Transformation, transduction, and conjugation.
They help regulate gene expression through operons.
Regulating the metabolism of lactose in prokaryotes.
Regulating the synthesis of tryptophan in prokaryotes.
They allow coordinated regulation of genes with related functions.
A unicellular organism that lacks membrane-bound organelles.
Two domains: Archaea and Bacteria.
From 0.5Mb to 10Mb.
Prokaryotic genomes are smaller in size compared to eukaryotic genomes.
Inducible and repressible systems.
DNA/RNA, single-/double-stranded, number of nucleotides, packing of DNA, linearity/circularity, and presence/absence of introns.
Binary fission.
A form of gene transfer where only a few specific genes can be transferred to the recipient cell.
The inserted viral DNA that becomes part of the bacterial chromosome during the lysogenic phase.
Cell growth occurs as the cell elongates.
DNA attaches to the cell membrane at a point called mesosome.
The viral DNA becomes incorporated into the bacterial chromosome at a specific point, forming a prophage.
A cluster of structural genes, a promoter, and an operator.
Ampicillin, tetracycline, and kanamycin.
Negative control.
F. Jacob and J. Monod.
Into operons, where several genes are lined up side by side under the control of a single promoter.
The biosynthesis of tryptophan, an important amino acid.
lacZ, lacY, and lacA.
No, they are often beneficial under stressful conditions.
The lac operon is switched on, but the expression is low (basal) as RNA polymerase does not bind efficiently to the promoter.
Glucose.
The cell membrane folds inwards between the DNA molecules to form a double layer across the long axis of the cell.
Bacterial cells that can take up foreign DNA.
An inducible operon.
Because binary fission is an asexual process.
By mixing two mutant strains of E. coli that cannot synthesize different essential amino acids, resulting in growth of colonies.
Inducible operons and Repressible operons.
New mutations.
Negative control, as the repressor binding blocks transcription.
The repressor protein is inactive and not bound to the operator region, allowing transcription.
The amino acid tryptophan by expressing the five structural genes involved in its biosynthesis.
They enable bacteria to synthesize only the enzymes that are required.
The viral DNA excises itself from the bacterial chromosome, sometimes taking adjacent bacterial DNA with it.
Biosynthesis is stopped as all 5 enzymes involved are not produced.
Due to plasmids conferring antibiotic resistance on bacteria.
Glucose repression.
The transfer of genetic material from one bacterium to another that is not its offspring, leading to genetic recombination.
It refers to the down regulation of enzyme synthesis by the presence of the end product.
It prevents transcription by blocking RNA polymerase from accessing the structural genes.
Negative control by the lac repressor and positive control by cAMP-CAP.
The injected DNA may replace homologous regions of the second cell’s chromosome, leading to genetic recombination.
It codes for lactose permease, which transports lactose into the bacterial cell.
Because any segment of the bacterial DNA may get transferred, not just specific genes.
It acts as an activator when glucose levels are low.
The operon is partially activated but primarily repressed due to glucose.
The active lac repressor molecule.
At the transcriptional level.
It can switch off genes that encode enzymes involved in its synthesis, exemplified by the trp operon.
Lambda phage.
The trp operon.
A cluster of structural genes coding for enzymes involved in the metabolism of lactose in E. coli.
At the origin (Ori C) attached to the cell membrane, near the midpoint of the cell.
It allows lactose to enter the cells, initiating the process of transcription.
cAMP activates the catabolite activator protein (CAP), which enhances transcription of the lac operon.
Positive control, as it increases the expression of genes in the lac operon.
At the termination sequence situated opposite the origin of replication.
Inducible enzymes, produced only in response to the presence of allolactose.
It cannot bind to the operator, allowing RNA polymerase to transcribe the structural genes.
Media that contain the minimum nutrients necessary for growth, generally lacking essential amino acids.
By identifying which essential amino acids need to be added to minimal media for growth.
An area of about 1 μm².
