Mutation and Operons Study Guide

Vocabulary flashcards covering point mutations, frameshift mutations, mutagens, somatic vs. germ cell mutations, and bacterial operon regulation mechanisms.

Mutation

A change in the genetic material (DNA).

Point mutation

A change involving one nucleotide in the DNA sequence.

Silent mutation

A mutation where the nucleotide changes, but the same amino acid is produced, usually resulting in no effect on the protein.

Missense mutation

A mutation where the nucleotide changes to produce a different amino acid, which can change the shape and function of the protein.

Nonsense mutation

A mutation where a nucleotide change creates a STOP codon, producing a shortened or truncated protein.

Frameshift mutation

An insertion or deletion of nucleotides that shifts the reading frame, usually changing all codons after the mutation.

Insertion

The addition of a nucleotide to the DNA sequence, which can cause a frameshift.

Deletion

The removal of a nucleotide from the DNA sequence, which can cause a frameshift.

Mutagen

An environmental agent that causes mutations, such as UV radiation or tobacco smoke.

Somatic cell mutation

A mutation occurring in a body cell that affects the individual but is not inherited by offspring.

Germ cell mutation

A mutation in a sperm or egg cell that can be passed to offspring.

Cancer

A disorder where cells lose control of growth and divide uncontrollably.

Sickle cell disease

A disorder caused by a missense mutation in hemoglobin where $Glu \rightarrow Val$, changing a single amino acid.

Operon

A group of genes controlled together under one regulatory system.

Inducible vs. Repressible Operons

Inducible operons are usually OFF and turned ON when needed (e.g., Lac operon), while repressible operons are usually ON and turned OFF when not needed (e.g., Trp operon).

Lac operon

An inducible operon that allows bacteria to use lactose, reaching maximum expression when lactose is present and glucose is low.

Positive regulation (Lac operon)

A control mechanism where low glucose leads to high cAMP; cAMP binds CAP, which then binds DNA to help RNA polymerase transcribe the lac genes.

Allolactose

A molecule produced when lactose is present that binds the repressor, causing it to release the operator so the lac operon can turn ON.

Trp operon

A repressible operon controlling tryptophan production; active when tryptophan is low, and turned OFF when high tryptophan acts as a corepressor to activate the repressor.