Milestones of the Last Century Going to the moon Computer technology Communications technology     Solving the structure of DNA and unraveling the mysteries of heredity

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DNA Carries the Code of Life How is genetic information (DNA) copied every time a cell divides? How is genetic information stored in DNA?

DNA Carries the Code of Life In 1953, Watson and Crick discovered the structure of DNA DNA is composed of a double helix

The Structure of DNA S = sugar P = phosphate B = base (A, G, C, T) - S - P - S - P - S - P - S - P - S - P - S - B B B B B B B B B B B B

DNA Contains Four Bases: A = Adenine G = Guanine T = Thymine C = Cytosine

DNA Base Pairing Rules: A always pairs with T G always pairs with C

The Structure of DNA S = sugar P = phosphate B = base (A, G, C, T) - S - P - S - P - S - P - S - P - S - P - S - G C A T A T T A T A C G

A G G C T A T C C A A G T A G G A T T C T C C G A T A G G T T C A T C C T A A G A G G C T A T T C C G A T A C C A A G T A G G A T T C A G T A G G A T T C T C A T C C T A A G G G T T C A T C C T A A G DNA Replication

A G G C T A T C C A A G T A G G A T T C T C C G A T A G G T T C A T C C T A A G A G G C T A T T C C G A T A C C A A G T A G G A T T C A G T A G G A T T C T C A T C C T A A G G G T T C A T C C T A A G DNA Replication A G G C T A T C C A A G T A G G A T T C T C C G A T A G G T T C A T C C T A A G A G G C T A T C C A A G T A G G A T T C T C C G A T A G G T T C A T C C T A A G

How is genetic information copied every time a cell divides? The two strands separate and each strand is used as a template for the synthesis of a new strand.

How is genetic information stored in DNA? As a sequence of bases (AGGCATTCGCAATT…)

the players…... James Watson and Francis Crick -solved the DNA structure -awarded the Nobel prize

the players…... Linus Pauling -winner of two previous Nobel prizes -was “hot on the trail” to solving the DNA structure, but lacked critical data

the players…... Rosalind Franklin - X-ray crystallography expert who generated key data for solving the structure of DNA

the players…... Erwin Chargaff - figured out the ratio of A = T and G = C - didn’t realize that this meant DNA was double stranded

The “Gurdon” experiment: Does every cell in an organism contain all the genetic information to make a complete individual?

Unfertilized egg Ultraviolet radiation of egg to destroy nucleus Enucleated egg Host egg

Donor nucleus

Host eggDonor nucleus