Term
| what are the advantages of using bacteria for genetics? |
|
Definition
cheap and easy to grow
short generation time
haploid - easy to see effect of mutations |
|
|
Term
| which bacteria is commonly used? |
|
Definition
| Escherichia coli but not the 0157 strain. this is associated with food poisoining. |
|
|
Term
| if you innoculate a few bacteria on a agar plate what would you get? |
|
Definition
| a colony where each bacteria lands |
|
|
Term
| if you innoculate a million bacteria in an agar plate what would you get? |
|
Definition
| a bacterial lawn due to confluent growth. |
|
|
Term
| what would you see if you put a few bacteria in a media? |
|
Definition
| the media would become increasingly cloudy as the bacteria multiply |
|
|
Term
| what type of DNA has E. coli got? |
|
Definition
| a single double stranded circular chromsome compacted in the nucleoid. |
|
|
Term
| how many base pairs and how many genes in the E.coli? |
|
Definition
base pairs 4.6 million
genes 4500 |
|
|
Term
the nucleiod containing bacterial DNA occupies
a. a small fraction of the cell volume
b. a large fraction of the cell volume? |
|
Definition
| b. a large fraction of the cell volume. |
|
|
Term
|
Definition
| viruses that can infect bacteria. they are structurally and functionally diverse. |
|
|
Term
| name the 2 bacteriophage life cycles |
|
Definition
lytic (virulent) results in host cell lysis
lysogenic (temperate) viral DNA integrated with host. remains dormant and replicates with host dna. |
|
|
Term
| in the lytic cycle how many sets of proteins are needed to assemble the phage? |
|
Definition
3 sets.
head
tail
tail fibres |
|
|
Term
| in the lytic cycle how does the phage escape the host cell? |
|
Definition
| directs lysozyme that digests the bacterial cell wall. damaged cell wall results in osmosis causing cell to swell and burst and phage escapes releasing 100-200 phage particles. |
|
|
Term
| give an example of a temperate phage |
|
Definition
|
|
Term
| what is a bacteria with viral DNA intergrated in its chromsome known as? |
|
Definition
|
|
Term
| what can induce the lambda phage to go from lysonic to lytic cycle? |
|
Definition
|
|
Term
| gene transfer and recombination occurs through 3 processes in bacteria. what are they? |
|
Definition
Transformation
Transduction
Conjugation |
|
|
Term
|
Definition
| taking up naked DNA from environment can be in the form of a plasmid. |
|
|
Term
|
Definition
| transfer of bacterial genes form one bacteria to another by a bacteriophage. |
|
|
Term
| how many types of transduction are there? |
|
Definition
2
generalised - lytic/virulent phage
specialised - temperate/lysogenic phage |
|
|
Term
| explain generalised transduction. |
|
Definition
only in lytic/ virulent phage.
after infecting host, DNA is hydrolised into pieces and phage DNA/proteins are made.
occasionally bacterial dna is packaged in phage capsid.
transducing phages infect new hosts, crossing over takes place and recombinant bacteria result |
|
|
Term
| explain speacialised transduction |
|
Definition
only in Lysogenic/temperate phage.
prophage intergrates dna between 2 genes. occasionaly prophage exits incorrectly taking with it part of the bacterial dna. phage particle carry bacterial dna. crossing over takes place when phage infects new bacteria resulting in recombinant bacteria. |
|
|
Term
| what is conjugation involving the F factor known as? |
|
Definition
| rolling circle replication |
|
|
Term
| what must a bacteria have in order to be able to form sex pili? |
|
Definition
| the F factor (fertility factor -a plasmid) |
|
|
Term
| how does conjugation promote variation? |
|
Definition
| whilst the the F factor is being transferred the dna comes through in a linear fashion and then rolls up. sometime the mating bridge is broken before the whole f factor is transfered resulting in not all of the dna transferred thus a different set. |
|
|
Term
| what is the mating bridge in conjugation also known as? |
|
Definition
|
|
Term
| in conjugation what is the recipient bacterial cell known as? |
|
Definition
|
|
Term
| does the donor keep a copy of the F factor? |
|
Definition
|
|
Term
| how is a F+ male converted into a Hfr male? what is a Hfr male? |
|
Definition
| the F+ is a plasmid. Intergration of it into the chromsome makes it into a Hfr cell. Hfr is High Frequency recombination. |
|
|
Term
| when a Hfr is transferring it dna to a F- bacterium what can happen? |
|
Definition
| not all of the DNA is transferred thus the bits that are transfered can cross over with host dna to make recombinant F- bacterium |
|
|
Term
the cell that has the f factor is aka?
The cell that doesnt have it is aka? |
|
Definition
F+ if they have plasmid
F- if they dont |
|
|
Term
| genes which code for proteins required all the time by the bacteria are? |
|
Definition
|
|
Term
| genes that are only active when required are called? |
|
Definition
|
|
Term
| in bacterial cells when does transcription begin? |
|
Definition
| when RNA Polymerase binds to a promoter |
|
|
Term
| in negative regulation the binding of a repressor does what to transcription? |
|
Definition
|
|
Term
| explain the control of tryptophan biosynthesis |
|
Definition
| when tryptophan is present, it is bound to the repressor as a corepressor, the operon is off because there is no need to make any unessecary protein if it is already available. but when tryptophan is absent it is not bound to the repressor, the repressor is not blocking the operator binding site and mRNA is made to synthesise proteins for tryptophan. |
|
|
Term
| what is polycistronic messaging? |
|
Definition
mRNA that carry several open reading frames each of which is tanslated into a polypeptide. These polypeptides usually have a related function (they often are the subunits composing a final complex protein)
A monocistronic mRNA is when it contains the genetic information to translate only a single protein chain (polypeptide) |
|
|
Term
| what 3 enzymes are produced when the lac operon is on? |
|
Definition
B-galactosidase
Permease
transacetylase |
|
|
Term
| what is the name of the inducer that inactivates the repressor in lac operon? |
|
Definition
|
|
Term
| why is the repressor active when lactose is absent? |
|
Definition
| it doenst have to make enzymes to break down lactose if lactose isnt present. it prefers to use glucose anyways. |
|
|
Term
| binding to promoter to prevent transcription is an example of? |
|
Definition
|
|
Term
| what happens when tyrphonin binds to repressor? |
|
Definition
| it binds to operator and transcripted is prevented |
|
|
Term
| in the absence of lactose lac operon is? |
|
Definition
|
|
Term
| binding of a molecule to the operator to turn on gene expression is an example of ? |
|
Definition
|
|
Term
| what does permease do in lac operon? |
|
Definition
| creates lactose permeable pore in bacteria which make it quicker for lactose to come into the cell |
|
|
Term
| what does B -galactosidase do? |
|
Definition
| break down lactose into galactose and glucose |
|
|
Term
| what are the 3 genes in the lac operon? |
|
Definition
|
|
Term
| how many genes in try operon? |
|
Definition
5
trpE trpD trpC trpB trpA |
|
|
Term
| what role does cAMP play in lac operon? |
|
Definition
| when lactose is present and glucose is scarce there are high levels of cAMP. this binds to its receptor protein called CRP and this binds to the promoter region. result:Abundant lac mRNA synthesis |
|
|
Term
| when glucose is abundant what happens to levels of cAMP? |
|
Definition
| they are low. and this results in little lac mRNA synthesis because prefers using glucose |
|
|
