The Structure of DNA Why do we care about DNA?

Nucleic Acid It’s all in the name Nucleotides DNA stands for DeoxyriboNucleic Acid so it should come as no surprise that DNA is a… Nucleic Acid What subunits make up nucleic acids? Nucleotides

The Structure of a Nucleotide The basic building block of DNA is the structure called a nucleotide. Nucleotides are made up of three parts. Nitrogenous Base Phosphate Sugar

The Four Bases Adenine Thymine Cytosine Guanine In DNA there are four different types of nucleotide. Different nucleotides have different bases. Adenine Thymine Cytosine Guanine

The Four Nucleotides Purines Two Rings Pyrimidines One Ring

DNA is made up of two strands Each strand of DNA is held together by a sugar-phosphate backbone. The phosphate of each nucleotide in a strand is attached to the sugar of the nucleotide next to it.

The Double Helix The two strands of DNA are attached at the nitrogenous bases. The base-pairing rule states that Adenine always pairs with Thymine and Cytosine always pairs with Guanine. A T C G

The Double Helix

The Double Helix

The Double Helix The two strands of DNA are twisted around each other to form a double spiral or double helix.

The Double Helix The double stranded DNA makes one complete twist for every 10 pairs of bases. The two strands are pointed in opposite directions

DNA Model You will build a model of DNA It must hang from the ceiling or stand on its own. The following parts must be included: deoxyribose sugar, phosphate group, adenine, thymine, guanine, cytosine, covalent bonds and hydrogen bonds. No perishable materials and no kits

DNA Model The DNA must be twisted and must be at least 10 base pairs long, making a complete twist. A key must be included or the parts must be clearly labeled. You may work with one other person, but you must inform me by Friday Feb 19th The project is worth 30 points and is due on Tuesday March 1st.

DNA Grading Sugars labeled - 4 points _____ Phosphate labeled - 4 points _____ Bases labeled - 4 points_____ Covalent bonds - 2 points_____ Hydrogen bonds - 2 points _____ Directional strands – 2 points ____ Complete twist - 2 points _____ Correct structure - 5 points _____ Creativity - 5 points _____