Nucleic Acids

  1. What are nucleic acids?
    • Polymers 
    • DNA, RNA
    • Monomers are nucleotides
  2. Structure of nucleotide. [image]
    Image Upload 1
  3. Describe the structure of a nucleotide.
    • Components joined by condensation reactions:
    • Phosphate 
    • Ester bond
    • Pentose sugar
    • Glycosidic bond
    • Nitrogenous base
  4. What is pentose sugar?
    • A sugar w/ 5 carbon atoms
    • Can either be ribose sugar in RNA or deoxyribose sugar in DNA
  5. What is a polynucleotide?
    • Many nucleotides joined together
    • A repeating sugar-phosphate backbone from which organic bases project
    • Bond between phosphate and sugar is phoD- bond
  6. What are the 5 bases?
    • Cytosine
    • Thymine
    • Uracil (RNA)
    • Adenine
    • Guanine

    A purine will only pair w/ a pyrimidine.
  7. What is complementary base pairing?
    • Hydrogen bonds between pairs of organic bases
    • In DNA, pairing is between adenine-thymine, guanine-cytosine
    • In RNA, pairing is between adenine-uracil, guanine-cytosine
  8. What is the structure of a pyrimidine? 3 bases.
    • The bases grouped into pyrimidines are:
    • Smaller
    • Have a single-ringed structure
    • They are: thymine, uracil, cytosine
  9. What is the structure of a purine? 2 bases.
    • The bases grouped into purines are:
    • Larger
    • Have a double-ringed structure
    • They are: adenine, guanine
  10. What are the features of DNA? Where found, strands, sugar, bases, functions.
    • In the nucleus
    • 2 nucleotide strands:
    • -> twisted into double helix
    • -> linked by H-bonds between bases
    • -> run antiparallel with 3' and 5' ends
    • Sugar-phosphate backbone with deoxyribose sugar
    • Bases: G, C, T, A
    • Function: passes genetic info from cell to cell + gen to gen
    • 3.2 bil base pairs = infinite variety of base sequences, providing genetic diversity
  11. How is the structure of DNA related to its function?
    • Stable structure - passes from gen to gen w/out change, rarely mutates
    • H-bonds - between strands, allows them to separate during replication/p. synthesis
    • Large molecule - carries lots of genetic info
    • Backbone - protects bases
    • Base pairing - allows replication + mRNA
  12. What is a double helix?
    • Two strands of nucleotide
    • Held together by hydrogen bonding
    • Twisted around each other
  13. What are the features of RNA? Where found, strands, sugar, bases
    • Found throughout cell
    • 1 strands -> can be folded into diff shapes
    • Pentose sugar: ribose
    • Bases: G, C, U, A
  14. What does antiparallel strands in DNA mean?
    The strands run in opposite directions.
  15. What makes DNA a stable molecule?
    • PhoD-backbone - protects bases inside helix from external forces
    • Hydrogen bonds - link base pairs, forming bridges between strands
    • -> 3 H-bonds are between C + G so the higher the proportion of C-G pairs, the more stable the DNA
  16. Why is the nature of purine and pyrimidine bonding biologically important?
    • Purines are larger - ensures that polynucleotide strands are equally spaced apart
    • The structure of DNA remains exact and regular - vital since
    • DNA carries the heredity material for an individual
    • DNA can exist as a very long sequence of bases - to carry the large amount of genetic information
  17. Why must DNA replication take place?
    • For mitosis/protein synthesis
    • So daughter cells have genetic info to produce enzymes/proteins they need
  18. Why is DNA replication said to be semi-conservative?
    When 2 new DNA are produced, one of the strands of each helix is from the original DNA and the other is new
  19. Define genetic.
    The inheritance of DNA by daughter cells when a parent cell divides
  20. Distinguish between the functions of DNA, mRNA and tRNA.
    • DNA: carries genetic info inherited from parent DNA
    • mRNA: carries genetic info from nucleus to ribosomes where polypeptides are synthesised
    • tRNA: binds to amino acids + carries them to mRNA combines w/ ribosomes
  21. What are genes?
    • Sections of DNA
    • Control characteristics by coding for proteins through sequences of bases
  22. Define locus.
    The position of a gene on a chromosome
  23. Define allele.
    Different version of a gene
  24. How does a mutation occur in DNA?
    • Bases swap
    • Order of bases changes -> sequence of amino acids changes -> different primary structure -> diff tertiary structure -> changes characteristics
  25. What are the requirements for semi-conservative replication? 5 requirements.
    • The 4 types of nucleotide
    • Both strands of DNA molecule - act as template for attachment of nucleotides
    • Helicase
    • Polymerase
    • Chemical energy
  26. How does DNA replicate? 4 stages.
    • Semi-conservative method
    • DNA helicase breaks hydrogen bonds to separate strands
    • Free nucleotides bind to complementary base pairs on template strands
    • DNA polymerase joins nucleotides in condensation reactions, H-bonds and phoD-bonds form
    • 2 identical DNA molecules are formed, each containing half the original DNA
  27. How would DNA replication be affected if the enzyme polymerase was inhibited?
    • Polymerase joins the 2 strands together
    • If inhibited, DNA molecules would not form
    • DNA replication would slow/stop
Card Set
Nucleic Acids
Topics covered: DNA + RNA structure, DNA replication, energy + ATP, water