Small, double-stranded, circular, extra-chromosomal DNA.
They allow for co-ordinated regulation of genes involved in a metabolic pathway.
They enable bacteria to utilize various sugars or substrates present in the environment.
It activates the repressor, allowing the repressor-tryptophan complex to bind to the operator and block transcription.
It passes the bacterial DNA along with its own DNA into the new host cell.
Two identical daughter cells.
Because the DNA transferred is usually the same set of genes located near the prophage on the bacterial chromosome.
cAMP level increases, binds to CAP, and enhances RNA polymerase binding to the lac promoter.
Generalised transduction and specialised transduction.
ori C.
Catabolite repression.
DNA gyrase.
The mouse dies, and its tissue contains living bacteria with smooth coats like IIIS.
From 1 kb to 300 kb.
Asexually via binary fission.
Polycistronic mRNA, which contains genetic information for multiple polypeptides.
Eukaryotic mRNA is monocistronic, coding for only one polypeptide.
It binds to the CAP binding site at the lac promoter, enhancing RNA polymerase binding and increasing gene expression.
It acts as a molecular switch to control the access of RNA polymerase to the genes.
β-galactosidase.
A loop consisting of about 100,000 base pairs.
A central protein scaffold attached to the cell membrane.
The non-virulent cell takes up foreign DNA containing the allele for virulence.
Genetic recombination.
In the nucleoid region of the cell.
It serves as a template for synthesizing a complementary strand, forming a double stranded structure.
It acts as a co-repressor to turn off transcription.
Glucose must be absent for maximal expression of the lac operon.
It is 'leaky', meaning a small amount of enzymes for lactose metabolism is still synthesized.
Glucose is a monosaccharide that can be used directly for respiration, while lactose must be hydrolyzed first.
It uses the host’s protein synthesising mechanisms to synthesize its own proteins and DNA.
It demonstrated that bacteria can take up DNA from the environment.
β-galactosidase, which breaks down lactose into glucose and galactose.
Galactoside transacetylase, an enzyme needed in lactose metabolism.
It controls the transcription of all three structural genes.
Acts as a molecular switch, turning on and off the transcription of genes.
A group of genes that code for proteins/enzymes involved in a single metabolic pathway, controlled by a single promoter.
The promoter and the operator.
It prevents wastage of energy and resources.
Plasmids that typically have genes coding for antibiotic resistance.
The transfer of bacterial DNA from one cell to another by means of a bacteriophage.
The transfer of genes from mother to daughter cells during cell division, often involving mutations in parental DNA.
Repressible enzymes.
The cell is divided into two smaller, identical cells.
No, genes are not interrupted by introns.
Structural genes code for proteins, while regulatory genes control the expression of structural genes.
CAP binds to DNA and increases the rate of transcription of the lac operon.
It refers to the repression of lac operon expression in the presence of glucose, allowing bacteria to preferentially use glucose.
A repressor protein which is inactive.
It adds more diversity to a population beyond what mutations provide.
Enzymes cut, twirl, and reseal the double helix.
Discontinuously in the direction back towards the origin at each replication fork.
The genotype and phenotype are altered by the uptake of foreign DNA.
The genes in the operon are switched off by the active form of the repressor protein.
Plasmids that carry genes coding for enzymes that confer resistance to antibiotics.
Each circular DNA strand, still attached to the cell membrane, separates as the cell elongates.
The uptake of a foreign DNA molecule by a bacterial cell from the surrounding environment.
J. Monod and colleagues in 1953.
In a semi-conservative manner, bidirectionally.
Transformation, transduction, and conjugation.
The repressor undergoes a conformational change, preventing it from binding to the operator, allowing RNA polymerase to transcribe the genes.
A promoter, an operator, and five structural genes (trp E, trp D, trp C, trp B, and trp A).
A transforming factor from the S strain converted the non-virulent R strain into the virulent S strain.
The process of making bacterial cells competent using calcium ions and heat shock or electric shock.
