DNA The Blueprint of life

DNA  DNA stands for deoxyribonucleic acid and is the hereditary material in humans almost all other organisms  99.9% of human DNA is exactly the same, only.1% gives each individual their own personal fingerprint. This means that only.1% codes for proteins that express our differences

DNA  There is a copy of our entire DNA sequence in almost every cell of our body, with the exception of red blood cells  If unwound and tied together, the strands of DNA in one cell would stretch almost 6 feet, but would be only 50 trillionths of an inch wide  If you could unwrap all of the DNA you have in all of your cells, you could reach the moon and back 6000 times

Rosalind Franklin  Used x-ray crystallography to produce clearest images of DNA ever at that time  Determined that DNA’s structure depended on an external backbone with bases inside  Location of the phosphate sugar

Watson and Crick  Took Frankinlin’s findings and Chagraff’s Rule to discover the shape of DNA was a double helix

DNA  Is made of chemical building blocks (monomers) called nucleotides  These nucleotides are made of a 5- carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base  To form a strand of DNA, nucleotides are linked into chains, with alternating phosphate and sugar groups (the backbone)

Nitrogen Bases  There are four types of nitrogen bases that form the “ladder rungs” of the DNA  Adenine  Thymine  Guanine  Cytosine

Nitrogen Bases  The order, or sequence, of these bases determines what biological instructions are contained in a strand of DNA  For example, the sequence ATCGTT might instruct for blue eyes, while ATCGCT might instruct for brown

Chagraff’s Rule  Purines (2 rings) can only bond with a Pyrimidine (1 ring)  Adenine ALWAYS bonds with thymine  Guanine ALWAYS bonds with cytosine

DNA  The shape of DNA is referred to as a double helix  The “packaged” form of the DNA is called a chromosome  A chromosome consists of DNA tightly wrapped around proteins which when packed together forms a substance called chromatin  Chromosomes are found in pairs called sister chromotids and they are often depicted in an “x” shape

DNA  Tinier than a grain of salt, each human chromosome contains millions of letter of DNA. Each chromosome is like a chapter of a book – brought together, they make up an organism’s entire genome and tell a full genetic story.