Molecular Biology: Lac Operon Quiz

Genes that are constantly expressed at a fixed rate, regardless of environmental conditions.

Genes that are only expressed when needed, responding to specific environmental cues.

Genes that code for proteins that perform specific functions in the cell.

Genes that regulate the expression of other genes, controlling when and how much protein is produced.

A cluster of genes that are transcribed together as a single unit, controlled by a single regulatory element.

A DNA sequence that a repressor protein binds to, blocking transcription of the genes in the operon.

A mechanism that regulates gene expression by preventing transcription. A repressor protein binds to the operator, blocking RNA polymerase.

A mechanism that regulates gene expression by stimulating transcription. An activator protein binds to the operator, enhancing RNA polymerase binding.

A regulatory protein that binds to DNA and activates transcription.

The default state of a repressible operon is ON, meaning gene expression is occurring unless a repressor protein binds to the operator and blocks transcription.

The default state of an inducible operon is OFF, meaning gene expression is not occurring unless an inducer molecule binds to the repressor protein, causing it to detach from the operator and allowing transcription to proceed.

A group of genes that regulate the transport and metabolism of lactose in E. coli.

A single mRNA transcript that includes multiple coding sequences for different proteins.

An enzyme that breaks down lactose into glucose and galactose.

A protein that helps transport lactose across the cell membrane.

A molecule that serves as a cellular alarm signal, indicating low glucose levels.

A change in the nucleotide sequence of DNA that can alter the amino acid sequence of a protein and potentially the phenotype of a cell.

Mutations that occur due to external factors like radiation or chemicals.

Mutations that happen spontaneously without external intervention.

A point mutation is a change in a single base pair within the DNA sequence.

A type of point mutation where the altered codon still codes for the same amino acid, leading to no change in the protein's function.

A type of point mutation where the altered codon codes for a different amino acid, potentially causing a change in the protein's function.

A type of point mutation where the altered codon signals the end of protein synthesis, resulting in a shortened protein.

A point mutation where a single base pair is replaced with a different base pair, resulting in a change in the amino acid sequence of the protein.

A base substitution where a purine base (A or G) is replaced with another purine, or a pyrimidine base (C or T) is replaced with another pyrimidine.

A base substitution where a purine base (A or G) is replaced with a pyrimidine base (C or T), or vice versa.

A mutation that occurs due to the insertion or deletion of one or more base pairs in the DNA sequence, shifting the reading frame of the genetic code.

A mutation that reverts a previous mutation, restoring the original DNA sequence.

The process of correcting mistakes or errors in the DNA sequence, ensuring the integrity of the genetic information.

A mutation that occurs when a nucleotide base mispairs with a non-complementary base during DNA replication.

A test that uses bacteria to determine if a chemical is a mutagen, a substance that can damage DNA and cause mutations.

A bacterial strain that cannot synthesize a specific nutrient, making it dependent on an external source of that nutrient.

A mutation that reverses the effect of a previous mutation, restoring the original phenotype.

A bacterial strain that lacks the ability to synthesize histidine, requiring it to be provided in the growth medium.

A bacterial strain that has regained the ability to synthesize histidine.

A process where a chemical is converted by enzymes into a more reactive form that can damage DNA.

The rate at which a substance causes mutations in a sample of his- cells.

Rat liver extract contains various enzymes that can activate chemicals into their mutagenic forms.

The process of transferring genetic information from one prokaryotic cell to another through free DNA.

The ability of a cell to take up and incorporate free DNA from its environment.

Transfer of DNA between prokaryotic cells mediated by a bacteriophage (virus that infects bacteria).

The direct transfer of DNA from one bacterium to another, requiring physical contact between the cells.

DNA that enters a cell through horizontal gene transfer may get broken down by cellular enzymes.

DNA that enters a cell through horizontal gene transfer can replicate independently if it has its own origin of replication.

DNA that enters a cell through horizontal gene transfer can integrate into the host chromosome, changing the host genome.

The transfer of genetic material from parent to offspring; the most common way genetic information is passed on in organisms.