DNA Notes
Name: Notes Key
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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Appearance:
o Twisted ______ladder________
o ___Double_____ helix
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Made of:
o Sugar and _phosphate_ backbone (sides of the ladder)
o _Nitrogen Bases_ (rungs of ladder)
 Adenine
 Thymine
 Cytosine
 Guanine
Base pairing:
o ___A__ always with __T___
o __C___ always with __G___
-
o
-
A
T
T
A
T
A
C
G
G
C
G
C
G
C
C
G
A
T
T
A
Nucleotide – a subunit of DNA consisting of a sugar, phosphate, and one of the four
nitrogen bases.
o All living things have the same _4_ 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
-
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
-
__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