Bacterial Genetics Quiz

The study of how genes function in bacteria and other microorganisms.

E. Coli K12 is a safe and simplified version of E. Coli, lacking toxins, adhesion factors, iron-transport systems, a capsule, plasmids, and having a smaller genome and a rough colony type. This makes it easier to study bacterial genetics.

Replicons are the genetic elements that replicate independently, including the bacterial chromosome and plasmids.

Plasmids are small, extrachromosomal DNA molecules that can carry genes for functions like antibiotic resistance. Their copy number within a cell is closely controlled by genes on the plasmid itself.

Housekeeping genes are essential genes for basic cellular functions like DNA replication, transcription, and translation. They are typically not found on plasmids.

Plasmids that have similar replication control mechanisms cannot coexist stably in the same cell. One plasmid will always outcompete the other.

The original strain of a species, typically found in nature, and often used as a reference for comparison when studying mutants.

A strain carrying a genetic change (mutation) that alters its function or characteristics compared to the wild type.

A change in the DNA sequence of a gene that can disrupt or alter its function.

A variation or alternative form of a gene that can be inherited.

A mutant strain that cannot synthesize a specific essential compound (like an amino acid) and requires it to be supplied in the growth medium.

A strain that can synthesize all the essential compounds it needs to grow and doesn't require any external supplements.

The genetic makeup of an organism, specifically the alleles it carries. It describes the differences from the wild type.

The observable characteristics or traits of an organism, resulting from its genotype and interaction with the environment.

A method to isolate cells with a specific genotype based on their ability to grow under specific conditions, often by providing or removing a specific nutrient.

A method to identify cells with a specific phenotype (observable trait) based on their appearance or behavior, often through visual observation or tests.

A mutation that gives a growth advantage under specific conditions, such as resistance to antibiotics, making it easier to isolate.

A mutation that does not provide a growth advantage or even confers a disadvantage, making it harder to isolate.

A technique for creating duplicate plates of colonies, using a velvet pad to transfer cells from a master plate to new plates, allowing for testing on different media.

A technique for transferring colonies to a gridded plate, providing a more systematic and accurate method for identifying mutants.

Mistakes that occur during DNA replication, leading to changes in the genetic sequence. These changes can be detrimental, beneficial, or have no effect on the organism.

Changes in a gene's sequence that don't alter the amino acid sequence of the resulting protein.

Changes in a gene's sequence that result in a different amino acid being incorporated into the protein.

Changes in a gene's sequence that create a premature stop codon, leading to a truncated protein.

Insertions or deletions of nucleotides that shift the reading frame of the genetic code, altering the amino acid sequence.

A mutation that corrects a previous mutation, restoring the original, wild-type phenotype.

Spontaneous mutations highlight that genetic changes can occur randomly without external influences, demonstrating the inherent mutability of DNA.

Restriction enzymes are bacterial proteins that cut DNA at specific sequences, acting as a defense against foreign DNA.

DNA sequences that read the same backwards and forwards, often targeted by restriction enzymes.

Modification enzymes protect a cell's own DNA from being cut by restriction enzymes, preventing self-destruction.

The movement of DNA segments (transposable elements) within or between genomes. These elements can 'jump' to new locations, potentially altering gene function.

A type of transposable element that only encodes the proteins needed for its own transposition. It doesn't carry additional genes.

A transposable element that carries additional genes besides those required for transposition. These genes can have various functions.

A transposition mechanism where the transposable element is copied, and the copy is moved to a new location. This process is like 'copy-pasting' the element.

A transposition mechanism where the transposable element is cut from its original location and pasted into a new location. This process is like 'cut-and-pasting' the element.

The transfer of genetic material from one bacterium to another by a virus (bacteriophage).

A type of transduction where a phage accidentally packages fragments of the host's DNA instead of its own. These fragments can then be transferred to another bacterial cell.

A type of transduction where a phage integrates its DNA into the host genome. If the phage excises incorrectly, it can carry adjacent host genes with it to another bacterial call.

A restriction endonuclease (RE) is an enzyme that cuts DNA at specific sequences called recognition sites. It's like a molecular scissors that can cut DNA in a precise way.

Recombinant DNA is a molecule of DNA that is created by combining DNA from two different sources. Scientists use restriction enzymes and ligase to cut and paste DNA fragments together.

A cloning vector is a DNA molecule, usually a plasmid or a phage, that carries foreign DNA into a host cell for replication and expression. It's like a delivery truck for DNA.

