Molecular Genetics

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Author:
HappyJedi7
ID:
143368
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Molecular Genetics
Updated:
2012-03-23 19:03:47
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Bio 244 lab
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Unit 17
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  1. basic structure of DNA
    • polymer composed of repeating units called nucleotides
    • two polynucleotide chains that are linked together by hydrogen bonds between the nitrogenous bases
    • double helix (2 strands run antiparallelI)
    • sugar-phosphate backbones
    • Van der Waals attractions between adjacent stacked bases
  2. a DNA nucleotide consists of 3 components:
    • phosphate
    • 5-carbon sugar (deoxyribose)
    • 1 or 4 different nitrogenous bases
  3. nitrogenous bases
    • double-ringed purines : adenine and guanine
    • smaller, single-ringed pyridimines : cytosine and thymine
    • A=T
    • G=C
    • ratio of (A/T):(C/G) varies from species to species
  4. structure of a nucleotide
    • phosphate bound to 5'C on the deoxyribose molecule
    • nitrogenous base bound to 1'C of the deoxyribose molecule
    • enzyme DNA polymerase attaches the phosphate of one nucleotide (5' end) to the 3'C of th next nucleotide via condensation
  5. DNA strand structure
    • antiparallel
    • 5'-->3' strand runs counter to the 3'-->5' strand
    • 2 ends:
    • * a 3' end with a free hydroxyl group attached
    • * a 5' end with a phosphate group attached
  6. DNA replication
    • occurs prior to mitosis (S phase)
    • an enzyme separates the 2 strands
    • DNA polymerase takes free nucleotides from the cytoplasm and pairs up the nucleotides needed to match the exposed nucleotides of the strand
    • semiconservative DNA replication
    • result is 2 identical copies of DNA
  7. semiconservative DNA replication
    • results in 2 identical copies of DNA
    • each new DNA molecule contains one of the original strands and a newly synthesized complementary strand
  8. RNA differences from DNA
    • RNA is smaller (typically one-stranded)
    • Uracil replaces Thymine
    • sugar component is ribose
    • several forms of RNA (one major form of DNA)
  9. messenger RNA (mRNA)
    carries the complementary strand from DNA in the nucleus to ribosomes in the cytoplasm
  10. transcription
    • process of making an mRNA copy of DNA
    • occurs in the nucleus
  11. RNA polymerase
    • enzyme that transcribes DNA into RNA
    • produces a complementary RNA strand from one of the DNA strands
  12. codons
    • a group of 3 mRNA nucleotides
    • codes for one specific amino acid
  13. ribosome
    • an organelle consisting of rRNA and various proteins
    • "reads" the mRNA message and converts it into a protein
  14. translation
    process of combining a specific number of amino acids together in a specific sequence, as determined by the mRNA sequence
  15. transfer RNA (tRNA)
    • attached to a specific amino acid that matches with the codon
    • enzyme aminoacyl-tRNA synthetase attaches amino acid to tRNA by condensation
  16. anticodon
    a group of 3 nucleotides that are complementary to codons on the mRNA
  17. forming the polypeptide chain (translation)
    the ribosome hydrolyzes the amino acid from the tRNA and attaches it (by condensation) to the polypeptide chain by forming a peptide bond
  18. mutations
    • any change in the DNA
    • base substitutions (silent mutation, missense mutation, nonsense mutation)
    • base deletion/insertion
  19. base substitution
    one nucleotide is replaced by another
  20. silent mutation
    a base substitution does not cause a change in the final amino acid sequence of a protein
  21. missense mutation
    the altered codon still codes for an amino acid, but for a different one
  22. nonsense mutation
    • the altered codon becomes a stop codon; the translation is stopped prematurely
    • creates a nonfunctional protein
  23. base deletion/insertion
    • one or more nucleotides are removed/added, respectively, from the DNA
    • all nucleotides downstream will be improperly grouped into codons, leading to extensive missense
    • nonfunctional protein
  24. replacement of polar/nonpolar amino acids
    • replacing a nonpolar amino acid with another nonpolar amino acid may not affect the function/structure of the enzyme/protein produced (likewise for polar amino acid replacement)
    • replacing a nonpolar amino acid witha polar amino acid may cause a dramatic change in how the protein functions
  25. restriction enzymes
    • used as powerful tools in molecular biology
    • bacterial enzymes that recognize a specific sequence in DNA and cleaves it near that spot (recognition site)
    • creates a blunt or sticky end
    • very specific
    • used to help recognize and destroy foreign DNA (ex phages)
    • act as a primitive immune system
  26. methylation
    • adds methyl groups to nucleotides that could be reconized by restriction enzymes
    • protects bacteria's own DNA from hydrolysis
  27. recombinant DNA
    • DNA ligase can be used to rejoin sticky fragments and seal the strands
    • foreign piece of DNA may thus be incorporated into the DNA
    • if inserted into a bacterium, it can then create the foreign gene products
  28. Smaller pieces of cleaved DNA will behave differently than the original piece when placed into a...
    ... electrophoresis gel.
  29. The procedure of using electrophoresis gel to create recombinant DNA is as follows:
    • DNA digested by restriction enzymes
    • dye is applied to DNA
    • DNA placed into wells in the aragose gel
    • electrical current applied to gel
    • DNA fragments move through the gel
  30. The rate of migration that the pieces of DNA move through the electrophoresis gel is...
    ... inversely proportional to their size.
  31. Nucleic acids carry _____ charges and will move towards the _____ electrodes of the gel.
    negative; positive

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