biochem

Initiation

The first step of transcription where RNA polymerase binds to the promoter region of DNA.

Promoter

A specific DNA sequence where RNA polymerase binds during transcription initiation.

Elongation

The stage of transcription where RNA polymerase synthesizes pre-mRNA from the DNA template in the 5' to 3' direction.

Termination

The process at the end of transcription where RNA polymerase detaches after reaching a termination sequence.

pre-mRNA

The initial RNA transcript that undergoes processing before becoming mature mRNA in eukaryotes.

5' Cap

A modification added to the beginning of eukaryotic mRNA for stability and ribosome binding.

Poly-A Tail

A sequence of adenine nucleotides added to the 3' end of eukaryotic mRNA to protect it from degradation.

Splicing

The process of removing introns from pre-mRNA and joining exons together.

Translation

The process of converting mRNA into a polypeptide chain (protein) during protein synthesis.

Cytoplasm

The cellular environment where translation occurs, involving ribosomes.

mRNA

Messenger RNA that carries codons representing amino acids for protein synthesis.

tRNA

Transfer RNA that brings amino acids to ribosomes, possessing anticodons for matching with mRNA codons.

Ribosome

A cellular structure composed of rRNA and proteins where translation occurs.

Start Codon

The AUG codon that signals the beginning of translation and codes for methionine.

Methionine

The first amino acid incorporated into a polypeptide chain during translation.

Peptide Bond

The chemical bond formed between amino acids during protein synthesis.

Stop Codon

A codon (UAA, UAG, UGA) that signals the termination of translation.

Release Factors

Proteins that bind to the stop codon during translation, leading to the release of the polypeptide.

Operon

A cluster of functionally related genes regulated together, typically found in prokaryotes.

Lac Operon

An inducible operon involved in lactose metabolism in E. coli, turned on in the presence of lactose.

Repressor

A protein that binds to the operator region of an operon to inhibit transcription.

Allolactose

A derivative of lactose that binds to the lac repressor, allowing transcription of the lac operon.

Catabolite Repression

A regulatory mechanism that prioritizes glucose metabolism over lactose when both are present.

Trp Operon

A repressible operon involved in the synthesis of tryptophan, normally on but turned off when tryptophan is abundant.

Corepressor

A small molecule (such as tryptophan) that binds to a repressor protein and enhances its ability to inhibit gene expression.

Euchromatin

Loosely packed chromatin that is transcriptionally active.

Heterochromatin

Tightly packed chromatin that is transcriptionally inactive.

Histone Modification

Chemical changes to histone proteins that affect chromatin structure and regulate gene expression.

Acetylation

The addition of acetyl groups to histones, which loosens chromatin and promotes transcription.

Deacetylation

The removal of acetyl groups from histones, which tightens chromatin and represses transcription.

Methylation

The addition of methyl groups to DNA, often leading to silencing of gene expression.

General Transcription Factors

Proteins that assist RNA polymerase in binding to core promoters.

Specific Transcription Factors

Proteins that bind to enhancers and silencers to regulate gene expression.

Mediator Complex

A coactivator complex that helps bridge transcription factors with RNA polymerase.

Alternative Splicing

A process that enables a single gene to produce multiple protein variants by including/excluding specific exons.

RNA Editing

Post-transcriptional modification where nucleotide sequences of mRNA are altered.

mRNA stability

The duration mRNA remains available for translation, influenced by its 5' cap and poly-A tail.

RNA Interference (RNAi)

A biological process where small RNAs (siRNAs and miRNAs) regulate gene expression by degrading mRNA or inhibiting translation.

Phosphorylation

The addition of phosphate groups to proteins, which can alter their activity.

Ubiquitination

A post-translational modification that marks proteins for degradation by the proteasome.

Comparative Gene Regulation

The study of differences in gene regulation mechanisms between prokaryotes and eukaryotes.

Transcriptional Regulation

The process of controlling when and how often a gene is transcribed.

Post-Transcriptional Regulation

Regulation involving mRNA modification, transport, and degradation after transcription.

Translational Regulation

The control of the efficiency and rate of protein synthesis from mRNA.

Post-Translational Regulation

The modification of proteins after their synthesis, affecting their function.

DNA Polymerase III

The main enzyme that synthesizes DNA during replication.

Leading Strand

The DNA strand that is synthesized continuously toward the replication fork.

Lagging Strand

The DNA strand that is synthesized discontinuously, creating Okazaki fragments.

DNA Ligase

An enzyme responsible for sealing Okazaki fragments together into a continuous DNA strand.

3'→5' Exonuclease Activity

The proofreading function of DNA polymerase that removes incorrect nucleotides during DNA replication.

Mismatch Repair Systems

Cellular mechanisms that correct errors missed during DNA replication.

RNA Polymerase

The enzyme responsible for synthesizing RNA from a DNA template during transcription.

Termination Sequence

A specific sequence in DNA that signals RNA polymerase to stop transcription.

Gene Expression

The process by which genetic information is converted into functional products, such as proteins.

Differential Gene Expression

The variation in gene expression levels, allowing for specialization of cells within multicellular organisms.

Chromatin Remodeling

The dynamic change in the structure of chromatin that affects gene accessibility.

Synthesis of RNA Primer

The initial step in DNA replication where primase adds a short RNA strand for DNA polymerization.

Initiator Proteins

Proteins that recognize the origin of replication and recruit other enzymes for DNA replication initiation.

Helicase

An enzyme that unwinds the DNA double helix during replication.

Single-Strand Binding Proteins (SSBs)

Proteins that stabilize unwound DNA strands during replication.

Topoisomerase

An enzyme that alleviates supercoiling of DNA during replication.