Chapter 10 DNA structure and Analysis

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  1. For a molecule to serves as the genetic material, it must be able to:
    • replicate
    • store information
    • express information
    • allow variation by mutation
  2. Proteins were major candidate for genetic material becuase
    • 1940s many geneticists favored proteins
    • proteins are more diverse and abundant in cells
    • subject of the most active areas of genetic research, with more known about proteins than nucleic acid
    • DNA was thought of as too simple to be genetic material and only four types of nucleotides compared to 20 different amino acids
  3. Griffith (1927)
    • showed that avirulent strains of Diplococcus pneumoniae could be transformed to virulence
    • speculated that the transforming principle could be part of the polysaccharide capsule or a compound required for capsule synthesis
  4. IIIS
    • smooth colony
    • virulent
  5. IIR
    • avirulent
    • rough colony
  6. Avery, MacLeod, and McCarty
    demondstared that the transforming principle was DNA and not protein
  7. Hershey and Chase (1952)
    • using E.coli and an infecting virus (bacteriophage T2) demonstrated DNA and not protein was genetic material
    • used radioisotope 32P and 35S
    • demonstrated that DNA enters the bacterial cell during infection and directs viral reproduction
  8. Transfection
    • process of infection by viral DNA into bacterial cells
    • proved conclusively that the viral DNA alone contains all the necessary information for production of mature viruses
  9. UV light
    • DNA and RNA absorb UV light most strongly at 260 nm and UV light is capable of inducing mutations in genetic material at 260 nm
    • This provided strong indirect evidence for DNA as genetic material
  10. Recombinant DNA technology
    • strongest direct evidence for DNA as the genetic material
    • segments of eukaryotic DNA corresponding to specific genes are isolated and spliced into the bacterial DNA
    • complex can be inserted into a bacterial cell and monitored
  11. Tobacco mosaic virus
    demonstrates that RNA serves as the genetic material for these viruses (some viruses have a RNA core instead of a DNA core)
  12. RNA replicase
    replication of viral RNA
  13. Reverse transcriptase
    • Retroviruses replicate in this unusual way
    • RNA serves as template for synthesis of complementary DNA by the RNA dependent DNA polymerase
    • DNA is incorporated into the host cell genome; when transcribe, copies of the original retroviral RNA chromosomes are also produced
  14. Nucleotides
    • building blocks of DNA
    • Consist of nitrogenous base, pentose sugar, and phosphate group
  15. Purines
    • Adenine and Guanine
    • Bicyclic compounds
    • Both have an amine group
    • Guanine has a carbonyl
  16. Pyrimidines
    • Cytosine, Thymine and Uracil
    • Cytosine = one amine group and carbonyl
    • Uracil = two carbonyl groups
    • Thymine = two carbonyls and a methyl group
  17. Nucleoside
    • contains the nitrogenous base and the pentose sugar
  18. Nucleotide
    nucleoside with a phosphate group added
  19. Where is the phosphate group located on the nucleotide?
    Carbon 5
  20. The number of phosphate groups have what effect on nucleotides?
    • their naming system
    • ex. NMPs, NDPs, NTPs
  21. Phosphodiester bond
    • this is how nucleotides are linked to each other
    • they are linked at the carbon 5 and the OH group on the carbon 3 group
  22. Chargaff
    • showed that the amount of A is proportional to T and the amount of C is proportional to G
    • however percentage of CG is not necessarily equal to the percentage of AT
  23. X-ray diffraction
    • studies by Rosalind Frankllin
    • DNA showed 3.4 angstrom periodicity
    • characteristic of helical structure
  24. Watson and Crick
    • proposed that DNA is a right-handed double helix in which two strands are antiparallel and the bases are stacked
    • two strands are connected by AT and GC pairing and there are 10 base pairs per helix turn
  25. How many hydrogen bonds are formed in AT base pairs?
    two bonds
  26. How many hydrogen bonds are formed in GC base pairs?
    three bonds
  27. A DNA
    • slightly more compact than B DNA
    • prevalent under high-salt or dehydration conditions
    • doubtful that it occurs in vivo
  28. B DNA
    • seen under aqueous, low-salt conditions and is believed to be the biologically significant conformation
    • more compact that C DNA, D DNA, E DNA, and P DNA
  29. Z DNA
    forms a left-handed double helix
  30. 3 classes of cellular RNAs that function during expression of genetic information:
    • messenger RNA (mRNA)
    • ribosomal RNA (rRNA) makes up 80%
    • transfer RNA (tRNA)
  31. rRNA
    structural components of ribosomes for protein synthesis
  32. mRNA
    template for protein synthesis
  33. tRNA
    carry amino acids for protein synthesis
  34. Nucleic acid can be separated by
    gradient centrifugation procedures
  35. Sedimentation equilibrium centrifugation
    • separates by density gradient
    • bouyancy
  36. Sedimentation velocity centrifugation
    measures the velocity of sedimentation in Svedberg coefficient units
  37. Hyperchromic shift
    • during DNA denaturation
    • used to determine the melting temperature (Tm)
  38. Melting temperature
    method for estimating the base composition of DNA
  39. Molecular hybridization
    • denaturation and renaturation of nucleic acids
    • increased understanding of gene transcription
    • refinements have helped advance study of molecular evolution and organization of DNA in chromosomes
  40. Fluorescent in situ by hybridization (FISH)
    • uses fluorescent probes to monitor hybridization
    • can be used to identify the chromosomal location of a DNA of interest
    • ex. DNA specific to the centromeres of human DNA
  41. Reassociation kinetics
    • analyzes rate of reassociation of complementary single DNA strand
    • provides information about he size and complexity of genomic DNA from an organism
  42. Nucleic acid electrophoresis
    separates RNA and DNA fragments by size such that smaller fragments migrate through a gel at a faster rate than large fragments
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Chapter 10 DNA structure and Analysis
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