1. DNA
Structure

2. DNA Structure Big Idea of Biology: Structure is related to Function.
DNA Function:
Instructions for making proteins—tens of thousands of proteins
A way to pass the instructions to offspring
How does its structure make this happen?

3. DNA is made of nucleotide building blocks
Each nucleotide consists of:
Phosphate group – PO3-
Pentose sugar – 5 carbon
Nitrogenous base – contains nitrogen

4. Nucleotides
Phosphate
Nitrogenous
Base
Pentose
Sugar

5. 4 Types of Nucleotides A
Adenine T
Thymine C
Cytosine G
Guanine

6. How are these nucleotides connected?
Scientists played around with potential structures, like playing with Legos, to figure it out

7. Important Discovery! What does this indicate?
Species are different in the pattern of bases
The amount of A matches the amount of T and the amount of C matches the amount of G

8. Nitrogen bases have to pair a certain way!
Each base will only bond with one other specific base.
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Form a base pair.
Form a base pair.

9. But how could the nucleotides fit together?
Double helix:
Two connected strands with sugar-phosphate background on outside and base pairs connected on the inside
Another important discovery!

10. Double helix

11. Why do bases pair like this?
To fit:
A 2-ring base has to pair with a 1-ring base
To allow hydrogen bonding:
A and T: 2 bonds
C and G: 3 bonds

12. DNA Structure
Because of this complementary base pairing, the order of the bases in one strand determines the order of the bases in the other strand.

13. A C T G G A T C

14. Build your own DNA molecule
Twizzlers = Sugar-Phosphate backbone
Marshmallows = Nitrogen bases
Green = Guanine
Orange = Cytosine
Pink = Adenine
Yellow = Thymine
Toothpicks to hold it together
Space your DNA so it has 8 base pairs: when your molecule is finished, twist it to see what it looks like as a double helix