nucleotides: composition and structure

  1. what are the two types of nucleic acids
    • DNA: deoxyribonucleic acid
    • RNA: ribonucleic acid
  2. what is the function of RNA
    • mRNA: carries genetic information from the nucleus and into cytosol 
    • tRNA: carries the amino acids to ribosomes
    • rRNA (ribosomal RNA): is the structural component of ribosomes where protein is synthesized. 
    • snRNA (small nuclear RNA): component of small nuclear ribonucleoprotein particles which process heterogeneous RNA (hnRNA) into mature mRNA.
    • in viruses, RNA stores genetic information
  3. what is the function of DNA
    stores genetic information used for the synthesis of proteins
  4. what is the primary structure of nucleic acids
    • sequence of nucleotides defines primary structure of DNA and RNA.
    • linked by phosphodiester bonds of 5' carbon to 3' carbon
    • oxygen and nitrogen atoms in the backbone give DNA and RNA "polarity"
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  5. secondary structure of nucleic acids
    • pairing of bases where A-T, G-C by hydrogen bonds
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    • G-C pair: 3 H bonds
    • A-T pair: 2 H bonds
    • The secondary structure of DNA consists of two complementary polynucleotide chains wrapped to form a double helix. Orientation of helix is usually in B-form (right handed with 10 nucleotides per turn). Contain major and minor grooves
  6. what is the most common DNA form
    B-form: right handed with 10 nucleotides per turn
  7. describe complementarity
    C bind with G and A bind with T. Equal number of C to G and equal number of A to T
  8. At what part of the DNA structure does protein and drug interact
    at the grooves were the functional groups on the bases are exposed
  9. What is the secondary structure of RNA
    Consists of a single polynucleotide where folding occurs between complementary regions, resulting in both single and double stranded regions. The strands are antiparallel and assume a helical shape the helices are of the A-form.
  10. what is the structure of tRNA and rRNA
    contains multiple single stranded stem loop structures.
  11. how can DNA and RNA be chemically modified
    via exo and endo nucleases that cleave RNA and DNA via methylation
  12. what are exonucleases
    cleave nucleic acids from the ends
  13. endonucleases
    cleave at specific sequences within or near their sequences. The resulting fragments can be joined to other fragments to create new combinations of DNA sequences
  14. describe the denaturation process of DNA
    DNA can be reversibly denatured enzymatically, chemically, or by heat.
  15. how can heat affect denaturing process of DNA
    • hyperchromic effect: increasing heat breaks the H bonds that holds the strands together and exposes the bases.
    • The higher percentage of GC bonds the higher the Tm required to melt DNA because GC bonds have 3 H bonds compared two 2 hydrogen bonds from AT
  16. what is Tm
    the temperature at which 50% of DNA is denatured
  17. how does renaturing of DNA occur
    Two DNA strands must be in contact to one another initiating base base pairing and must occur when temperature is below Tm
  18. what are the factors that influence renaturing of DNA
    • cations (Na+,K+,Mg2+): decrease repulsion of negatively charged phosphate backbones of two DNA strands.
    • Renaturation only occurs if the temperature is below the Tm
  19. describe how hybridization can occur
    • occurs between nucleic acids from different sources (animals) resulting in a heteroduplex. 
    • heteroduplexes indicates homology of DNA (similarity)
    • DNA and RNA can hybridize with one another to form heteroduplexes.
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nucleotides: composition and structure