Gene Expression and Regulation in Eukaryotes Lecture

Vocabulary flashcards covering major terms and concepts related to eukaryotic gene expression, regulation mechanisms, epigenetics, RNA processing, post-translational control, and comparisons with prokaryotic systems.

Central Dogma

Framework describing information flow: DNA → RNA → Protein

DNA Replication

Nuclear process copying DNA 5'→3' via DNA polymerase

Transcription

RNA synthesis from DNA template by RNA polymerase; includes initiation, elongation, termination

Translation

Protein synthesis on ribosomes using mRNA as template

Chromatin

DNA-protein complex forming chromosomes; equal parts DNA and histones

Nucleosome

Fundamental chromatin subunit: DNA wrapped around an octamer of histones

Euchromatin

Lightly packed, transcriptionally active chromatin

Heterochromatin

Densely packed, transcriptionally silent chromatin

Histone Acetylation

Addition of –COCH₃ to lysines, loosens chromatin, promotes transcription

Histone Deacetylase (HDAC)

Enzyme removing acetyl groups, tightening chromatin, repressing genes

Histone Methylation

Addition of CH₃ groups to histone tails; often condenses chromatin and represses transcription

CpG Island

DNA region rich in CG dinucleotides; target for DNA methylation in promoters

DNA Methylation

Attachment of CH₃ to cytosine in CpG sites; silences gene by blocking TF binding

Epigenetics

Heritable changes in gene expression not involving DNA sequence alteration

Promoter

DNA sequence where RNA polymerase and general transcription factors bind

Enhancer

Distal control element bound by activators to boost transcription

Activator Protein

Transcription factor binding enhancer to increase gene expression

Transcription Initiation Complex

Assemblage of RNA Pol II, TFs, and activators at promoter to start transcription

Proximal Control Elements

Regulatory sequences near promoter influencing transcription

5′ Cap

Methyl-G cap added to pre-mRNA; aids export, stability, and ribosome binding

Poly-A Tail

Adenine stretch at 3′ end of mRNA; enhances export, stability, translation

Spliceosome

RNA-protein complex removing introns from pre-mRNA

Alternative Splicing

Variable exon joining generating multiple proteins from one gene

mRNA Lifespan

Time an mRNA persists; determines amount of protein produced

microRNA (miRNA)

~22-nt ncRNA that degrades or blocks target mRNAs

siRNA

~20-nt double-stranded RNA inducing RNAi gene silencing

Long non-coding RNA (lncRNA)

200-nt RNA with regulatory functions but no coding capacity

Post-Translational Modification

Chemical or proteolytic processing of proteins after translation

Phosphorylation

Addition of phosphate groups to proteins, altering activity

Glycosylation

Attachment of sugars to proteins, affecting folding and targeting

Ubiquitination

Covalent addition of ubiquitin to proteins marking them for degradation

Proteasome

Large protease complex that degrades ubiquitinated proteins

Constitutive Gene Expression

Genes continuously expressed (mostly in prokaryotes)

Inducible System

Gene set turned on by specific signal

Repressible System

Gene set turned off by abundant end-product

RNA Polymerase II

Eukaryotic enzyme transcribing mRNA-coding genes

RNA Polymerase I

Eukaryotic enzyme transcribing rRNA genes

RNA Polymerase III

Eukaryotic enzyme transcribing tRNA and some small RNAs

Naked DNA

Prokaryotic DNA lacking nucleosomes

Nucleosome Packaging

Eukaryotic DNA wrapped around histones

Simultaneous Transcription-Translation

Prokaryotic coupling of the two processes in cytoplasm

Spatial Separation of Expression

Eukaryotic transcription/processing in nucleus, translation in cytoplasm

Mostly OFF Genome

Eukaryotic characteristic where most genes are inactive unless specifically activated