Genetics 2

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Genetics 2
2015-03-29 20:52:33

Genetics 2
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  1. 1. Bacteria has how many chromosomes

    2. Humans have how many chromosomes
    Bacteria 1

    Humans 46
  2. Gene Expression
    makes proteins for cellular needs
  3. Regulation of Gene Expression
    Prevents synthesis of enzymes not needed

    Bacteria regulates gene expression at the level of transcription

    Method of regulation: Operon Model
  4. lac operon summary
    Repressor prevents gene expression (polymerase to transcript). when glucose is scarce...the inducer molecule allolactose appears in the cell then binds to repressor molecule and inactivates it. RNA polymerase can now transcribe the operon. three of the lac operon genes get transcribed into Mrna. Ribosomes then bind to Mrna and the three proteins are translated. Beta galactosidase, lactose permease and galactoside transacetylase. The induction of the lac operon enables the bacterium to efficiently transport lactose into the cell and metabolize it.
  5. Beta-galactosidase
    first protein from lac operon. it breaks down lactose into two simple sugars
  6. Permease
    a membrane bound protein (it goes and stays at the cell membrane)

    it embeds into cell membrane. it functions as a direct route for the lactose outside of the cell to come in through
  7. Repressor
    • regulatory proteins that block the ability of RNA polymerase to initiate transcription from
    • repressed genes
  8. Repression occurs as response to
    • overabundance of metabolic end-products & results in decrease of synthesis of enzymes of
    • that product.

    Default position of gene: on
  9. Inducer
    induction of transcription of gene or genes

    -An inducer induces transcription of a gene.

    Default position of gene: off
  10. The Lac Operon
    Contains genes needed to catabolize lactose

    –3 genes coordinately regulated

    • Only expressed when (1) glucose levels
    • are low and (2) lactose is present
  11. Operon is controlled by
    –Repressor & inducer for the repressor (allolactose)

    –Activator (CAP) & inducer for the activator (cAMP)
  12. Mutation
    •Change in base sequence of DNA. Can result in change of end product.
  13. Mutagen
    Environmental agents that bring about mutations
  14. Wild type
    Typical form of an organism as it occurs in nature
  15. Missense mutation
    One base change within a codon

    makes the individual have a different amino acid
  16. Nonsense mutation
    Changes the amino acid into a stop codon. 

    the rest of the amino acids after the stop codon will not be translated. This will result in a nonfunctional protein product
  17. Silent mutation
    Still codes for the same amino acid

    does not affect the product
  18. Frameshift mutation
    Addition or deletion of a base.

    Changes the amino acid sequence that follows. It may or may not become a functional protein.
  19. Ionizing radiation
    –X-rays and Gamma rays

    –Cause breaks in DNA molecule
  20. Nonionizing radiation
    –UV radiation

    –Causes thymine dimers
  21. thymine dimers
    Exposure to ultraviolet light causes adjacent thymines to become cross-linked disrupting their normal base pairing
  22. Repair of DNA Damage
    •DNA polymerase “proof-reading”

    •Thymine Dimer Repair

    1. Light repair using photolyases

    2. Nucleotide excision repair (dark repair)
  23. Light repair
    An enzyme requiring visible light for activity breaks the two bonds joining the two thymines. It goes back to its original shape
  24. Excision repair
    An endonuclease cuts the DNA, and an exonuclease removes the damaged DNA. DNA polymerase fills the gap. DNA ligase seals the gap
  25. The Ames Test
    •Uses Salmonella His- auxotroph

    A test developed for identifying possible carcinogens by studying their mutagenic effect on bacteria

    What is a positive result? (look for answser later)
  26. Vertical gene transfer
    Transmission of genes from parent to offspring
  27. Horizontal gene transfer


  28. Genetic Recombination
    Exchange of genes between 2 DNA molecules to form new combinations of genes