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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. How many Nucleotides?.
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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
How many Nucleotides?
The nitrogen containing bases are the only difference in the four nucleotides • Nucleotides can be divided into 2 categories:
Nucleotides • Sugar (Deoxyribose) connects with the phosphate group • 4 Different Bases: • Adenine (A) • Thymine (T) • Guanine (G) • Cytosine (C) • Chargaff’s rules • Rule: A always joins with T • Rule: C always joins with G • Human DNA: ~3 billion pairs 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
DNA 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
Accuracy & Repair A T T A • 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 C G enzyme A C T C G G C
Click here if video won’t play YouTube: DNA Repair Video
ReView • Name the three parts of a DNA nucleotide. • Name the four nitrogen bases and how they pair with others. • Which nitrogen based are pyrimidines? Purines? • 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