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General Biology II: Gene Expression, Evolution, Classification, and Population Genetics

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Termini in questo insieme (29)

  • Differential gene expression
    Process where cells with the same genome express different sets of genes, producing varied proteins, structures, and functions.
  • Operon
    A cluster of functionally related genes controlled together by a promoter and operator, often transcribed into one mRNA.
  • Lac operon regulation
    Inducible operon for lactose breakdown; repressor blocks transcription without inducer; allolactose inactivates repressor; expression strongest when lactose is present and glucose is low.
  • Trp operon regulation
    Repressible operon for tryptophan synthesis; transcription allowed when tryptophan is scarce; tryptophan acts as corepressor activating repressor to block transcription when abundant.
  • Positive regulation of lac operon
    Low glucose raises cAMP, allowing CAP–cAMP complex to stimulate transcription; high glucose reduces CAP activation.
  • DNA packaging and transcription
    DNA wraps around histones forming nucleosomes; tightly packed chromatin limits gene access; histone acetylation promotes accessibility; DNA methylation often silences genes.
  • Eukaryotic transcription regulation
    Depends on general transcription factors, RNA polymerase, specific activators/repressors, and control elements like enhancers; DNA looping brings distant elements close.
  • RNA processing steps
    Pre-mRNA is processed by adding a 5′ cap, poly-A tail, and splicing out introns; alternative splicing allows multiple protein forms from one gene.
  • Post-transcriptional regulation
    Includes mRNA stability, localization, translation initiation, small regulatory RNAs (miRNAs, siRNAs), protein modification, and degradation.
  • Cell signaling stages
    Reception (signal binds receptor), transduction (signal relay/amplification), and response (cell changes gene expression or behavior).
  • Darwin's theory of natural selection
    Individuals vary in heritable traits; more offspring are produced than resources allow; those with advantageous traits leave more offspring, changing allele frequencies over generations.
  • Fitness in evolution
    Relative reproductive success of an individual in a particular environment.
  • Evidence for evolution: fossil record
    Shows change through time, extinction, and transitions between ancestral and descendant forms.
  • Homologous vs. analogous structures
    Homologous structures share common ancestry; analogous structures have similar functions but evolved independently.
  • Binomial nomenclature rules
    Species name has two parts: genus (capitalized) and specific epithet (lowercase), both italicized; specific epithet alone is not the full species name.
  • Phylogenetic tree branch point
    Represents the inferred common ancestor of the descendant lineages.
  • Clade (monophyletic group)
    A group consisting of a common ancestor and all its descendants.
  • Genetic drift
    Random changes in allele frequencies, especially in small populations, which can fix or eliminate alleles regardless of fitness.
  • Founder effect
    When a new population is established by a small, unrepresentative sample of the original population, causing genetic drift.
  • Hardy-Weinberg equilibrium assumptions
    No mutation, random mating, no natural selection, infinitely large population, and no gene flow.
  • Hardy-Weinberg equations
    Allele frequencies: \(p+q=1\); genotype frequencies: \(p^2+2pq+q^2=1\).
  • Directional selection
    Favors one extreme phenotype, shifting the population distribution toward that extreme.
  • Stabilizing selection
    Favors intermediate phenotypes, reducing variation around the average.
  • Disruptive selection
    Favors both extreme phenotypes over intermediate ones, increasing variation within the population.
  • Gene flow
    Movement of alleles between populations through migration and reproduction, often making populations more similar.
  • Alternative splicing
    Process that joins different combinations of exons to produce multiple mRNA and protein variants from one gene.
  • Role of small regulatory RNAs
    miRNAs and siRNAs guide complexes that inhibit translation or promote degradation of target RNAs.
  • Epigenetic mechanisms
    Heritable changes in gene expression not involving DNA sequence changes, such as DNA methylation and histone modification.
  • Difference between prokaryotic and eukaryotic gene regulation
    Prokaryotes often use operons with coupled transcription and translation; eukaryotes regulate chromatin, process RNA, and separate transcription from translation.