Getting Organized How genetic material is arranged

DNA (Deoxyribonucleic Acid)

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)

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

Chargaff’s Rule Adenine Thymine Adenine must pair with Thymine GuanineCytosine Guanine must pair with Cytosine about the same Their amounts in a given DNA molecule will be about the same. G C TA

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…

DNA Replication Semiconservative Model: Semiconservative Model: Watson and Crick showed: 1.Watson and Crick showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.. Parental DNA DNA Template New DNA

Organization in the Nucleus Long strands of chromatin condense into chromosomes. The sister chromatids are the result of replication. Each chromatid has the same base sequence (information) Histone proteins act as spools