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DNA Biology Lecture Outline Flashcards

Gene Regulation

  • Gene Expression Control: Specialized cells activate only certain genes; housekeeping genes are common to all cells.

  • Gene Expression in Prokaryotes:

    • E. coli adjusts enzyme production based on available nutrients.
    • Operon: Cluster of bacterial genes with a control sequence (e.g., lac operon).

  • Lac Operon:

    • No Lactose: Repressor binds to operator, inhibiting transcription.
    • Lactose Present: Lactose binds to repressor, inactivating it and allowing transcription.
    • Tryptophan binding turns off genes for tryptophan synthesis.

  • Eukaryotic Gene Expression:

    • Each gene has its own promoter.
    • Mechanisms affect expression, speed, and length.
    • Occurs in nucleus (chromatin condensation, mRNA transcription/processing) and cytoplasm (translation, mRNA/protein duration).

  • Chromatin Condensation:

    • Tightly compacted chromatin reduces gene expression.
    • Heterochromatin: Inactive, tightly compacted regions. Example: Barr body (inactivated X chromosome in mammalian females).
    • Euchromatin: Contains active genes.
    • Nucleosome: DNA wrapped around histones; transcription activators displace histones.

  • DNA Transcription:

    • Similar to prokaryotes but with more regulatory proteins.
    • Transcription Factors: DNA-binding proteins that help RNA polymerase bind; can speed up transcription.

  • mRNA Processing:

    • Introns are removed and exons spliced.
    • Alternative mRNA processing: Produces multiple proteins from one gene.

  • mRNA Translation:

    • Cytoplasmic proteins regulate translation.
    • Environmental factors can delay translation.

  • Protein Activity:

    • Some proteins require processing to become active (e.g., insulin).

  • Cell Signaling:

    • Cells send chemical signals to influence other cells.
    • Cell-signaling pathway: Chemical signal binds to receptor, initiates transduction pathway, affects cell.

DNA Technology

  • Genetic Engineering: Modifying an organism's genome.

  • Recombinant DNA (rDNA) Technology:

    • rDNA contains DNA from different sources.
    • Vector: Carrier for foreign gene (e.g., bacterial plasmid).
    • Restriction Enzymes: Cut plasmid and splice in gene.
    • DNA Ligase: Seals gene into plasmid.

  • Insulin Production: Human and plasmid DNA spliced, inserted into bacteria, which produce human insulin.

  • Polymerase Chain Reaction (PCR):

    • Amplifies DNA segments.
    • Requires primers and DNA polymerase.
    • Process involves repeated heating, cooling, and replication cycles.

  • PCR Applications:

    • Evolutionary history, DNA fingerprinting (identifying viral infections, cancer susceptibility, forensic data).

  • DNA Fingerprinting:

    • Uses noncoding DNA with repeated sequences.
    • Repeat number varies among individuals.
    • The greater the number of repeats the longer the segment of DNA.
    • PCR products are run on a gel; segment length determines distance moved.

  • Transgenic Organisms:

    • Contain a foreign gene.
    • Transgenic Bacteria: Produce insulin, human growth hormone, vaccines, degrade pollutants.
    • Transgenic Plants: Insect-resistant, herbicide-resistant, increased yield, produce hormones/antibodies.
    • Transgenic Animals: Express growth hormone, produce pharmaceuticals (gene pharming).

  • Animal Cloning:

    • Donor egg DNA replaced with DNA of animal to be cloned.
    • Egg development stimulated in vitro.
    • Egg implanted in surrogate mother.