Warm up:

Summarize 12.1Go over 12.2 notes

HW: En’s for 12.1 and 12.3. Fill in key questions on 12.1/12.3Quiz Friday-Chapter 12 DNA ReplicationQuiz Monday-CP8

12.3 DNA ReplicationHow does DNA determine the traits of an organism?

When does DNA replication occur?

A. MitosisB. S phase of interphaseC. ProphaseD. G1 phase of interphase

Steps to DNA replication:

1. DNA’s double helix is “unzipped” by enzyme called helicasea. Breaks apart hydrogen bonds between the base

pairs

Forms two template strands

What is a template?

DNA replication continued

2. DNA polymerase comes in and uses the template strand as a guide to create a complementary strand

a. Uses the base pair rules (G-C, A-T)

Key concept:

The template strand is essential for making sure the daughter strand of DNA contains the same information as the parent strand

What does complementary mean?

The bases on the new strand must be complementary to the bases on the template strand

Write the order of the complementary base strand sequence to the template strand in notesanswer: CGTACG

In ISN

Write the complementary base pair sequence underneath the following template strands:A. GGACC

B. CATGC

C. GAGTA

DNA strands are antiparallelMeaning, they are read in opposite directions

Animations:

http://www.johnkyrk.com/DNAreplication.htmlhttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/micro04.swf::DNA%20Replication%20Fork

Mehelson and Stahl

Wanted to find out how DNA replicated:

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio22.swf::Meselson%20and%20Stahl%20Experiment

DNA Replication is Semi-Conservative

When DNA replicates, half of each new double helix is old DNA (template strand), half is new (complementary strand)Diagraminnotes

Fill in key questions for 12.1/12.3

Closure:

● Why would it be bad if DNA polymerase messed up the order of the nucleotides during replication?

● How would that affect the genetic information being passed on?

● Is the template strand important to help prevent this?