Mechanisms of Genetic Control and Sequence Variation

Gene Regulation

The process by which cells control which genes are expressed or repressed.

Operon

A group of related genes transcribed together under the control of a single promoter.

Promoter

A specific DNA sequence where RNA Polymerase attaches to begin transcription.

Operator

A DNA sequence that acts as an on/off switch for gene transcription.

Structural Genes

Genes that code for the metabolic enzymes.

Regulatory Gene

A gene that codes for a repressor protein, controlling transcription in an operon.

Inducible Operons

Operons that are usually off and are activated in response to an inducer.

Repressible Operons

Operons that are usually on and are inhibited when a corepressor accumulates.

Histone Acetylation

The addition of acetyl groups to histone tails, making DNA transcriptionally active.

DNA Methylation

The addition of methyl groups to DNA bases, resulting in gene inactivation.

Epigenetics

Heritable changes in gene expression that do not involve changes to the underlying DNA sequence.

Transcription Factors

Proteins that assist RNA polymerase in binding to the promoter to initiate transcription.

Enhancers

Control elements that increase the likelihood of transcription when bound by activator proteins.

Silencers

Control elements that decrease the likelihood of transcription when bound by repressor proteins.

Alternative RNA Splicing

The process of producing different mRNA molecules from the same primary transcript.

Cytoplasmic Determinants

Maternal substances in the egg that influence early development and gene expression.

Induction

Signal molecules from embryonic cells that cause transcriptional changes in nearby target cells.

MicroRNAs (miRNAs)

Small non-coding RNAs that can bind to mRNA and silence gene expression.

Point Mutations

Changes in a single nucleotide pair of a gene.

Silent Mutation

A nucleotide substitution that does not change the amino acid sequence of a protein.

Missense Mutation

A substitution that results in a different amino acid being incorporated into a protein.

Nonsense Mutation

A substitution that creates a stop codon, leading to a truncated, non-functional protein.

Frameshift Mutation

Mutations caused by insertions or deletions that disrupt the reading frame of codons.

Chromosomal Mutations

Large-scale mutations affecting whole chromosomes or large segments thereof.

Neutral Mutations

Mutations that have no effect on an organism's fitness.

Detrimental Mutations

Mutations that negatively affect the function of proteins.

Beneficial Mutations

Mutations that confer a survival advantage and can drive natural selection.