August 7, 2015 Bell Work: True or False: All living organisms have DNA. Objective: The student will be able to… Explain his or her knowledge of DNA. Define DNA

Today in History 1912 The Progressive Party nominated Theodore Roosevelt for president. 1971 Apollo 15 returned to Earth after a manned mission to the moon.

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What do you know about DNA?

DNA By the 1950s most scientists were convinced that genes were composed of DNA DNA: Deoxyribonucleic Acid

Watson and Crick James Watson and Francis Crick were researchers at Cambridge University They were the first to piece together a model of the structure of DNA The discovery of the structure of DNA was important because it clarified how DNA could serve as the genetic material.

Watson and Crick Watson and Crick determined the DNA was a double helix Two strands twisted around each other Similar to a winding staircase

DNA Double-Helix

DNA Structure Worksheet

DNA Structure Each helix is made of linked nucleotides Each nucleotide is composed of three groups A phosphate group A five carbon sugar molecule A nitrogen containing base

DNA Structure The five carbon sugar is known as deoxyribose The sugar molecule and the phosphate group are the same for each nucleotide in a molecule of DNA There are four different nitrogen bases Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

DNA Structure Purines: nitrogen bases made up of two rings of carbon and nitrogen atoms Adenine Guanine Pyrimidines: nitrogen bases made up of a single ring of carbon and nitrogen atoms Thymine Cytosine

DNA Structure Base pairing rules: A purine always pairs with a pyrimidine Adenine pairs with Thymine Guanine pairs with Cytosine

Nucleotide Base Pairing

DNA Structure Adenine forms two hydrogen bonds with Thymine Cytosine forms three hydrogen bonds with Guanine The hydrogen bonds keep the two strands of DNA together

ATACGACCGTTAC TATGCTGGCAATG DNA Structure Strictness of base pairing rules results in two strands that form complementary base pairs The sequence on one strand determines the sequence on the other strand ATACGACCGTTAC TATGCTGGCAATG

DNA Structure Worksheet

Ticket Out Finish each of these sentences: DNA looks like _____. I've heard of DNA in _______. The function of DNA is _______. DNA is used in society for _______. DNA is made of ________. I don't think DNA analysis should be used for _______.