genetics of bacteria Flashcards
3 phases of bacterial growth
- lag phase - bacteria adapts to medium
- exponential (log) phase - rapid growth
- stationary phase - cells stop diving due to limited nutrients
bacteria - haploid - 1 copy of each gene so if mutation arises, what happens
they are affected as they don’t have another copy of the same gene
….. is the best understood bacterial species, 1st example of a model genetic organism
E.coli
3 ways of genetic exchange in bacteria:
1. conjugation:
transfer of plasmids between bacterial cells
3 ways of genetic exchange in bacteria:
2. transduction:
bacteriophage can package a DNA fragment from the bacterial genome and transfer to another bacterial cell
3 ways of genetic exchange in bacteria:
3. transformation:
bacteria take up DNA from environment
genetic exchange in bacteria
transformation:
- recipient cell takes up donor DNA
- recombination between donor DNA and recipient DNA
- get genetically transformed cell
more DNA you add, more likely to be transformed with bacterial DNA
what is competency of bacteria
few bacteria are capable of taking up DNA by transformation at one time - competency varies depending on state of growth
to enhance competency in a population of E. coli - (3)
-grown in rich liquid culture
-harvested in exponential growth phase
-treated with CaCl2
what is generalised transduction by bacteriophages
when virus (T4) picks up piece of host genomic DNA and transports it to another cell
conjugation - donor cell transfers some genetic info to recipient cell. genetic info is transferred through -
hollow tube of proteins - conjugation pilus
1st plasmid to be discovered
fertility plasmid, carries genes which allow genetic exchange
-30 transfer genes
-origin of replication
-origin of transfer
-3 insertion sequences
R plasmid - bacteria carry genes that have
antibiotic resistance
size of R plasmid
large
size of R plasmid
large
does R plasmid have tra gene
yes
CoIEI plasmid is in
E. coli
size of CoIEI plasmid
small
does CoIEI have tra gene
no
which step of the lytic lifecycle of phage T4 occurs between arrest of host gene expression and induction of DNA replication
enzyme synthesis
