Warm Up 3 2/3 What does DNA replication mean? When does DNA need to make a copy of itself? What does “template” mean?

DNA Replication When cells divide (mitosis), their DNA makes a copy during S phase of the cell cycle

DNA Replication The “original” molecule has two complementary strands

DNA Replication separation of the two strands by helicase forms 2 template strands

DNA Replication Each strand has all the info to make other half because of base pairing New nucleotide attach to original strand

DNA Replication Final Product: 2 DNA’s (each have 1 original and 1 new strand)

DNA polymerase: enzyme that joins nucleotides to make DNA & proofreads new strand Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand After DNA Polymerase is done, other enzymes “proofread” and correct the new strand. The error rate is about 1 error per 10,000,000,000 nucleotide.to Section:

The Race to Discover DNA’s Structure X-Ray diffraction 1952 Rosalind Franklin

Watson & Crick 1953 Developed double helix model

Warm Up 2 1. Look at the difference between a prokaryote cell (left) and an eukaryote cell(right). How do you think the DNA might be different in the two? 11

2. Nitrogen bases are held together by ___________ bonds. 3. What is cell division? 4. Put the following in order: G1 phase, mitosis, G2 phase, S phase, cytokinesis 12

12.2 DNA Length

Prokaryotes 5 million base pairs needs to fit into a space 1/1000 of its length

Eukaryotes 1000 times more DNA than prokaryotes 50-250 million base pairs per cell

proteins called histones which forms nucleosome (bead of histone+DNA). DNA wraps around proteins called histones which forms nucleosome (bead of histone+DNA). Coils to make chromatin. Supercoils to form chromosome. DNA Double Helix Nucleosomes Chromosome Coils Supercoils Histones

DNA Double Helix Nucleosomes Chromosome Coils Supercoils Histones