FUck Bio

Chapter 11: Gene Regulation and Expression

  • Inducible vs. Repressible vs. Constitutive Genes:

    • Inducible genes are usually off but can be turned on (e.g., lac operon).

    • Repressible genes are usually on but can be turned off (e.g., trp operon).

    • Constitutive genes are always on, regardless of external factors (e.g., genes involved in basic cell functions).

  • Transcription Factors: Proteins that regulate gene expression by binding to DNA and influencing transcription. They allow cells to respond to internal and external signals, enabling differentiation in multicellular organisms.

  • Gene Expression in Bacteria: Bacteria regulate gene expression to conserve energy by turning on genes only when needed (e.g., the lac operon uses energy only when lactose is present).

  • Lac Operon System: A model for gene regulation in bacteria. The operon controls the breakdown of lactose and includes a promoter, operator, and structural genes (lacZ, lacY, lacA). It is transcribed at high levels when lactose is present and glucose is absent.

  • Comparing Lac and Trp Operons: The lac operon is inducible (activated by lactose), while the trp operon is repressible (turned off when tryptophan is abundant).

  • Feedback Inhibition vs. Transcription Regulation: Feedback inhibition is a faster, reversible process, while transcription regulation is a longer-term mechanism that controls gene expression more precisely.

  • Histone Acetylation/Deacetylation: Histone acetyltransferases add acetyl groups to histones, opening chromatin for transcription. Histone deacetylases remove acetyl groups, closing chromatin and silencing transcription.

  • DNA Methylation: The addition of methyl groups to DNA, usually at CpG sites, represses gene expression. This is an important form of epigenetic regulation.

  • Epigenetics: Modifications like histone acetylation and DNA methylation can influence gene expression without changing the DNA sequence itself.

  • Chromatin Types:

    • Euchromatin is loosely packed and active.

    • Heterochromatin is tightly packed and inactive.

  • Barr Body and X-Inactivation: The Barr body is the inactive X chromosome in female mammals. X-inactivation, as seen in calico cats, randomly inactivates one of the X chromosomes in each cell.

  • Alternative Splicing: A process where different exons are combined in various ways to produce multiple proteins from a single gene.

Chapter 12: Molecular Techniques and Genomics

  • PCR: Polymerase chain reaction amplifies DNA by repeating cycles of denaturation, annealing, and elongation. Sanger sequencing differs in that it reads the DNA sequence.

  • Omics Technologies:

    • Genomics studies the entire genome.

    • Transcriptomics focuses on RNA expression.

    • Proteomics studies proteins.

    • Metabolomics examines metabolites in cells.

  • Essential Genes: Genes necessary for basic cellular functions, such as those involved in metabolism or cell division.

  • Metagenomics: The study of genetic material from environmental samples, providing a more comprehensive understanding of microbial communities compared to traditional sequencing.

  • Transposons: Mobile genetic elements used to disrupt genes and study their functions.

  • Orthologous vs. Paralogous Genes:

    • Orthologs are genes in different species that evolved from a common ancestor.

    • Paralogs are genes within the same species that arose through duplication.

  • Repetitive Sequences in Eukaryotic Genomes: These sequences, such as transposons, are important for genome stability and evolution.

  • SNPs: Single nucleotide polymorphisms are variations in a single DNA base and can be used to study genetic diseases or personalize medicine.

Chapter 13: Evolution and Natural Selection

  • Evolution: The process by which populations change over time through mechanisms like natural selection.

  • Theory vs. Hypothesis: A scientific theory is a well-substantiated explanation, while a hypothesis is a testable prediction.

  • Darwin's Observations: Darwin’s voyage on the HMS Beagle led him to understand the diversity of species and the concept of natural selection.

  • Lamarck’s Theory: Lamarck proposed that organisms could pass on traits acquired during their lifetime, a concept now discredited in favor of Darwin's theory.

  • Variation and Natural Selection: Genetic variation is crucial for natural selection, as it provides the raw material for evolutionary change.

  • Artificial vs. Natural Selection: Artificial selection is human-directed breeding, while natural selection occurs in nature based on environmental pressures.

  • Evidence for Evolution:

    • Comparative Anatomy: Homologous structures indicate common ancestry.

    • Embryology and Fossil Record: Provide further evidence of evolutionary relationships.

  • Mutation: Mutations introduce new genetic variation. Even though they occur at a low rate, they are essential for evolution.

  • Gene Pool and Allele Frequencies: The gene pool is the total genetic material in a population, and allele frequencies describe how often different genetic variants appear.

  • Types of Selection:

    • Stabilizing Selection: Reduces variation and favors the average phenotype.

    • Directional Selection: Shifts the population toward one extreme.

    • Disruptive Selection: Increases variation and may lead to two distinct phenotypes.

  • Genetic Drift: Random changes in allele frequencies due to chance, with greater effects in smaller populations.

  • Bottleneck and Founder Effect: Events that drastically reduce population size can lead to genetic drift and reduced genetic diversity.

  • Sexual Selection: A form of nonrandom mating where traits that improve mating success are favored.