Molecular Biology: DNA Replication, Transcription, Translation, and Gene Regulation

Vocabulary practice flashcards covering central concepts of DNA replication, transcription, mRNA processing, translation, bacterial gene regulation, and bioinformatics based on the provided lecture transcript.

Central Dogma

The fundamental concept describing the flow of genetic information in biological systems: DNA is transcribed into mRNA, which is translated into proteins that perform specific cellular functions.

Origin of Replication Initiation (ORI)

Fixed positions on DNA where initiation proteins bind and open the double strands by breaking hydrogen bonds to begin DNA replication.

DNA Polymerase Mechanism

The process by which DNA polymerase synthesizes a new DNA strand in the 5' to 3' direction by catalyzing the covalent linkage of an incoming nucleoside triphosphate to the 3'-OH group, releasing pyrophosphate.

Proofreading

The self-correcting capability of DNA polymerase where it checks whether the previously added base is correct; if incorrect, the base is moved to an editing site, removed, and replaced with the correct base.

Leading Strand

The strand of DNA that is synthesized continuously in the 5' to 3' direction toward the replication fork.

Lagging Strand

The strand of DNA that is synthesized discontinuously in short stretches, known as Okazaki fragments, in the 5' to 3' direction away from the replication fork.

Okazaki Fragments

Short stretches of newly synthesized DNA formed on the lagging strand, each initiated from an RNA primer and eventually joined together.

DNA Helicase

An enzyme that unwinds and opens the double-stranded DNA helix during replication.

Single-Strand DNA-Binding Protein

A protein that binds to single-stranded DNA exposed by helicase, stabilizing it and protecting it from breaking or re-annealing.

Primase

An enzyme that synthesizes short RNA primers required for DNA polymerase to initiate DNA synthesis.

DNA Ligase

An enzyme that joins and seals the backbone of Okazaki fragments together during lagging strand replication.

Telomerase

An enzyme in eukaryotes that prevents chromosome shortening during replication by extending chromosome ends through removing RNA primers and replacing them with DNA.

Promoter

A specific sequence of DNA that serves as the binding site for RNA polymerase and determines where transcription starts.

Operator

A regulatory DNA sequence that controls transcription by binding repressor or activator proteins.

Open Reading Frame (ORF)

A protein-coding DNA or RNA sequence that starts with a start codon (ATG/AUG) and ends with a stop codon (TAA, TAG, TGA in DNA or UAA, UAG, UGA in mRNA).

Terminator

A DNA sequence signal that triggers the termination of transcription.

RNA Capping and Polyadenylation

Eukaryotic mRNA modifications where a 5' cap (modified G with three phosphate groups) and a 3' poly-A tail (150 to 250 adenine nucleotides) are added to mature the pre-mRNA transcript.

Reading Frame

One of three possible ways of reading a sequence of nucleotides continuously as a sequence of non-overlapping codons during protein synthesis.

Aminoacyl-tRNA Synthetase

An enzyme that couples a specific amino acid to its corresponding tRNA molecule, generating the basis of the genetic code.

Lac Operon

An operon in Escherichia coli containing genes (lacZ, lacY, and lacA) controlled by a single promoter and operator involved in lactose uptake and breakdown.

lacZ

A gene in the lac operon that encodes the enzyme $\beta$-galactosidase, which cleaves lactose into glucose and galactose.

lacY

A gene in the lac operon encoding lactose permease, a membrane protein that transports lactose into the cell.

Catabolite Activator Protein (CAP)

A transcriptional activator protein that stimulates expression of the lac operon when bound to cyclic AMP (cAMP) during low glucose conditions.

BLAST

A sequence comparison algorithm used in bioinformatics to search databases, identify homologous DNA or protein sequences, and infer function.

Transcriptional Control Elements

Functional regions of DNA including the Promoter (RNA polymerase binding site), Operator (binding site for repressors/activators), ORF (coding sequence for protein translation), and Terminator (transcription end signal).