Chapter 18

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Chapter 18
2010-12-09 11:22:49
Regulation Gene Expression

Midterm 3
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  1. promoter
    a site where RNA polymerase can bind to DNA and begin transcription
  2. operator
    a switch for controlling transcription; positioned in the promoter or between the promoter and enzyme coding genes, it controls the access of RNA polymerase to the genes
  3. operon
    the entire stretch of DNA required for enzyme production for an enzyme pathway; including the operator, the promoter, and the genes they control (ex: trp operon in E.coli)
  4. repressor
    a protein that can turn of the operon; it binds to the operator and BLOCKS attachment of RNA polymerase to the promoter, preventing trasncription of the genes; the protein is specific for the operator of a particular operon
  5. regulatory gene
    creates individual repressors; expressed continuously so there are always repressor molecules present
  6. corepressor
    a small molecule that cooperates with a repressor protein to switch an operon off (if it binds to the repressor, the operon is turned off)
  7. inducer
    present in the inducible operon (ex: in lac operon, allolactose) and is a small molecule that INACTIVATES the repressor
  8. cyclic amp
    cAMP, a small organic molecule that accumulates when glucose is scarce
  9. activator
    a protein that binds to DNA and stimulates transcription of a gene; ex: CAP
  10. differential gene expression
    the expression of different genes by cells with the same genome, the cause of differences between cell types (ex: not due to different genes being present)
  11. histone acetylation
    when acetyl groups are attached to lysines in the histone tails, neutralizing their positive charges and causing them to no longer bind to neighboring nucleosomes; this results in chromatin having a loser structure, and transcription proteins have easier access to the genes
  12. genomic imprinting
    (in mammals) where methylation permanently regulates expression of either the maternal or paternal allele of particular genes at the start of development
  13. epigenetic inheritance
    inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
  14. control elements
    segments of noncoding DNA that help regulate transcription by binding certain proteins
  15. alternative RNA splicing
    where different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns; regulatory proteins decide on intron/exon choices
  16. proteasomes
    giant protein complexes that recogzine ubiquitin-tagged proteins and degrade them
  17. microRNAs
    small single-stranded RNA molecules that are capable of binding to complementary sequences in mRNA molecules; when proteins attach and form a complex, it can either degrade target mRNA or block its translation
  18. RNA interference (RNAi)
    when you inject double-stranded RNA molecules into a cell they turn off expression of a gene with the same sequence as the RNA
  19. small interfering RNAs (siRNAs)
    similar to miRNAs except the difference is these are formed from longer double-stranded RNA molecules that give rise to MANY siRNAs; cause RNA interference (RNAi)
  20. cell differentiation
    the process by which cells become specialized in structure and function; occurs during embryonic development
  21. morphogenesis
    "creation of form", the physical process that give an organism its shape
  22. cytoplasmic determinants
    maternal substances in the egg that influence the course of early development
  23. induction
    signals such as from one embryonic cell to another as well as contact with cell-surface molecules on neighboring cells and the binding of growth factors secreted by neighboring cells that cause changes in the target cells
  24. determination
    the events that lead to the observable differentiation of a cell; the outcome of determination is determinable cell differentiation; once a cell has undergone determination, an embryonic cell is irreversibly committed to it's final fate
  25. myoblasts
    a type of embryonic progenitor cell that gives rise to myocytes, or muscle cells
  26. pattern formation
    the process of cytoplasmic determinants and inductive signals dictating the organization of tissues and organs in their characteristic locations; spatial organizations in an organism
  27. positional information
    the molecular cues that control pattern formation; controlled by cytoplasmic determinants and inductive signals
  28. homeotic genes
    genes discovered by Edward B. Lewis in drosophila that control pattern formation in the late embryo, larvae and adult
  29. embryonic lethals
    mutations in the phentotype that cause death at early stages of development (making them difficult to categorize/sequence)
  30. maternal effect gene
    a gene that when mutant in the mother, results in a mutant phenotype in the offspring no matter WHAT the offspring's genotype is; also called egg-polarity genes
  31. bicoid
    an embryo whose mother has a MUTANT bicoid gene lacks the front half of its body and has posterior structures at BOTH ends; means "two-tailed"
  32. morphogen gradient hypothesis
    gradients of substances called morphogens establish an embryo's axes and other features of its form
  33. oncogenes
    cancer causing genes; found in retroviruses
  34. proto-oncogenes
    close counterparts of oncogenes that are found in the genomes of humans and other animals; they are the normal versions of the cellular genes and they code for proteins that stimulate NORMAL cell growth and division
  35. tumor-suppressor genes
    genes whose normal products inhibit cell division; the proteins they encode help prevent uncontrolled cell growth
  36. ras gene
    encodes the Ras protein which is a G protein that relays a signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases; the cellular response at the end of the pathway is the synthesis of a protein that stimulates the cell cycle
  37. p53 gene
    tumor-suppressor gene; the protein it makes is a specific transcription factor that promotes the synthesis of cell cycle-inhibiting proteins (if knocked out, can cause uncontrolled growth)