This free DNA can be from the same species or different species. Only certain bacteria, known as competent bacteria, are capable of taking up free DNA.
Transduction
-mechanism
-generalized
-during what cycle
Transduction is a process of genetic transfer in bacteria mediated by bacteriophages (viruses that infect bacteria). It involves the transfer of bacterial DNA from one bacterium to another via a bacteriophage.
**
generalized
-bacteriophages (only Viral DNA)
-transducing particles
-replicated to make only bacteriophages
-only making viral DNA
-if the F plasmid is extrachromosomal then
Only the F plasmid is transferred
When the F plasmid is extrachromosomal, it remains separate from the bacterial chromosome, allowing it to replicate independently and be transferred between bacteria via conjugation. This process contributes to the rapid spread of traits like antibiotic resistance within bacterial populations, promoting genetic diversity and adaptability.
The extrachromosomal plasmid is transferred by a sex pilus. Only a single strand transferred. The new cell becomes F+ cell
