8.2 structure of dna set up cornell notes on pg. 67 topic: 8.2 structure of dna essential question:...

8.2 Structure of DNA

•Set up Cornell Notes on pg. 67

•Topic: 8.2 Structure of DNA

•Essential Question:

Explain the base-pairing rules. How many types of nucleotides are there? How do they differ?

•Don’t forget to add it to your T.O.Contents!

2.1 Atoms, Ions, and Molecules

Explain the base-pairing rules. How many types of nucleotides are there? How do they differ?

8.2 Structure of DNA

Key Concept:DNA structure is the same in all organisms

8.2 Structure of DNA

KEY CONCEPT DNA structure is the same in all organisms.

8.2 Structure of DNA

DNA is composed of four types of nucleotides.• Each nucleotide has three parts.

1. a phosphate group

2. a deoxyribose sugar

3. a nitrogen-containing basephosphate group

deoxyribose (sugar)

nitrogen-containingbase

1

2

3

Covalent bonds

base

backbone

8.2 Structure of DNA

• The nitrogen containing bases are the only difference in the four nucleotides.

•Thymine- T

•Adenine- A

•Guanine- G

•Cytosine-C

BASES

8.2 Structure of DNA

8.2 Structure of DNA

Watson and Crick determined the three-dimensional structure of DNA by building models.

• They realized that DNA is a double helix– backbone on the outside– bases on the inside.

backbone

bases

8.2 Structure of DNA

• Watson and Crick’s discovery built on the work of Rosalind Franklin and Erwin Chargaff.

– Franklin’s x-ray images suggested that DNA was a double helix of even width.

– Chargaff’s rules stated that A=T and C=G.

8.2 Structure of DNA

TAC

G

Nucleotides always pair in the same way.

• the helix has a uniform width.– Ex: ladder

– A pairs with T

– C pairs with G

8.2 Structure of DNA

• The backbone is connected by covalent bonds.

hydrogen bond covalent bond

• The bases are connected by hydrogen bonds.

backbone

Hydrogen bond

Bases (A,T,G,C)

8.2 Structure of DNA

A

T

CC G

ATG

A

T

G C

8.2 Structure of DNA

GATTACAATCGATCGATCTAATGTTAGCTAGCTA

TAGGACTACTAGTCGTA

ATCCTGATGATCAGCAT

Using the base pairing rules- complete the DNA strand:

8.2 Structure of DNA

Adenine (A) = GreenThymine (T) = PinkCytosine (C) = YellowGuanine (G) = Orange

Have Your DNA & Eat It Too

* I need to check your work before you eat the DNA!!!!!