The Structure of dnA Big Q: What are the chemical components of DNA? Big Q: What clues helped scientists solve the structure of DNA? Big Q: What does the double helix model tell us about DNA?

Engage - Describe the sculpture What is the structure of DNA and how does it function in genetic inheritance?

Explain - The components of DNA The building blocks of DNA are called nucleotides. Parts of a nucleotide: 1. deoxyribose sugar 2. nitrogenous bases 3. phosphate group There are four types of nitrogenous bases in DNA: Guanine Adenine Thymine Cytosine

Explain - Nitrogenous bases Purine Structure: Pyrimidine Structure: Double rings A purine must bind to a pyrimidine: A - T G - C T - A C - G Single ring

Elaborate - Chargaff’s Rule Erwin Chargaff discovered the ratio of nitrogenous bases in DNA Chargaff’s Rule - the percentage of A will be the same as the percentage of T in a DNA strand. The percentage of C will be the same as the percentage of G in a DNA strand. If 20% of your DNA consists of T, how much A do you have? 20%

Elaborate - Base Percentages Analyze the data on the worksheet using Chargaff’s Rule. ***Answer all questions on your worksheet.

Explore - The history of DNA Structure Rosalind Franklin - British scientist famous for discovering the helix structure of DNA Watson and Crick - discovered all the parts of DNA based on Franklin’s picture Watson + Crick X-Ray Diffraction

Explore - DNA models If a twisted ladder is used as a model of DNA, which parts of the DNA correspond to the sides of the ladder? What parts of the DNA correspond to the rungs of the ladder?

Elaborate - Check for Understanding How is solving the puzzle of DNA’s structure an example of a collection of discoveries by different scientists?

Explain - the double helix model What did these scientists discover about the model? 1. Antiparallel Strands - run in opposite directions 2. Hydrogen Bonding - weak bonds hold DNA together 3. Base Pairing - A and T, G and C

Elaborate - DNA Modeling Students will create their own models of DNA ***Answer all questions in your lab packet