Ch.6s.1 Genetics: History and Structure of DNA First Last Date Period # Chromosome DeoxyriboNucleic Acid Since chromosomes contain both protein and DNA, scientists did not know which one contained the instructions, the gene. The gene must do two things: have instructions for cell processes and for building cell structures, and must be copied each time a cell divides DeoxyriboNucleic Acid (DNA) was thought to be a simple molecule, so most scientists thought genes were made of protein

Ch.6s.1 Genetics: History and Structure of DNA First Last Date Period # nucleotide Sugar Phosphate Nucleotide base (A, T, C, G) Chargaff’s rule A unit of DNA is a strand composed of subunits called nucleotides. Each DNA nucleotide is composed of a sugar (deoxyyribose), phosphate, and nucleotide base. <<<draw picture>>> Chargaff found that the amount of T=A and G=C in a sample of DNA

Ch.6s.1 Genetics: History and Structure of DNA First Last Date Period # Maurice Wilkins Rosalind Franklin Watson Double helix Nobel Prize Maurice Wilkins and his student, Rosalind Franklin, used X-ray diffraction to determine DNA has a spiral shape. James Watson and Francis Crick examined Franklin’s work and determined that DNA is a double helix of sugar and phosphate connected by pairs of bases Crick, Watson & Wilkins shared Nobel Prize in 1963

Ch.6s.1 Genetics: History and Structure of DNA First Last Date Period # Double helix Twisted ladder Adenine (A) Thymine (T) Guanine (G) Cytosine (C) Base-pairing rules On the double helix, or twisted ladder, the rails of the ladder are made from alternating sugar and phosphate; the rungs of the ladder are made from nucleotide base-pairs. <<<draw picture>>> The nucleotide bases on DNA are adenine (A), thymine (T), guanine (G), and cytosine (C). They always bond according to the base-pairing rules: A-T and G-C. <<<draw picture>>>

Ch.6s.1 Genetics: History and Structure of DNA First Last Date Period # complementary X: AGTCGAC TCAGCTG Replicate template A is complementary to T and G is complementary to C, so the sequence of bases on one entire strand of DNA is always complementary to the sequence of bases on the entire other strand A replicate of one strand is made by separating the two strands, and attaching complementary nucleotides to each strand Each OLD strand is a template to build each NEW strand on Each replicate has one OLD template and one NEW strand