DNA Function & Structure

• Stores genetic information

• Double Helix shape

• Chromosomes = DNA wrapped tightly around histones

DNA Structure

• Made of(monomer) Nucleotides

• Nucleotides = sugar, phosphate & nitrogen/nitrogenous base

DNA Structure

• Made of 2 strands

• "Run" in opposite directions

• Antiparallel (like a road)

• 5' to 3' / 3' to 5'

DNA Backbone

• Made of phosphate and sugar

• Phosphodiester bond

DNA Bases

• "Rungs" of the ladder

• 4 Types:

  Adenine, Thymine, Cytosine, Guanine

DNA Bases

• Hydrogen bonds connect bases

• Guanine (G) - Cytosine (C)

  3 hydrogen bonds

• Adenine (A) - Thymine (T)

  2 hydrogen bonds

DNA Bases

• 4 bases put into 2 groups

• Pyrimidines (1 ring):

  Thymine & Cytosine

• Purines (2 rings):

  Adenine & Guanine

DNA Replication

• Semi Conservative:

  keeps half of old and makes half new

• Happens in S phase of cell cycle

• Ensures same amount of DNA is contained in future cells

DNA Replication Enzymes

• 4 Important Enzymes

• Helicase

• Primase

• DNA Polymerase

• Ligase

Helicase

• Breaks hydrogen bonds between bases

• Must happen first

• "unzips" DNA strand

• creates a "replication fork"

Primase

• Tells DNA Polymerase wehre to start

• Places temporary bases

• "air traffic control"

DNA Polymerase

• Places new nitrogen/nitrogenous bases

• "reads" the 3' end

• "inserts" the 5' end

Ligase

• Last enzyme

• "links" new bases in place