DNA STRUCTURE Unit 4 DNA Facts DNA Deoxyribo
DNA STRUCTURE Unit 4
DNA Facts DNA Deoxyribo. Nucleic Acid � Basis for all living things Foundation for all diversity & unity on Earth � Every living thing has DNA. That means that you have something in common with a zebra, a tree, a mushroom and a beetle!!!! � DNA is too small to see, but under a microscope it looks like a twisted up ladder! �
History of DNA � � � Frederick Griffith Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria. (1928) Oswald Avery Expanded on Giffith’s experiment. (1944) Hershey & Chase Studied bacteriophages (viruses that kill bacteria). Helped determine if genes were made of DNA or proteins. (1952) Rosalind Franklin X-ray photo of DNA. (1952) Watson and Crick described the DNA molecule from Franklin’s Xray. (1953)
Structure of DNA Nucleotide � Small units that link together to form DNA � Made of 3 parts Phosphate Group 5 -C sugar molecule deoxyribose Nitrogen Base
Structure of DNA cntd. � Nitrogen (N) base N base makes nucleotides different 4 bases ▪ Adenine (A) ▪ Guanine (G) ▪ Thymine (T) ▪ Cytosine (C) 2 main groups of bases ▪ Purines ▪ Double ring of C & N atoms ▪ Includes adenine and guanine ▪ Pyrimidines ▪ Single ring of C & N atoms ▪ Includes thymine and cytosine � Base pairing rules Purines bind to pyrimidines Adenine binds to thymine Guanine binds to cytosine
Structure of DNA cntd. Double Helix � Model created by James Watson & Francis Crick � Structure of DNA � “spiral staircase” made of 2 strands of nucleotides twisting around a central axis. � Also known as a “twisted ladder” ▪ ▪ ▪ Sides of ladder are made of alternating sugar and phosphate units held together with a strong covalent bond Rungs are made up of a purine and a pyrimidine held together by a weak Hydrogen (H) bond. Base pairing results in a complementary strand (this is how DNA replicates)
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