Bio ch 18 pt 1

Gene Expression

Process of converting DNA into proteins

Transcription

Copying DNA into mRNA

Translation

Creating proteins from mRNA

Eukaryotes

Organisms with complex cells, multiple cell types

Bacteria

Single-celled prokaryotic organisms

Natural Selection

Process favoring advantageous traits

Metabolites

Molecules used in metabolism

Amino Acid

Building block of proteins

Enzymatic Reactions

Chemical reactions catalyzed by enzymes

Tryptophan

Essential amino acid

Biochemical Pathway

Series of chemical reactions in a cell

Operon

Genetic regulatory system in bacteria

Polycistronic mRNA

Single mRNA encoding multiple proteins

Promoter

Region where RNA polymerase binds

Operator

DNA region controlling gene expression

Repressor

Protein blocking gene transcription

Repressible Operon

Usually active, repressed by a repressor

Inducible Operon

Usually inactive, activated by an inducer

Glucose

Simple sugar used for energy

Lactose

Disaccharide sugar found in milk

Galactose

Simple sugar component of lactose

Beta-Galactosidase

Enzyme that breaks down lactose

Permease

Protein aiding in lactose transport

Galactosidase

Enzyme cleaving lactose into glucose and galactose

Lac Operon

Inducible operon for lactose metabolism, repressed by lac repressor

Inducer

Molecule that inactivates repressor to turn operon on

TRP Operon

Repressed in absence of tryptophan, activated by TRP repressor

Catabolite Repression

Reduction of lac operon transcription in presence of glucose

CAP

Catabolite activator protein that enhances lac operon expression

cAMP

Signal for glucose levels affecting lac operon expression

Positive Control

Activation of lac operon by CAP binding near promoter

Corepressor

Molecule binding to repressor to inhibit operon transcription

Adenylyl Cyclase

Enzyme producing cAMP from ATP, inhibited by glucose

Default Condition

Repressor bound to operator, blocking RNA polymerase

Regulatory Gene

Gene encoding repressor separate from operon

E. Coli

Bacterium with operons regulated by repressors and inducers

β-galactosidase

Enzyme produced by lac operon, metabolizing lactose

Glucose Sensing

Mechanism using cAMP levels to regulate lac operon expression

Anabolic Operon

Operon for biosynthesis, repressed by active repressor

Catabolic Operon

Operon for breakdown, activated by inducer or CAP

Protein Composition

Repressor, RNA polymerase, CAP are protein components

DNA Composition

Promoter, operator are DNA components of operons

Gene Expression Regulation

Process of adjusting chromatin to control gene transcription

Chromatin Remodeling

Changing chromatin condensation to regulate gene expression

Euchromatin

Less condensed chromatin, accessible for transcription

Heterochromatin

Highly condensed chromatin, inhibiting transcription

Histone Code Hypothesis

Specific histone modifications influencing chromatin structure

Methylation

Adding a methyl group to nucleotides, affecting chromatin folding

Histone Acetylation

Attaching acetyl groups to histone lysines, loosening chromatin

Epigenetic Inheritance

Inheritance of chromatin modifications influencing gene expression

DNA Methylation

Long-term gene inactivation in cellular differentiation

Histone Deacetylase (HDAC)

Enzyme removing acetyl groups from histones

Chromatin Condensation

Tightening of chromatin structure, leading to silenced genes

Transcription Factories

Specialized areas for gene transcription within the nucleus

Nuclear Lamina

Structure interacting with heterochromatic portions of chromosomes

Eukaryotic Chromosomes

Contain large DNA amounts compacted with proteins

Nucleosomes

Basic unit of chromatin, consisting of DNA wrapped around histones

Telomeres

Chromosome ends with repeated sequences, not coding for proteins

Centromere

Chromosome region with repeated sequences, not coding for proteins

Chromatin Configuration

Adjusting chromatin structure to regulate gene expression

Chromatin Structure

Successive levels of DNA packing in eukaryotic chromosomes

Chromatin Shapes

Variety of confirmations from open to condensed, affecting transcription

Chromatin Modifications

Chemical changes to histones and DNA influencing gene expression

Chromatin Unfolding

Process of making chromatin accessible for transcription

Chromatin Compaction

Process of condensing chromatin, inhibiting gene expression

Chromatin Accessibility

Degree to which chromatin is open for transcription

Chromatin Silencing

Inhibition of gene expression by compacting chromatin