Chapter 16: The Molecular Basis of Inheritance - You will understand that DNA is genetic material - You will understand that many proteins work together in DNA replication and repair - A chromosome is DNA packed together with proteins

Proof that nucleic acid is what codes phenotypes -Hershey Chase experiment -Concluded that the protein didn’t enter the cell and that DNA is what produces phenotypes Chargaff -Found that Adinine and Thymine occurred in equal amounts in Nucleic Acid -Ratios of C and G also equaled

Structure of DNA -Purines (Guanine, Adinine)-Double Helix -Pyrimidines (Tymine, Cytosine) -Ribose -Hydrogen Bonds-Phosphate Group -Nucleotide-Chargaff’s Rule

What is the driving force behind gene expression? (Quote from Watson and Crick p. 311) -Complimentary base pairs allow for an accurate replication mechanism -Basics of the DNA Replication 1. Double Helix 2. The two strands “unzip” 3. Free nucleotides bond to the parent DNA strands Human Genome -6 billion base pairs -Genome will fill 1,200 AP bio books -Replicated in just a few hours -Errors occur in 1/10 billion base pairs -Most of Replication is known about prokaryotic cells – Eukaryotic is similar to Prokaryotic

Replication Stage 1: Initiation -”Start” DNA sequence -Creates replication bubble -Uses a variety of enzymes Topoisomerase – Relieves stress on rest of Helix Helicase – Untwists the Helix and separates the DNA Single-stranded binding proteins – Stabilize single stranded DNA Primase – adds RNA to the parent DNA and will act as a primer for DNA to form (3’ to 5’)

DNA Polymerase -Speeds up the reaction of a single nucleoside with the new chain -There are many types of polymerases -Phosphate groups are highly reactive -Add to the 3’ end of the new chain

Replication Fork: Solving the Anti-parallel problem in a Bacterial Cell Leading Strand Synthesis -Continuous -Adds in a 5’ to 3’ direction -DNA Poly III is the enzyme that adds the nucleosides Lagging Strand -Has to add in a 5’ to 3’ direction -Needs to use multiple RNA Primers (Use of primase) -DNA Poly III synthesizes nucleoside addition until reaches next Primer -DNA Poly I then replaces the RNA primer with DNA -DNA Ligase connects the Okazaki fragments -Telomeres are repeating DNA units at the end of Chromosomes that help combat the natural shortening of chromosomes due to replication. -Nucleas is an enzyme that cuts out damaged or incorrect DNA pairings

DNA is packaged in a Double Helix Histones are proteins that are made mostly out of positively charged amino acids DNA wraps twice around Histones Histones are linked together by the Linker DNA Supercoils of DNA DNA Packaging