NOTEBOOKS DUE IN 20 MINS Set up Cornell Notes on pg. 93 Essential Question: Explain the base-pairing rules. How many types of nucleotides are there? How do they differ? 8.2 Structure of DNA 2.1 Atoms, Ions, and Molecules Explain the base-pairing rules. How many types of nucleotides are there? How do they differ? Key Concept:DNA structure is the same in all organisms NOTEBOOKS DUE IN 20 MINS

KEY CONCEPT DNA structure is the same in all organisms.

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 base Draw and label on p.92 base phosphate group deoxyribose (sugar) nitrogen-containing base 1 3 2 backbone Covalent bonds

Thymine- T Adenine- A Guanine- G Cytosine-C The nitrogen containing bases are the only difference in the four nucleotides. BASES Thymine- T Adenine- A Guanine- G Cytosine-C

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. bases backbone

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.

Nucleotides always pair in the same way. A pairs with T C pairs with G the helix has a uniform width. Ex: ladder C G T A

The backbone is connected by covalent bonds. The bases are connected by hydrogen bonds. Hydrogen bond hydrogen bond covalent bond backbone Bases (A,T,G,C)

A T C G G C T A T A G C

GATTACAATCGATCGAT CTAATGTTAGCTAGCTA TAGGACTACTAGTCGTA Using the base pairing rules- complete the DNA strand: GATTACAATCGATCGAT CTAATGTTAGCTAGCTA TAGGACTACTAGTCGTA ATCCTGATGATCAGCAT

Have Your DNA & Eat It Too Adenine (A) = Green Thymine (T) = Pink Cytosine (C) = Yellow Guanine (G) = Orange ONLY GET 6 of each marshmallow

A = red B = dark blue C = green D = yellow E = orange F = light blue DNA Coloring Activity Color Key: A = red B = dark blue C = green D = yellow E = orange F = light blue G = brown