DNA (Deoxyribonucleic Acid)

Genetic material of cells… GENES – DNA coded instruction for making PROTEINSGENES – DNA coded instruction for making PROTEINSGENES DNA and RNA are Called NUCLEIC ACIDSDNA and RNA are Called NUCLEIC ACIDS DNA is made up of repeating molecules called NUCLEOTIDES.DNA is made up of repeating molecules called NUCLEOTIDES.

DNA Nucleotide O O=P-O OPhosphate Group Group N Nitrogenous base (A, G, C, or T) (A, G, C, or T) CH2 O C1C1 C4C4 C3C3 C2C2 5 Sugar Sugar(deoxyribose)

Watson & Crick proposed… DNA has pairing between nitrogen bases:DNA has pairing between nitrogen bases: ADENINE – THYMINE CYTOSINE – GUANINE DNA is made of 2 long strands of nucleotidesDNA is made of 2 long strands of nucleotides

DNA Double Helix Nitrogenous Base (A,T,G or C) “Rungs of ladder ” “Legs of ladder” Phosphate & Sugar Backbone

DNA Double Helix P P P O O O P P P O O O G C TA

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Nitrogenous Bases PURINESPURINES Adenine (A) 1.Adenine (A) Guanine (G) 2.Guanine (G) PYRIMIDINESPYRIMIDINES Thymine (T) 3.Thymine (T) Cytosine (C) 4.Cytosine (C) T or C A or G

Adenine ThymineAdenine must pair with Thymine GuanineCytosineGuanine must pair with Cytosine about the sameTheir amounts in a given DNA molecule will be about the same. G C TA

BASE-PAIRINGS CG Hydrogen-bonds T A

Genetic Diversity… Different arrangements of NUCLEOTIDES in DNA provide DIVERSITY among living organisms.Different arrangements of NUCLEOTIDES in DNA provide DIVERSITY among living organisms.

The Code of Life… The “code” of the chromosome is the SPECIFIC ORDER that nitrogen bases occur.The “code” of the chromosome is the SPECIFIC ORDER that nitrogen bases occur. 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