DNA

Deoxyribonucleic Acid Defined: Molecule that stores genetic information Monomer: Nucleotide 3 parts to nucleotide 1) Sugar 2) Phosphate Group 3) Nitrogen Base Millions of nucleotides bond to make nucleic acids Deoxyribonucleic Acid

Nucleotides? How many

Sugar (Deoxyribose) connects with the phosphate group 4 Different Bases: Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Rule: A always joins with T Rule: C always joins with G Human DNA: ~3 billion pairs Nucleotides C T A A T G T

Double Helix James Watson and Francis Crick identified DNA’s structure in 1953 Double Helix: spiral shape of DNA Nucleotide strands are connected by a hydrogen bond

DNA Replication Defined: Process of copying DNA During interphase (S-stage) Step 1: DNA Helicase “unzips” the two DNA strands (breaks the H bonds) Step 2: Free floating nucleotides (A, T, C, G) match up Step 3: DNA Polymerase reconnects the two strands

T A A T G C G C A T C G T A A T G C G C C G T A C G A T DNA Helicase polymerase Step 1: DNA Helicase “unzips” the two DNA strands (breaks the H bonds) T A A T G C G C A T C G Both strands are identical Both strands are a mix of old and new nucleotides Step 2: Free floating nucleotides (A, T, C, G) match up T A A T G C G C Step 3: DNA Polymerase reconnects the two strands C G T A C G A T DNA Polymerase DNA Helicase

DNA Replication Video Clip

Accuracy & Repair A T T A T A C G A C T C G G C Mutation: change in DNA sequence Mutations can be corrected Enzyme “proofreads” DNA and check/correct errors Pre-repair: 1 in 10,000 nucleotides has an error Post-repair: 1 in 1 billion nucleotides has an error T A T A C G enzyme A C T C G G C

YouTube: DNA Repair Video Click here if video won’t play YouTube: DNA Repair Video

Review T A G G C C T G T C G A A C A G T Name the three parts of a DNA nucleotide. Name the four nitrogen bases and how they pair with others. Fill in the missing DNA nucleotides: A C ? T ? ? ? G C T ? ? A ? C ? T T ? ? C ? T A T ? ? ? C A ? G ? G ? ? List what takes place during the three stages of DNA replication. Where is the DNA mutation? T A G G C C T G T C G A A C A G T A T C C G G A C A A C T T G T C A