Structure of DNA

What is DNA? Deoxyribo- Nucleic Acid Stores hereditary information It’s stored in the nucleus A segment of DNA is called a gene DNA controls all of the activities of the cell Every cell contains a complete copy of DNA Prokaryotic cells-DNA is in the cytoplasm Eukaryotic cells-DNA is contained In nucleus

DNA is Made of Nucleotides DNA is a string of nucleotides. What is a nucleotide? a sugar, a phosphate, and a nitrogenous base 1940-50’s leading scientists thought DNA just a bunch of simple nucleotides

4 different nitrogen bases= 4 different nucleotides Purines Pyrimidines Adenine Thymine Cytosine Guanine A T G C 2 rings of carbon 1 ring of carbon

4 Bases Always Pair the Same Way Base Pairing Rules: Adenine-Thymine Guanine-Cytosine

Anti-Parallel Strands Strands run in opposite directions.

The Double Helix Model DNA resembles a twisted “ladder” or “double helix” “Rails” or sides are made up of a sugar-phosphate backbone “Rungs” or steps are made up of nitrogenous bases Rungs or Steps Rails or Sides Rails or Sides

Nucleotide: one sugar, one phosphate, one nitrogen base. REVIEW: Nucleotide: one sugar, one phosphate, one nitrogen base. 4 Bases: Adenine Guanine Cytosine Thymine Base Pairing Rules: Adenine = Thymine Guanine = Cytosine Nucleotide Bases 3’ 5’ sugar & phosphate backbone 3’ 5’ Go back to first slide and review Anti-Parallel Strands