DNA (Deoxyribonucleic Acid). Genetic material of cells… GENES – DNA coded instruction for making...

DNA(Deoxyribonucleic Acid)

Genetic material of cells…Genetic material of cells…

• GENES – DNA coded instruction for – DNA coded instruction for making making PROTEINSPROTEINS

• DNA and RNA are Called DNA and RNA are Called NUCLEIC NUCLEIC ACIDSACIDS

• DNA is made up of repeating molecules DNA is made up of repeating molecules called called NUCLEOTIDES.NUCLEOTIDES.

DNA NucleotideDNA Nucleotide

OO=P-O O

PhosphatePhosphate GroupGroup

N

Nitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

Watson & Crick proposed…Watson & Crick proposed…

•DNA has pairing between nitrogen DNA has pairing between nitrogen bases:bases:

ADENINEADENINE – – THYMINETHYMINE

CYTOSINECYTOSINE – – GUANINEGUANINE

•DNA is made of DNA is made of 22 long strands of long strands of nucleotides nucleotides

DNA Double HelixDNA Double Helix

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladderRungs of ladder””

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

DNA Double HelixDNA Double Helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

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Nitrogenous BasesNitrogenous Bases

• PURINESPURINES

1. Adenine (A)Adenine (A)

2. Guanine (G)Guanine (G)

• PYRIMIDINESPYRIMIDINES

3. Thymine (T)Thymine (T)

4. Cytosine (C)Cytosine (C)T or C

A or G

• AdenineAdenine must pair with ThymineThymine

• GuanineGuanine must pair with CytosineCytosine

• Their amounts in a given DNA molecule will be about the sameabout the same.

G CT A

BASE-PAIRINGSBASE-PAIRINGS

CG

Hydrogen-bonds

T A

Genetic Diversity…Genetic Diversity…• Different arrangements of Different arrangements of

NUCLEOTIDESNUCLEOTIDES in DNA provide in DNA provide DIVERSITYDIVERSITY among living among living organisms.organisms.

The Code of Life…The Code of Life…

• The “code” of the chromosome is the The “code” of the chromosome is the SPECIFIC ORDERSPECIFIC ORDER that nitrogen bases that nitrogen bases occur.occur.

A T C G T A T G C G G…A T C G T A T G C G G…

DNA is wrapped tightly around histones to form a structure called

chromatin.

Chromatin is coiled into Chromosomes