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.