Eukaryotic Test 3 Lecture 6

  1. Nucleic Acid (3)
    • Long linear polymers of nucleotides
    • Function primarily in storage & transmission of genetic info (may also have structural or catalytic roles)

    DNA: Deoxyribonucleic Acid, genetic materials

    RNA : Ribonucleic Acid (mRNA, rRNA, tRNA)

    RNA functions in transmission of genetic info from DNA to protein, but may also contain genetic info such as in viruses.
  2. Nucleoside
    NucleoSide is a sugar and a base (without the phosphate)
  3. Chargaff's Rule (9)
    1. Base composition of DNA in the cells of all tissues of an organism is identical

    2. [A]=[T], [G]=[C]

    3. [A]+[T] DOES NOT EQUAL [G]+[C]
  4. Watson-Crick DNA double helix model (12)
    1. DNA molecule composed of 2 chains of nucleotides

    2. 2 chains spiral around each other to form a pair of right-handed helices

    3. 2 chains comprising 1 double helix run in opposide directions (antiparallel)

    4. Sugar-phosphate backbone located on the outside of each strand, while the 2 sets of bases project toward the center

    5. Bases occupy planes that are approx. perpendicular to long axis of molecule & are stacked on top of another. Hydrophobic interactions & van der waals forces between stacked planar bases provide stability for entire molecule

    6. The 2 strands are held together by hydrogen bonds

    7. Distance from phosphorous atom to the center of the axis is 1nm

    8. A pyrimidine is always paired w/a purine

    9. N atoms linked to C4 of cytosine & C6 od adenine are predominantly in NH2 configuration rather than NH (imino) form. O atoms linked to C6 of guanine and C4 of thymine are primarily in keto form

    10. Spaces betwen adjacent turns from 2 grooves of different width (major & minor groove) that spiral around the outer surface of double helix

    11. Double helix makes one complete turn every 10 residues (3.4 nm)

    12. Nucleotide sequences of the 2 strands are always fixed relative to one another (complementary
  5. Functions of genetic material (16)
    1. Storage of genetic information

    2. Replication and inheritance

    3. Expression of the genetic message
  6. DNA Conformation (18)
    1. Relaxed: Supercoiled

    2. Underwound: Negatively supercoiled

    3. Overwound: Positively supercoiled

    Circular DNAs found in nature are invariably negatively supercoiled
  7. Topoisomerases/ Type I Topoisomerases (19)
    Changes the topology of DNA

    Type I Topoisomerases: Changes the supercoiled state of a DNA molecule by creating a transient break in ONE strand of the duplex

    Type I essential for processes such as DNA replication and transcription
  8. Type II Topoisomerases (20)
    Creates a transient break in BOTH strands of the duplex

    Topoisomerase II required to unlink DNA before duplicated chromosomes can be separated during mitosis
Card Set
Eukaryotic Test 3 Lecture 6
Powerpoint 28 (11.05.10)