DNA Structure & Replication

History of DNA Structure Erwin Chargaff - 1950 Rosalind Franklin - 1952 James Watson and Francis Crick - 1953

DNA Timeline

DNA To understand genetics, biologists/chemists had to learn the chemical makeup of “the gene”. This chemical makeup is called Deoxyribonucleic Acid or DNA

Units of Structure Scientist began studying DNA structure to find out how it carries information, decides traits, and replicates itself. DNA is a long molecule made up of units called nucleotides. Each nucleotide is make up of a… 5-carbon sugar Phosphate group Nitrogenous base

Things to remember…Nucleic Acids DNA versus RNA

DNA versus RNA: structure

DNA versus RNA: function

DNA - Double Helix A double helix is like a twisted ladder. Sugar and phosphates make up the two sides of the ladder. Nitrogenous bases make up the rungs of the ladder. Hydrogen bonds between the bases hold the two strands together.

Nucleic Acids: Nitrogenous Bases

Nucleic Acids: Base Pairing (DNA)

Nucleic Acids: Base Pairing (RNA)

DNA Strands complement each other. PRACTICE TIME

Which direction do I go? Where’s my head? Where’s my butt?

DNA Strands are Antiparallel.

Counting Carbons

Lagging Strand Leading Strand

Loose DNA to Chromosomes Prokaryotic cells have one large circular piece of DNA in their cytoplasm and several small loops…(why not stored in a nucleus?). Eukaryotic cells have lots of DNA strands (chromatin) that can form of chromosomes and are stored in their nuclei.

Chromatin = Bowl full of Spaghetti

How a Chromosome forms. Chromosome formation step by step: 1. 2. 3. 4. 5. 6.