Desirable plasmid traits include an origin of replication (oriV), a selectable marker gene (like antibiotic resistance), a multiple cloning site (MCS), small size, and high copy number. These features make it easier to work with plasmids.

A multiple cloning site (MCS) is a region on a vector with many restriction enzyme recognition sites. It allows researchers to easily insert foreign DNA at specific locations in the vector.

Transformation is a process where bacteria take up foreign DNA directly from their environment. It's like a bacteria swallowing a new piece of DNA.

1. Cut both the vector and the genomic DNA with a restriction enzyme (e.g., BamHI). 2. Mix the cleaved vector fragment and the genomic DNA fragments together and ligate them. 3. Transform the ligation products into E. coli and spread them onto a plate. 4. Select for ampicillin resistance (screening). 5. Imprint ampicillin-resistant colonies onto velvet to screen for tetracycline sensitivity. 6. Incubate the plates and compare the growth to identify recombinant clones. 7. Patch tetracycline-sensitive colonies on agar with starch. Incubate and flood with iodine to check for clear zones, which indicate enzyme activity (starch hydrolysis).

Screening for transformed cells involves identifying bacterial colonies that have successfully taken up a recombinant plasmid containing the gene of interest. This is done by utilizing selectable markers (like antibiotic resistance) and by looking for specific characteristics produced by the inserted gene.

The X-gal system utilizes a specific gene (LacZ) to produce a visual blue/white colony growth pattern. When a gene is inserted into the LacZ gene on a vector, it disrupts the gene's function, leading to a white colony. A functional LacZ gene produces blue colonies.

Shuttle vector plasmids are special plasmids that have multiple origins of replication, allowing them to work in different types of host cells (like bacteria and yeast). They essentially function as a shuttle between different organisms.

Phage vectors are viruses that are used to deliver foreign DNA into bacteria. They carry fragments of DNA within their viral genome and can use the bacteria's machinery for replication and expression.

Cosmids are hybrid cloning vectors that combine the packaging properties of phages with the size capacity of plasmids. They can carry much larger pieces of DNA than traditional plasmids, up to 35-45 kb.

Electroporation is a technique that uses an electric pulse to create temporary pores in cell membranes, allowing foreign DNA entry. It's like a jolt of electricity opening a door for DNA.

A naturally competent bacterium is a bacterium that can naturally take up foreign DNA from its environment. It's like a bacterium with a built-in 'DNA sponge' that can absorb new DNA from the surroundings.

1. Recipient bacteria become competent (able to take up DNA), either naturally or artificially. 2. Donor DNA enters the recipient cell and integrates into the recipient's chromosome. 3. The recipient's original DNA strand is degraded.

Two methods: 1. Treatment with calcium cations (low efficiency) 2. Electroporation (brief electrical pulse). Both make the cell membrane more permeable, allowing DNA to enter.

A type of bacterial transduction where a lysogenic bacteriophage integrates into the host genome and carries specific host genes into recipient cells.

A type of bacterial transduction where lytic bacteriophages accidentally package host DNA and transfer it to recipient cells.

1. Transfer of DNA from cell to cell via direct contact (sex pilus). 2. F plasmid carries genes for sex pilus formation and DNA transfer. 3. F plasmid can integrate into the bacterial chromosome.

1. An F+ cell (containing the F plasmid) uses its sex pilus to connect with an F- cell. 2. One strand of the F plasmid is nicked and transferred to the recipient. 3. Replication occurs in both cells, resulting in two F+ cells.

Hfr strains are bacteria with the F plasmid integrated into their chromosome. They transfer chromosomal DNA at a high frequency during conjugation.

Interrupted mating experiments track the transfer of specific genes based on time. The genes nearest the oriT (origin of transfer) are transferred first and most frequently.

F' plasmids are formed when an integrated F plasmid excises itself, carrying a piece of chromosomal DNA with it. They can transfer this chromosomal DNA to recipient cells.

Transposition is the movement of genetic elements within or between genomes. Transposons are DNA sequences that can move to different locations in the genome.

1. Transposable elements including insertion sequences (IS) and transposons. 2. Transposase enzymes recognize specific sequences to enable transposition. 3. Gene disruption as a result of transposon insertion.

Transposons can disrupt gene functions, which is useful for introducing antibiotic resistance and selecting colonies with desired phenotypes.

A technique used to transfer a recombinant plasmid containing a desired DNA fragment to a recipient cell using a helper plasmid.

1. A recombinant plasmid is constructed with the desired DNA fragment. 2. A helper plasmid with conjugation genes is transferred to an intermediate strain. 3. The intermediate strain transfers the recombinant plasmid to the recipient strain.