Date: March 15, 2016 Aim #61: How does DNA replicate itself? HW: 1)DNA Structure Worksheet 2)All labs due Wednesday!! Please see me if you think you are missing any labs. 3)Human Phys. Unit 7b Packet due Friday (March 18 th ) –Don’t forget Castle Learning! –Human Phys Fridays!! Weekly Human Phys Review in Room 142 with yours truly 4)Genetics Test next Tuesday (p.5) & Wednesday (p.1 & p.7)!! Do Now: Warm-Up Notebook DateTitle of Activity Page # 3/15Nucleotides

Aim #61: How does DNA replicate itself?

1) DNA Replication (Hint) Replicate means to make a copy What does REPLICATE mean?

2) What do we get when DNA replicates? DNA Replication + Two New DNA Molecules

DNA Structure Review What is DNA composed of? Nucleotides 4 types Adenine Thymine Guanine Cytosine Deoxyribose

How do the Bases Pair Up? All Teachers Go Crazy H Bonds

3) DNA Structure What shape is this? Double-Helix What scientists shared the Nobel Prize for their work on DNA? Maurice WilkinsWatson & Crick Rosalind Franklin

Watson and Crick (1953) Double Helix Model: DNA consists of two twisting chains of nucleotides in a ladder-like structure Model Explains: –How DNA replicates and how it is used to make proteins

Maurice Wilkins and Rosalind Franklin used X-ray diffraction to understand the physical structure of the DNA molecule.

5) What Process is Taking Place Here? Cell Division Why do our cells need to divide? GROWTHREPAIR

6) What does the DNA do before a cell divides? Genetic Information (DNA) DNA must replicate before a cell divides 7) Why must DNA replicate itself? DNA is the “Blueprint” for all cell activities. Each cell needs the entire “Blueprint” to function properly.

8) What are the Steps of DNA Replication? G - C C - G T - A A - T T - A DNA Molecule Bonds Broken G C C G T A A T T A 2 Separate Strands Step 1: Bonds between the bases are broken and the DNA Molecule is “Unzipped” Enzymes Helicase

Step 1: “Unzipping” the DNA The bonds between the bases are broken and the DNA molecule is “Unzipped”

What are the Steps of DNA Replication? Step 2: Individual bases find their “match” on each single strand of DNA. G C C G T A A T T A 2 Separate Strands Base Pairing GCTATGCTAT C G A T A CGATACGATA G C T A T Each strand is a Template for base pairing Enzymes DNA Polymerase

What are the Steps of DNA Replication? Step 3: Bonds between the bases are formed G C C G T A A T T A Bonds Formed G - C C - G T - A A - T T - A

DNA Replication G - C C - G T - A A - T T - A DNA Molecule G C C G T A A T T A 2 Separate Strands G - C C - G T - A A - T T - A Bonds Broken Base Pairing What is formed? 2 Identical DNA Molecules

DNA Replication (A Closer Look) Helicase: enzyme that breaks hydrogen bonds holding the two DNA strands together DNA polymerase: only adds nucleotides to the 3’ end continuous mannerLeading strand: DNA strand that is read in the 3’ to 5’ direction but is synthesized in the 5’ to 3’ direction in a continuous manner Lagging strand: made in pieces called Okazaki fragments DNA ligase: links together Okazaki fragments

9) What Process is this? DNA Replication Each strand serves as a Template

SEMI CONSERVATIVE REPLICATION ONE OLD STRAND & ONE NEW STRAND

Summary Questions 1)Do you think DNA Replication is an accurate process? Why? 2)What do you think would happen if DNA did not accurately replicate? 3)What are some of the consequences? 4)DNA Replication AnimationDNA Replication Animation