Molecular Biology, Gene Expression, and Evolutionary Principles

Comprehensive vocabulary flashcards covering DNA structure and repair, transcription, translation, mutations, gene regulation via the lac operon, scientific inquiry definitions, and evolutionary mechanisms including natural selection, genetic drift, and speciation.

DNA Polymerase I Proofreading

The enzymatic check for mispairings that occurs as DNA is being made, which is not completely perfect.

Nucleotide Excision Repair

A repair mechanism where the UvrABC complex recognizes DNA damage and cuts out a large chunk of the damaged area, after which DNA polymerase I fills in the gap and DNA ligase seals it.

Mutation

A stable change in DNA resulting from damaged DNA or unrepaired mismatches that cannot be repaired once replication occurs.

Central Dogma of Molecular Biology

The framework describing the flow of genetic information in a cell: DNA to RNA via transcription, and RNA to protein via translation.

Promoter

A specific DNA sequence upstream from where transcription will begin that is bound by RNA polymerase.

Transcription Bubble

A region of locally unwound DNA formed during the initiation of transcription.

Template Strand

The DNA strand that RNA polymerase reads to build a complementary RNA transcript synthesized in the $5' \rightarrow 3'$ direction.

Rho Protein

A protein that tracks behind the transcription bubble in prokaryotes, catching up to RNA polymerase when it stalls at a sequence of many Cs to end transcription.

Introns

Intervening non-coding RNA sequences in eukaryotes that are spliced out during processing.

Exons

Expressed RNA sequences in eukaryotic transcripts that are retained and joined together during RNA processing.

Ribosomal RNA (rRNA)

RNA molecules that serve as structural components of ribosomes.

Transfer RNA (tRNA)

RNA molecules that play a structural role in translation, possessing an amino acid attached to one end and a complementary anticodon at the other.

Messenger RNA (mRNA)

RNA molecules that carry genetic information directly directing protein synthesis.

Codon

A set of 3 nucleotides in mRNA that specifies a single amino acid or signals termination.

Degeneracy of the Genetic Code

The redundancy in the genetic code where most amino acids are specified by multiple codons.

AUG

The start codon that signals the beginning of protein synthesis and encodes the first amino acid, methionine.

Stop Codons

Three specific codons that signal the end of translation and do not encode any amino acid.

Release Factor Protein

A protein that enters the ribosome when a stop codon is reached in mRNA, causing the ribosomal subunits to dissociate and releasing the newly formed protein and mRNA.

Silent Mutation

A point mutation altering a single base pair into a new codon that specifies the exact same amino acid, causing no change in the protein sequence.

Missense Mutation

A point mutation in which a single base pair change results in the substitution of a different amino acid.

Nonsense Mutation

A point mutation that converts an amino acid-encoding codon into a premature stop codon.

Frameshift Mutation

The insertion or removal of a number of nucleotides that is not a multiple of 3, shifting the reading frame and altering all subsequent amino acids.

Operon

A collection of related genes found exclusively in prokaryotes that are transcribed together as a single mRNA molecule.

Lac Repressor Protein

A sequence-specific transcription factor that binds to the operator to physically block RNA polymerase when lactose is absent.

Catabolite Activator Protein (CAP)

A transcription factor that requires cAMP to bind near the promoter, stabilizing RNA polymerase to strongly activate lac operon expression when glucose is low or absent.

Scientific Hypothesis

An explanation with little or no supporting evidence that provides the underlying reason for conducting additional observations and experiments.

Scientific Theory

A broad explanatory framework based on reproducible experimentation and observation that addresses 'how' and 'why' phenomena occur.

Scientific Law

A narrow description based on reproducible experimentation and observation that states 'what' happens, rather than serving as a better-supported theory.

Evolution

A change in the genetic makeup and allele frequency of a population over time across multiple generations.

Natural Selection

The process whereby individuals with traits or alleles that best assist survival and reproduction pass those traits to their offspring, leading to adaptive increases in favorable allele frequencies.

Genetic Drift

The effect of random chance events on a population's gene pool and allele frequencies, having a stronger impact in smaller populations.

Bottleneck Effect

A dramatic and random reduction in population size caused by a natural disaster or catastrophic event, altering allele frequencies or eliminating rare alleles completely.

Founder Effect

A form of genetic drift occurring when a small, randomly selected group of individuals starts a new population in a new region, such as the high frequency of retinitis pigmentation on Tristan da Cunha ($1\text{ in }58$).

Gene Flow

The movement of individuals or gametes that can introduce novel alleles into a population.

Sexual Selection

A mode of nonrandom mating where alleles that enhance an individual's ability to secure a mate are selected for, often resulting in sexual dimorphism.

Hardy-Weinberg Principle of Equilibrium

The principle stating that allele and genotype frequencies in a population remain constant from generation to generation when no evolutionary influences are acting.

Stabilizing Selection

A form of selection where intermediate phenotypes are favored over extremes, such as human birth weight.

Directional Selection

A form of selection where one extreme phenotype is favored over other phenotypes, such as cactus spine length.

Diversifying Selection

A form of selection in which phenotypic extremes are favored over the intermediate traits.

Microevolution

Short-term changes in the genetic structure or allele frequencies of a population.

Macroevolution

Large-scale evolutionary changes occurring across populations over extensive spans of time.

Species

A group of populations whose members have the capability of interbreeding to produce fertile offspring.

Speciation

The evolutionary formation of a new species resulting when separated populations accumulate genetic differences large enough to prevent interbreeding.