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Chapter 5: Genetics

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Termini in questo insieme (21)

  • Genotype vs Phenotype

    Genotype is the genetic makeup of an organism, while phenotype is the observable physical or physiological traits influenced by the genotype.

  • Differences between Prokaryotic and Eukaryotic Genomes

    Prokaryotes have few, usually circular chromosomes in the nucleoid region, organized by histone-like proteins. Eukaryotes have many linear chromosomes in a nucleus, organized by histones.

  • Basic Structure of a Nucleotide

    A nucleotide consists of a phosphate group, a sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base (A, T/U, G, C).

  • Base Pairing Rules in DNA

    In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C) via hydrogen bonds.

  • DNA Directionality

    DNA strands have chemical directionality: one end has a 5' phosphate group and the other a 3' hydroxyl group; DNA is synthesized 5' to 3'.

  • Antiparallel Nature of DNA

    DNA is double-stranded with strands running in opposite directions: one 5' to 3', the other 3' to 5', allowing complementary base pairing.

  • Differences between DNA and RNA

    RNA contains ribose sugar, uracil instead of thymine, is usually single-stranded, and can fold into complex structures.

  • Central Dogma of Molecular Biology

    Genetic information flows from DNA to RNA (transcription) and from RNA to protein (translation).

  • Key Enzymes in DNA Replication

    Helicase unwinds DNA; primase synthesizes RNA primers; DNA polymerase III synthesizes new DNA; DNA polymerase I replaces RNA primers; ligase seals DNA fragments; gyrase/topoisomerase relieve supercoiling.

  • Leading vs Lagging Strand Synthesis

    Leading strand is synthesized continuously toward the replication fork; lagging strand is synthesized discontinuously away from the fork in Okazaki fragments.

  • Role of RNA Primers in DNA Replication

    RNA primers provide a 3' OH group for DNA polymerase to begin DNA synthesis.

  • Steps of Transcription

    Initiation: RNA polymerase binds promoter; Elongation: RNA strand synthesized 5' to 3'; Termination: RNA polymerase detaches at termination sequence.

  • Types of RNA and Their Functions

    mRNA carries codons for amino acids; tRNA carries amino acids and has anticodons; rRNA forms ribosomes.

  • mRNA Splicing in Eukaryotes

    Introns are removed and exons joined by spliceosomes to produce mature mRNA for translation.

  • Genetic Code Features

    64 codons encode 20 amino acids plus start and stop signals; the code is redundant, protecting against mutations.

  • Steps of Translation

    Initiation: ribosome assembles at start codon; Elongation: amino acids added; Termination: ribosome releases protein at stop codon.

  • Operons in Prokaryotic Gene Regulation

    Operons are clusters of genes controlled by a single promoter and operator; inducible operons are off by default, repressible operons are on by default.

  • Quorum Sensing

    Bacteria communicate via chemical signals to regulate gene expression based on population density, important for biofilm formation.

  • Types of Mutations

    Substitution changes one base; insertion adds bases; deletion removes bases; effects include silent, missense, nonsense, and frameshift mutations.

  • DNA Repair Mechanisms

    Excision repair removes damaged DNA sections; DNA polymerase fills gaps; ligase seals backbone; proofreading by DNA polymerase reduces errors.

  • Horizontal Gene Transfer Methods

    Includes conjugation (plasmid transfer via pilus), transformation (uptake of free DNA), transduction (phage-mediated DNA transfer), and transposons (mobile genetic elements).