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Reca Protein

Binds to cells DNA and donor DNA; Exchanges a strand; passes to all descendants.

Transduction

Bacterial DNA is transferred from donor cell to recipient cell inside of a virus infecting bacteria.

-by a bacteriophage

1st step of transduction

Phage infects donor bacterial cell

2nd step of transduction

Phage DNA/proteins are made and bacterial chromosomes are broken into peoces.

3rd step of transduction

Sometimes peices of bacterial dna are stored in phase protein coat. Donor cell lyses; releasing phase particles containing bacterial DNA.

4th step of transduction

Paige carrying bacterial DNA infects a new host cell; recipient cell.

5th step of transduction

Recombination can occur making a recombinant call with a genotype different from both the donor and recipient cell.

Transformation

Horizontal transfer of genes as “naked” DNA.

Conjugation

Horizontal transfer of genes through “cell to cell” contact

Transduction

Horizontal transfer of DNA using bacteriophage

Operator

Acts as a traffic light for transcription of the structural genes.

LAC operon

Inducible operon with 2 short strands of DNA.

Combination of the 3 lac structural genes and adjoining regions.

Lac operon promoter

Segment where RNA polymerase initiates transcription.

Lac operon operator

Acts as traffic light for transcription of structural genes.

Operon

Group of genes that are transcribed together and controlled by 1 promoter.

The set of operator/ promoter sites and the structural genes they control.

Lac operon of E.coli

3 enzymes from lac operon are needed to metabolize lactose.

B-galactosidase and Lac permease

Transport lactose intolerant cell of E.coli

Transacetylase

Adds acetyl group to galactose preventing transport out of the cell of E.coli

Central Dogma

DNA 》mRNA》Protein》Function

Prokaryotes

DNA is replicated in cytoplasm.

Transcription and translation happen at the same time in cytoplasm.

Eukaryotes

DNA is replicated in nucleus

Transcription happens in nucleus

Translation happens in cytoplasm.

Frameshift mutations

DNA based pairs are added or removed

Base substitution mutations

Single DNA pair is altered.

Inducible operon

Genes are normally “off”

A repressor binds to DNA and is turned “on” by environmental induced.

Repressible Operon

Genes are normally “on”

Without a repressor binds to DNA and is tuned “off” by environmental core pressure and repressor.

Genetic variation

Allows species to adapt to environmental changes by natural selection.

Ways bacteria achieve genetic variation

Conjugation

Transformation

Transduction

Conjugation

Mediated by conjugative plasmid.

Direct cell to cell contact.

Donor cells carry plasmid; recipient cell doesnt.

Conjugation

The plasmid is replicated during transfer of a single stranded copy of DNA to the recipient.

A complementary strand is synthesized.

Transformation

Genes are transferred from 1 bacterium to another as “naked” DNA in a solution.

Encapsulated- the virulent strain

Naked DNA

DNA not in a cell.

Recombination

Some bacteria can come into contact with DNA and take up fragments.

They then integrate it into their own chromosomes.

Transformation

Some bacteria can contain DNA that when lysed or die is released into the environment.

I- Gene

Encodes a repressor protein that switches inducible/ repressible operon on and off.

LAC z gene

Codes for B- Galactoseidase that cleaves lactose into simple sugars like glucose when glucose is absent.

LAC y gene

Codes for lactose permease that allow for absorption of lactose by pumping lactose into the cell.

LAC A gene

Encodes for B-Galactoside and transacetylase.

Transfers acteyl group to galactose preventing transport out of the cell.

Promoter

Where RNA polymerase attaches.

Operator

Where LAC repressor binds

Catabolite activator protein (CAP)

Site for protein to bind and be an activator.

E. coli with no lactose

When no lactose is present a LAC repressor protein is bound to operator.

RNA polymerase is now blocked.

No transcription can occur.

E.coli with lactose

When lactose is present so is allolactase.

Allolactase

Acts as an inducer of transcription by binding to the LAC repressor; can no longer bind to operator site. Repressor then leaves operator site.

Lac operon regulation

Depends on the amount of glucose present. Controls intracellular level of CAMP.

LAC operon regulation

When no glucose present- camp accumulates.

Camp binds to allosteric site of CAP

CAP binds to LAC promoter; initiating transcription by helping RNA polymerase bing to promoter.

Transcription of LAC operon

Requires lactose and the absence of glucose.

High glucose- CAMP production is inhibited

Low glucose- trigger CAMP production

High CAMP concentration in LAC operon

More transcription of the LAC operon happens.

Presence of glucose and lactose in LAC operon

Lactose means you still have allolactase that is binding to repressor and inhibiting it from binding to operator.

RNA polymerase can transcribe genes.

LAC operon with no CAMP

No CAMP》 NO CAP to attach to CAP site》 less transcription

TRP operon

Essential for tryptophan production

Repressible operon

Structural genes transcribed and translated; leading to tryptophan synthesis

Excess tryptophan

Acts as a core corepressor binding to repressor protein.

Repressor protein can bind to operator stopping tryptophan synthesis.

Promoter

Where RNA polymerase binds and starts transcription.

Operator

Where the repressor binds

Tryptophan

Can act as a corepressor for repressir when its abundantly present.

The repressor now binds to operator blocking RNA polymerase and stopping translation.

Lac operon

Negative feedback- because transcription is blocked by repressor.

Genes are off untill lactose is present and turns them on.

LAC operon

Positive feedback- CAP binds upstream of operator near promoter and increase transcription.

Genes turn on.

Tryptophan

Turns genes off that are normally on.