1. DNA & Replication
IN 91 & 93
Headings
Vocabulary
Important Words

2. NUCLEUS
CHROMOSOME
CHROMATIN
DNA

3. (DeoxyriboNucleic Acid)
Structure of DNA
(DeoxyriboNucleic Acid)
Using critical info from the work of others (Rosalind Franklin & Linus Pauling)…
James Watson & Francis Crick made 1st model of DNA in 1953
DNA is a Nucleic Acid (AKA: Organic Compound)
DNA is made up of small subunits called: Nucleotides

4. “YES, THE ENTIRE PICTURE!!!”
DRAW THIS IN YOUR NOTES!
“YES, THE ENTIRE PICTURE!!!”

5. What Makes Up DNA? Each nucleotide is made up of: Deoxyribose (sugar)
Phosphate group (“P”)
Nitrogen Base (4 types)
Adenine- A
Thymine-T
Cytosine- C
Guanine-G
Purines
Pyrimidines
Pyrimidines
Purines

6. What Is the “Ladder”? 2 long chains of nucleotides
Joined together in the form of a ladder
Ladder is twisted in the form of a double helix or spiral

7. Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)

8. Sides of the Ladder =
Alternating Deoxyribose (Sugar) & Phosphate
s-P-s-P-s-P-etc.
Rungs or Steps of ladder =
Pairs of Nitrogen Bases
A-T or C-G
T-A or G-C

9. How Do Nitrogen Bases Pair Up?
Adenine(A) pairs up w/ Thymine(T)
Guanine(G) pairs up w/ Cytosine(C)
Example:
A G C T A C G C A 5’ 3’ 3’
A T G
C G T 5’
T C G

10. Why Do Organisms Look So Different?
All organisms have the same type of nucleotides
Nucleotide arrangement provides for all the different types of organisms
Ex: A mouse and a rosebush have the same nucleotides…but…
Different Nucleotide Order = Different Organism!!!
*This sequence of nucleotides = GENETIC CODE

11. Replication of DNA During cell division a copy of DNA must be made
When new cells are formed each new cell gets an exact copy of the genetic information.
This copy of DNA is made through a process known as Replication.

12. Let’s see DNA Replication at Work!

13. Steps of Replication
During replication, each strand serves as a pattern to make new DNA molecule.
The 2 nucleotide strands separate at base pairs.
They unzip like a zipper using DNA Helicase (enzyme)
Each strand then builds its opposite strand by base pairing with nucleotides that float freely in the nucleus.
Each new DNA molecule has 1 nucleotide strand from the original DNA molecule and 1 nucleotide strand made from free nucleotides in the nucleus.

14. DNA Replication Original strand DNA polymerase New strand Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand