Genetic material of cells… GENES – units of genetic material that CODES FOR A SPECIFIC TRAITGENES – units of genetic material that CODES FOR A SPECIFIC TRAIT Genes are made up of DNA (deoxyribonucleic acid) & RNA (ribonucleic acid) called NUCLEIC ACIDSGenes are made up of DNA (deoxyribonucleic acid) & RNA (ribonucleic acid) called NUCLEIC ACIDS DNA is made up of repeating molecules called NUCLEOTIDESDNA 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)

A HISTORY OF DNA DNA double helixDiscovery of the DNA double helix A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (all organisms, even bacteria, have DNA) (1928) B.Rosalind Franklin - X-ray photo of DNA. (1952) C.Watson and Crick – Crated a 3D model of the DNA molecule from Franklin’s X-ray. The model was in the form of a double helix.(1953) SEE p

Watson & Crick proposed… DNA had specific pairing between the nitrogen bases:DNA had specific pairing between the nitrogen bases: ADENINE – THYMINE CYTOSINE – GUANINE DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”DNA was made of 2 long stands of nucleotides arranged in a specific way called the “Complementary Rule”

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

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

Chargaff’s Rule Hydrogen bonds can only form between certain pairsHydrogen bonds can only form between certain pairs 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 H-bonds T A

Genetic Diversity… Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.Different arrangements of NUCLEOTIDES in a nucleic acid (DNA) provides the key to DIVERSITY among living organisms.

The Code of Life… The “code” of the chromosome is the SPECIFIC ORDER that bases occur.The “code” of the chromosome is the SPECIFIC ORDER that bases occur. A T C G T A T G C G G…