What is DNA?
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Definition: deoxyribonucleic acid, hereditary material that controls all of the activities of a cell.
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Shape: o ___Double_____ helix
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Made of: o Deoxyribose Sugar and _phosphate_ backbone (sides of the ladder) o _Nitrogen Bases_ (rungs of ladder)
 Adenine
 Thymine
 Cytosine
 Guanine
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Base pairing: o ___A__ always with __T___ o __C___ always with __G___
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Nucleotide – a subunit of DNA consisting of a sugar, phosphate, and one of the four nitrogen
bases. o
All living things have the same base pairs, but the order matters!
DNA History
__Erwin Chargoff__ - 1950 Austrian biochemist that created the base pair rule (Chargaff’s Rules) that state the amount of adenine in DNA always equals the amount of thymine and the amount of guanine in
DNA always equals the amount of cytosine
__Rosaline Franklin____ - 1951 British scientist that used x-ray crystallography to take pictures of
DNA that suggested the molecule had a spiral shape
__James Watson_ (American) and _Francis Crick_ (British) - 1953-54 scientists that used models to discover the shape of the DNA molecule

Making Copies of DNA
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DNA’s structure allows for easy replication
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The double helix _untwists_ and separates
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Each side is used as a template to create
_2_ DNA molecules (each is half old and half new)
Genes and Proteins
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_gene_ - a section of DNA that contains instructions for a trait
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Genes tell the _ribosome_ which proteins to make which determines which traits you have
Changes in Genes
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__mutation_ - change in DNA sequence
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__mutagens_ - cause mutations. Examples include x-rays, UV light, chemicals in cigarettes
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Types of Mutations o Substitution – a base is _switched__ in the sequence o
Deletion – a base is __removed__ from the sequence o
Insertion – a base is __added_ to the sequence o
Genetic Engineering is the transfer of genes from one organism to another. This transfer of genes from one organism to another is usually intended to make new, improved plants and animals, or to fight diseases using gene therapies. Examples: making plants that are resistant to parasites, corn that grows bigger to provide more food, using harmless viruses to introduce helpful genes to patients suffering from genetic disorders. Some scientists argue that genetic engineering may cause unknown health risks or could cause organisms to become genetically weak and prone to disease or disorders.