Milestones of theLast 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 Crickdiscovered the structure ofDNA

DNA is composed of a double helix

The Structure of DNA

S = sugarP = phosphateB = base (A, G, C, T)

- S - P - S - P - S - P - S - P - S - P - S -

- S - P - S - P - S - P - S - P - S - P - S -

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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 = sugarP = phosphateB = base (A, G, C, T)

- S - P - S - P - S - P - S - P - S - P - S -

- S - P - S - P - S - P - S - P - S - P - S -

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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 TT 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 andeach strand is used as atemplate 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 organismcontain all the genetic informationto make a complete individual?

Unfertilizedegg

Ultravioletradiationof egg todestroynucleus

Enucleatedegg

Host egg

Host egg Donor nucleus

Host egg Donor nucleus