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1

DO NOW:

What is a Gene?

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OBJECTIVESOBJECTIVES

DEFINE DNA.NAME the scientists who discovered the

structure of a DNA molecule.

DESCRIBE the role of DNA in organisms.NAME the three arts of a Nucleotide.NAME the ! Nitrogenous Bases of DNA."IS# the $ase%airing rules.

DESCRIBE the shae of DNA.

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*DNA stands for deoxyribonucleic acid

--This chemical substance is present in the nucleusOf ALL cells in ALL livin oranisms!

--DNA controls:

1! All of the chemical changes "hich ta#e place in cells!

$! The kind of cell "hich is formed% &muscle%

 blood% nerve% etc'(!)! The kind of organism "hich is produced

&iraffe% bacteria% human% funi% etc'(!

$

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WHO DISCOVERED DNA’sWHO DISCOVERED DNA’s

MOLECULAR STRUCTURE?MOLECULAR STRUCTURE?

&ames 'atson and Francis Cric( werecredited with the discover).

#he) were aided $) information sharedfrom Maurice 'il(ins and RosalindFran(lin.

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*DNA  is a ver* lare molecule made up of a lon

chain of sub-units!

--The sub-units are called nucleotides.

--+ach nucleotide is made up of:

1! a ,-carbon deoxyribose suar 

$! a phosphate roup -PO4

)! ON+ of four Nitrogenous bases

)

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-ibose is a suar% li#e lucose% but "ith onl* five

carbon atoms in its molecule

-Deoxyribose is almost the same but lac#s one

o*en atom

--.oth molecules are represented b* the s*mbol:

/

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--DNA has / t*pes of nitroen bases:

Adenine &A(

Th*mine &T(

0*tosine &0(

Guanine &G(

,

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--The deo*ribose suar% the phosphate% and one

nitroen base combine to form a nucleotide!

adenine

deo*ribose

O/

2

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A molecule of

DNA is formed

 b* millions of

nucleotides 3oined toether

in a lon chain

O/

O/

O/

O/

suar-phosphate

 bac#bone

4 bases

5

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--The DNA consists of a double strand of

nucleotides

--The suar-phosphate chains are on the outside

--The t"o strands are held together b* "ea#

hydrogen bonds bet"een the bases!

6

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O/

O/

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O/

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O/

2-stranded DNA2-stranded DNA 7

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&The bases al"a*s pair up in the same "a*(

Adenine forms a bond "ith Th*mine

and 0*tosine bonds "ith Guanine

18

 Adenine Thymine

Cytosine   Guanine

.A9+-A;NG ;

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O/

O/

O/

thymine

O/

O/

O/

O/

adenine

cytosine

O/

guanine

11

1$

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O/

O/

O/

O/

O/

O/

O/

O/

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O/

1$

1)

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The paired strands are coiled into a spiral called

A DO!"#$ %$#&'

1)

1/

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sugar-phosphate

chain

bases

THE DOUBLETHE DOUBLE

HELIXHELIX

1/

1,

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A DIY model of A DIY model of 

part of a DNApart of a DNA

moleculemolecule

1,