It prevents the mouse’s immune system from inhibiting the proliferation of the bacteria.
Introducing DNA fragments containing specific genes, such as the insulin gene, into bacterial cells.
It can result in the expression of genes that encode enzymes involved in breaking it down, exemplified by the lac operon.
The lac operon.
Because even in the presence of high lactose concentration, the synthesis of the 3 enzymes is low.
E. coli will utilize glucose first before starting to utilize lactose.
Any gene from the bacterial host cell can be transferred to the recipient cell.
Via genetic recombination.
cAMP levels are low because glucose transport inhibits adenyl cyclase.
Spontaneous mutations such as insertions, deletions, and base-pair substitutions.
That genetic recombination has occurred, as cells acquired missing genes from the other strain.
It shows the sequential utilization of glucose followed by lactose in a medium containing both.
DNA.
The specific supercoiling of a region can affect the ability of the cell to express genes in that region.
430 μm.
The non-staining region in the interior of the cytoplasm of the bacterial cell.
They can undergo DNA replication independently of chromosomal DNA.
Because the repressor protein is bound to the operator.
The active repressor binds to the operator, blocking RNA polymerase and preventing transcription of structural genes.
It is a repressible system of gene regulation.
It is where RNA polymerase binds to initiate transcription.
Allolactose is an isomer of lactose that acts as an inducer by binding to the repressor, preventing it from blocking transcription.
It can inhibit the first enzyme in the biosynthesis pathway and block transcription of the genes for these enzymes.
By the binding of a specific molecule that changes its shape.
The operon is activated.
A bacterial chromosome and plasmids.
It is made up of a single circular DNA molecule associated with non-histone proteins.
The response of the operon to specific regulatory proteins, such as repressor and activator proteins.
By using the presence of specific nutrients to quickly adjust gene expression.
In the absence of glucose and presence of lactose.
Virulent IIIS strain and non-virulent IIR rough strain.
About 50 loops.
The operon is repressed.
The presence of the F plasmid, which contains the F factor.
The control of whether a gene is expressed and the level of its expression.
To avoid wasting resources and energy on synthesizing proteins/enzymes that are not required.
It allows them to respond rapidly to changes in the environment.
Lactose and glucose concentrations in the environment.
Fragments of the host’s degraded DNA or an entire plasmid can be packaged into new phage particles.
The direct transfer of DNA between two bacterial cells that are in contact.
They are usually turned off but can be induced to turn on in response to a specific molecule.
The lac operon, which is induced in the presence of lactose.
They are usually turned on but can be turned off in response to a specific molecule.
The trp operon, which is repressed in the presence of tryptophan.
Double-stranded 'naked' DNA not associated with histones.
About 5 million base pairs.
The metabolism of lactose.
At the same time and in the same way as the bacterial chromosome.
They are signals that help turn genes on or off in response to environmental cues.
Yes, an operon like the lac operon can be under both types of control.
A virulent smooth strain (S) and a non-virulent rough strain (R).
The transcription and translation of a gene into a functional product.
F+ strain (donor) and F- strain (recipient).
A special piece of DNA that determines the ability to serve as a donor, consisting of about 25 genes.
They act like a grappling hook to draw two bacteria together for DNA transfer.
1. Live non-virulent rough strain (R) - mouse lives; 2. Live virulent smooth strain (S) - mouse dies; 3. Heat-killed virulent smooth strain (S) - mouse lives; 4. Live non-virulent rough strain (R) and heat-killed virulent smooth strain (S) - mouse dies.
When bound to the operator, it prevents RNA polymerase from binding, thus blocking transcription.
The single stranded DNA that is exported to the recipient during conjugation.
They can transfer their genes to other bacteria by conjugation, similar to F plasmids.
It is nicked at the origin of transfer, resulting in the separation of one DNA strand (TDNA) for transfer.
The genes are expressed only when an active form of an activator is present.
