(Deoxyribonucleic Acid) (Deoxyribonucleic Acid) DNA (Deoxyribonucleic Acid) (Deoxyribonucleic Acid) History and Structure C10L28C12

Chromosomes are made of DNA Chromosomes and DNA During Mitosis we can see Chromosomes Chromosomes are made of DNA

Chromosomes and DNA

Today’s Goals Item 1 What is DNA? Item 2 DNA History Item 3 DNA Structure Item 4 DNA Nitrogen Bases Item 5 Chargaff's Rule

What is DNA? DNA holds all the genetic information that determines an organism’s traits. Hair Color Height Skin Tone Eye Color

What is DNA? Within the structure of DNA is the information for life—the complete instructions for manufacturing all the proteins for an organism. DNA achieves its control by determining the structure of proteins. Enzymes (a type of protein) control the chemical reactions needed for life. Eating, running, even thinking

Today’s Goals Item 1 What is DNA? Item 2 DNA History

Johann Friedrich Meischer 1869 The first scientist to identify and isolate DNA He called it nuclein

Important clues to the structure of DNA Rosalind Franklin 1952 Studied DNA structure with X-ray diffraction Important clues to the structure of DNA Twisted strands (helix) Angle suggested 2 strands ( double-helix) Nitrogen bases near the center of the molecule

James Watson and Francis Crick 1953 Built a DNA model based on the clues from Franklins X-ray diffraction

Today’s Goals Item 1 What is DNA? Item 2 DNA History Item 3 DNA Structure

DNA is a Double Helix A double helix looks like a twisted ladder.

The Double Helix Building Blocks A DNA strand is a polymer. They are very long! It’s length is what allows DNA to hold so much information The repeating subunits of DNA are called nucleotides

Nucleotide Structure Composed of 3 parts Phosphate Nitrogen Base There are 4 possible bases. Broken down into 2 categories Phosphate Nitrogen Base Deoxyribose Sugar

Nucleotide Structure The phosphate groups and deoxyribose (sugar) molecules bond to form the backbone of the chain The nitrogenous bases stick out like the teeth of a zipper.

Today’s Goals Item 1 What is DNA? Item 2 DNA History Item 3 DNA Structure Item 4 DNA Nitrogen Bases

Types of Nitrogen bases There are two types of nitrogen bases Purines Pyrimidines Pyrimadines have one ring Purines have two rings

Types of Nitrogen bases There are two types of nitrogen bases Purines Pyrimidines

Today’s Goals Item 1 What is DNA? Item 2 DNA History Item 3 DNA Structure Item 4 DNA Nitrogen Bases Item 5 Chargaff's Rule

How the double helix is formed Nitrogen bases bond to one another to connect the two strands But only certain bases can bond to one another

Chargaff’s Rule – Base Pairing 1 Purine must bond to 1 pyrimadine Adenine only bonds to Thymine Guanine only bonds to Cytosine Purines Pyrimidines At The Grand Canyon