DNA Deoxyribonucleic Acid Purpose DNA codes for proteins and is the blueprint for life. The same DNA is found in all cells in your body (sex cells have.

DNADeoxyribonucleic Acid

Purpose• DNA codes for

proteins and is the blueprint for life.

• The same DNA is found in all cells in your body (sex cells have half of the DNA)!

• Only certain parts of the DNA molecule are read and used in each cell type.

DNA and Chromosomes

• Prokaryotes – DNA in circular form

called “plasmid” – E. Coli has over 4.6

million base pairs!

• Eukaryotes – Linear DNA in form of

chromosome– Human cells contain

about 3 billion base pairs!

Chromosome Composition

• A Nucleosome is DNA tightly wound around protein spheres called “histones”

• Nucleosomes supercoil and become thick fiber of chromosomes

• Nucleosomes play role in gene regulation – turning off and on genes

Structure

• Discovered by Watson and Crick in 1953

• Shaped like a twisted ladder called a “double helix”

Rosalind Franklin

• Used X-Ray diffraction to get information about the structure of DNA:

Chargaff’s rules

• The relative amounts of adenine and thymine are the same in DNA

• The relative amounts of cytosine and guanine are the same.

Nucleotide

• Subunit of DNA

• made up of a sugar, phosphate and one nitrogen base.

What makes up the sides of DNA Ladder?

1. Deoxyribose sugar

2. Phosphate group

• Run in opposite directions called “anti-parallel”

• Important when copying DNA

• Run in direction 5’-3’

Nitrogen bases make up RungsPurines Pyrimidines

(double ring) (single ring)

Adenine-------(double H bond)--------Thymine

Guanine-------(triple H bond)---------Cytosine

Putting it all together

• The order of bases in DNA makes you different from the person sitting next to you!