1. DNA Structure, Nucleotide %s, and Replication

2. DNA Consists of Nucleotides
Sugar Phosphate backbone:
Deoxyribose sugar (Ribose sugar in RNA)
Phosphate Group
Nitrogenous Base (4 types):
Adenine, Thymine, Guanine, and Cytosine.
Purines: Adenine and Guanine
Pyrimidines: Thymine and Cytosine

3. What is DNA’s form? Double helix- Looks like a spiral stair case.
Sugar phosphate backbone never changes, so what part of DNA changes from organism to organism?
Nitrogenous Base order: what causes all of life’s diversity.

4. Building a DNA Model First thing:
Color all the like pieces the same color.
So this means that all the adenine is the same color, guanine is a different color, etc.
Then cut out your pieces and prepare for assembly.

5. DNA STRUCTURE CONNECTED WITH STRONG BONDS
WHAT ARE THE PARTS OF A NUCLEOTIDE?
CONNECTED WITH STRONG BONDS
SUGAR
PHOSPHATE
BASE
These are covalent bonds.

6. DNA STRUCTURE CONNECTED WITH WEAK BONDS (dotted line)
These are called hydrogen bonds.

7. DNA STRUCTURE
How many bases?
How many base pairs?

8. BASE-PAIRING

9. DNA LOOKS LIKE A LADDER

10. DNA LOOKS LIKE A LADDER SUGAR-PHOSPHATE BACKBONE BASES: ADENINE
THYMINE
CYTOSINE
GUANINE

11. Base Pairing Hydrogen bonds connect particular base pairs.
Adenine bonds with Thymine (A=T)
Guanine bonds with Cytosine (G=C)
So purines bond to pyrimidines
Label the DNA strand
Deoxyribose Sugar
Phosphate Group
Nitrogenous Bases
Adenine
Thymine
Guanine
Cytosine
Purines
Pyrimidines

12. How many C’s?
How many G’s?
How many A’s?
How many T’s?

13. If they bond together they must be in equal percentages.
Q: If there is 30% Thymine and 20% Cytosine, how much Guanine and Adenine is there?
A: 20% Guanine
A: 30% Adenine

14. If we know 1 percentage can we determine the rest?
If there is 14% Adenine, what percent Thymine will there be?
Thymine= 14%
What percent Guanine and Cytosine?
Total 100% - (A%+T%) = (C%+G%)
100% - 28% = 72%(G+C)
72%/2 = 36%G and 36%C

15. Sample Question
If the is 28% Guanine, what percent Adenine, Thymine, and Cytosine will there be?
Find Cytosine first (if BP’s with Guanine)
Cytosine = 28%
100% - (28%+28%) = 100% - (56%)= 44%
44%/2 = 22%A and 22%T

16. DNA Replication Follow along and fill in the blanks during this video.

17. DNA Replication Helicase is the enzyme that unwinds DNA.
The parent DNA is used as a template.
DNA polymerase is used to connect complimentary base pairs to the template strand.
New nucleotides join together to make semiconservative DNA.

18. Meselson-Stahl: Semiconservative Replication
Semi: Like a semicircle. What does it mean?
Conservative: To conserve (like the environment). What does it mean?
Why is DNA replication called this?