Genetics 2

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  1. 1. Chromosome number in bacteria

    2. Chromosome number in humans
    Bacteria: 1

    Human: 46
  2. Gene Expression

    Make proteins for cellular needs

    • Bacteria regulate gene expression at the
    • level of transcription

    •Method of regulation: Operon Model
  3. Lac operon summary
    When glucose is scarce an inducer molecule Allolactose comes into the cell and binds to repressor molecule inactiving it. cAmp binds to Cap (activator protein) to. RNA polymerase can now transcribe the operon genes. The 3 lac operon genes get transcribed into mRna. Ribosomes then bind to mRna and translates the 3 proteins Beta-galactosides, lactose permease, and galactoside transacetylase. the induction of the lac operon enables the bacterium to efficiently transport lactose into the cell and metabolize it
  4. Beta-galactosides
    protein that breaks down lactose into two simple sugars - glucose and galactose
  5. Permease
    a membrane bound protein

    embeds itself on cell membrane and functions to provide a direct route for the lactose outside the cell to come into the cell
  6. Repressor
    1.regulatory proteins that block the ability of RNA polym to initiate transcription from repressed genes
  7. 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
  8. Inducer
    • induction of transcription of gene
    • or genes.

    • -An inducer induces transcription of a
    • gene.

    Default position of gene: off
  9. 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
  10. Operon is controlled by
    –Repressor& inducer for the repressor (allolactose)

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

    Makes the individual have a different amino acid
  15. 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.
  16. Silent mutation
    It still codes for the same amino acid

    It does not affect the product
  17. Frameshift mutation
    addition or deletion of a base

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

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

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

    •Thymine Dimer Repair

    1.Light repair using photolyases

    2.Nucleotide excision repair (dark repair)
  22. Light Repair
    An enzyme requiring visible light for activity breaks the two bonds joining the two thymine molecules together. They go back to their original shape
  23. Excision repair
    • endonuclease cuts the DNA out
    • exonuclease removes damaged DNA
    • Polymerase fills gap by synthesizing new dna
    • Ligase seals gap
  24. 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? More growth
  25. •Vertical gene transfer
    Transmission of genes from parent to offspring
  26. •Horizontal gene transfer


  27. Genetic Recombination
    Exchange of genes between 2 DNA molecules to form new combinations of genes
  28. Transformation
    transfer of naked DNA into a permeable cell

    ex: floating DNA goes into cell

    recombination occurs
  29. Conjugation
    •Transfer of DNA between 2 bacteria via sex pili

    •Can transfer a plasmid or a portion of the chromosome
  30. Transduction
    •Transfer of DNA between bacteria via Bacteriophage (a virus)
  31. Bacteriophages
    viruses that infect bacteria

    • professor definition:
    • obligate intracellular parasites that will multiply in bacteria using cells machinery

    release virus through budding
  32. F+ cell
    capable of forming sex pili

    • F+ donates plasmid
    • F- cell cannot donate
  33. Plasmids

    •Extra chromosomal DNA

    •Self-replicating, circular DNA molecules

    •May aid bacterial survival
  34. Dissimilation plasmids
    •code for enzymes that allow the catabolism of certain sugars/ hydrocarbons
  35. R factors
    •plasmids that code for antibiotic resistance genes
  36. Stages of a phage infection
    • 1. attachment - random collision
    • 2. entry of genetic material - only have 1
    • 3. synthesis - viral components are being made and then assembled. after assembling it releases through Lysis
  37. Chemical Mutagens
    Chemicals that alter bases

    Nucleoside analogs

    Intercalating agents
  38. F+ conjugation
    A complementary strand to the single stranded plasmid remaining in the donor is synthesized via the Rolling Circle Method. once the single strand is in the recipient cell a complementary strand to the single stranded dna is synthesized. when F+ and F- cells are mixed together eventually all of the cells become F+
  39. Hfr transfer
    When an F factor becomes integrated into the chromosome of an F+ cell, it makes the cell a high frequency of recombination (hfr) cell
  40. Transduction
    • Bacteriophage injects parts of the phage in a cell.
    • New phages are assembled in the cell incorporating pieces of host cell dna
    • The phages are then released through Lysis.
    • The phages inject the dna from donor into a recipient cell. the dna is incorporated into the recipients chromosome
  41. Conjugative plasmid
    the F factor
  42. Spontanous mutations
    • •occurs in the absence of a mutagen or a
    • mutation causing agent
  43. Induced mutations
    •caused by an agent that physically or chemically reacts with the dna
  44. Mutation rate

    Effect of mutagen
    mutation rate: 1 in 10 million genes - rare

    effect of mutagen: depends on type of mutation. Sometimes detrimental to cell. Sometime causes death of cell
  45. Reversion
    • •something causing a mutation and then a
    • chemical reverses the intital mutation
Card Set:
Genetics 2
2015-03-30 06:32:56

Genetics 2
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