Exam 3: Molecular Regulation

Promoter

A specific DNA sequence where RNA polymerase binds to initiate the transcription of a gene.

Pribnow box

A specific consensus sequence (TATAAT) found within the bacterial promoter, essential for initiating transcription.

Leader sequence (5′ UTR)

The region of an mRNA molecule that precedes the coding sequence, involved in regulating gene expression and ribosome binding.

Shine-Dalgarno sequence

A ribosomal binding site in bacterial mRNA that helps align the ribosome with the start codon for protein synthesis.

Start codon

The first codon of an mRNA transcript translated by a ribosome, typically AUG, signaling the start of protein synthesis.

Termination

The final step of transcription where RNA polymerase dissociates from the DNA template and releases the newly synthesized RNA.

Rho-dependent termination

Termination that requires the Rho protein to pull the RNA away from RNA polymerase using ATP.

Rho-independent termination

Termination that does not require an extra protein, relying on a G-C rich hairpin loop followed by uracil residues.

Introns

Non-coding sections of an RNA transcript that are spliced out before translation into a protein.

Exons

Sections of DNA or RNA that code for proteins and remain in the final mature mRNA molecule.

Constitutive expression

Refers to 'housekeeping' genes that are continuously transcribed at a relatively constant rate.

Operon

A cluster of genes under the control of a single promoter, allowing for coordinated regulation.

Operator sequence

A DNA segment within an operon where a regulatory protein binds to inhibit or facilitate transcription.

Regulatory gene

A gene involved in controlling the expression of other genes, often coding for a repressor protein.

Regulatory protein

A protein that binds to DNA to control the transcription of specific genes.

Inducible operon

An operon that is usually 'off' but can be stimulated when an inducer interacts with a regulatory protein.

Repressible operon

An operon that is usually 'on' but can be inhibited when a corepressor binds to a regulatory protein.

Short interference RNA (siRNA)

Small double-stranded RNA molecules that interfere with the expression of specific genes by degrading mRNA.

RISC (RNA-Induced Silencing Complex)

A multiprotein complex that uses a single strand of siRNA to cleave complementary mRNA molecules.

Dicer

An enzyme that cleaves long double-stranded RNA or pre-microRNA into short fragments like siRNA.

Riboswitch

A regulatory segment of mRNA that binds a small molecule, changing the production of the proteins encoded.

Recombinants

Organisms that contain a new combination of genes produced by crossing over or genetic engineering.

Horizontal gene transfer (HGT)

The movement of genetic material between organisms other than by parent-offspring transmission.

Vertical gene transfer

The transmission of genes from an organism to its offspring during reproduction.

Transduction

The process by which DNA is transferred from one bacterium to another by a virus.

Generalized transduction

A process where any bacterial gene can be transferred to a recipient cell.

Specialized transduction

A process where only specific bacterial genes near the viral integration site are transferred.

Conjugation

The transfer of genetic material between bacterial cells by direct contact or a bridge-like connection.

Competent cells

Bacterial cells that can take up extraneous DNA from their environment via transformation.

Bacteriophage

A virus that infects bacteria and reproduces inside them.

Endonucleases (Restriction endonucleases)

Enzymes that cut the DNA phosphodiester backbone at specific internal sequences.

Phosphodiester backbone

The structural framework of nucleic acids, consisting of sugar and phosphate groups linked by covalent bonds.

Vector

A DNA molecule used as a vehicle to carry foreign genetic material into another cell.

CRISPR

A technology that allows for highly specific genome editing.

Spacers

Short segments of DNA memory from previous viral infections stored within the CRISPR locus.

Cas9 endonuclease

An enzyme associated with CRISPR that cuts DNA at a targeted location.

crRNA (CRISPR RNA)

RNA derived from spacers that guides the Cas9 enzyme to matching viral DNA.

Guide RNA (gRNA)

An RNA molecule that directs the Cas9 nuclease to a specific target DNA sequence for editing.