Lecture 11 Review

1
Lecture 11 Review

• DNA is the material of heredity
• Consists of 4 nucleotides joined between the 3
  carbon of the deoxyribose group of the first
  nucleotide and the phosphate group of the next
  nucleotide (which is attached to the 5 carbon of
  deoxyribose)
• Direction 5 to 3
• Structure double stranded helix
• A pairs with T G pairs with C

2
DNA in the nucleus

• Compacted by interactions with proteins
• (1) nucleosomes are formed by DNA interactions
  with histones H2A, H2B, H3, and H4
• (2) histone H1 helps nucleosomes interact with
  each other
• (3) this form of DNA forms loops some portions
  interact with scaffold, such as the nuclear matrix

3
Contd

• Heterochromatin highly compacted DNA
• Facultative heterochromatin is highly compacted
  in some cells and not in others
• Euchromatin not so tightly compacted DNA
  (actively transcribed genes)
• Metaphase chromosomes very highly compacted

4
DNA replication

• (1) helicase, topoisomerase, ssBP
• Opens up DNA and prepares it for replication
• (2) primase adds in short stretches of RNA to
  act as primers
• (3) DNA polymerase III adds deoxyribonucletides
  to the 3 end of the RNA primers
• Direction of synthesis is 5 to 3

5
Contd

• Leading strand synthesis vs. lagging strand
  synthesis..
• Okazaki fragments