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Who’s Responsible?

Rosalind Franklin took diffraction x-ray photographs of DNA crystals

In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays

Nobel Peace Prize awarded

DNA-DNA-Deoxyribonucleic Deoxyribonucleic AcidAcidDNA DNA is often called the blueprint of life..

In simple terms, DNA contains the instructions for making

proteins within the cell.

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Why do we study DNA?Why do we study DNA?We study DNA for many reasons, e.g.,

its central importance to all life on Earth,

medical benefits such as cures for diseases and

better food crops. 4

Our genes are on our chromosomes.

Chromosomes are made up of a chemical called DNA.

Chromosomes and DNAChromosomes and DNA

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SHAPE of DNASHAPE of DNA

DOUBLE HELIX-two sided-twisted-ladder

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Nucleotide: 3 components 1)Deoxyribose Sugar

2)Phosphate

3)Nitrogen Base

DNA is made of repeating nucleotides

Nucleotide: monomer

DNA: polymer

DNA Structure

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Cytosine C Thymine T

Adenine A

Guanine GThe amount, the order

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Four nitrogenous basesFour nitrogenous bases

DNA has four different bases:

PyrimidinesPyrimidines are are single ring single ring basesbases..

PurinesPurines are are double ring double ring bases.bases.

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Two Kinds of Bases in DNA

Two Stranded DNATwo Stranded DNASides are called the backbone: made of alternating Phosphate and Sugar

The ladder rungs: made of paired nitrogen bases.

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Hydrogen BondsHydrogen BondsThe Bases connect by Hydrogen Bonds

Hydrogen bonds are weak but there are millions and millions of them in a single molecule of DNA.

The hydrogen bonds between the bases are shown here with dotted lines

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Adenine and Thymine always join together

AA TTCytosine and Guanin always join together

CC GGPyrimidines and Purines always pair together

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DNA by the NumbersDNA by the Numbers

Each cell has about 2 m of DNA.

The average human has 75 trillion cells.

The average human has enough DNA to go from the earth to the sun more than 400 times.

DNA has a diameter of only 0.000000002 m.

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The earth is 150 billion mor 93 million miles from the sun.