Objective: What is the structure of DNA? Do Now: Take out your HW and notes 4

Watson and Crick Modeled DNA’s structure. Using Franklin’s work, created a new model in which two strands of nucleotides wound about each other, forming a double helix

Chargaff’s rules state that in any species there is an equal number of A and T bases, and an equal number of G and C bases

DNA (deoxyribonucleic acid) The heritable genetic information of an organism

Write down on your note sheet the importance of Watson and Crick.

What does DNA look like? Double Helix: structure of DNA – 2 strands, twisted into a helical shape Make an analogy for the structure of DNA.

Nucleotides Subunits (monomers) of DNA (polymer) Made up of: Sugar Phosphate group Nitrogenous Base

Nucleotides join together Joined together by covalent bonds that connect sugar of one nucleotide to the phosphate group of the next The repeating pattern of sugar-phosphate is called a sugar-phosphate “backbone”

Base-Pair Rule DNA is made up of 4 nitrogenous bases: Adenine (A), Thymine (T), Guanine (G), Cytosine (C)

The Base Pairing Rule (A) Adenine = (T) Thymine (C) Cytosine = (G) Guanine Bases joined together by hydrogen bonds

Fig. 16-UN1 Purine + purine: too wide Pyrimidine + pyrimidine: too narrow Purine + pyrimidine: width consistent with X-ray data

Fig. 16-8 Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Figure 16.8 Base pairing in DNA Guanine (G) Cytosine (C)

Practice http://www.youtube.com/watch?v=qy8dk5iS1f0 One DNA strand is provided, write the bases of the complimentary strand C G T A G C A T

Activity- Making a Model of DNA Materials: 4 beads of different color 2 long pipe cleaners 8-12 short pieces of pipe cleaner 1 index card 1 DNA sequence