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Unformatted text preview: 0B X X X X X X I I I V V V . . . D D D N N N A A A 1B E E E v v v i i i d d d e e e n n n c c c e e e f f f o o o r r r D D D N N N A A A a a a s s s a a a G G G e e e n n n e e e t t t i i i c c c M M M a a a t t t e e e r r r i i i a a a l l l Somatic cells (normal cells of the body tissues) contain twice as much DNA as do reproductive cells. DNA has the same nitrogenous base composition in all individuals of the same species of organisms, but different species have different base compositions. Fig. 16-3 Bacterial cell Phage head Tail sheath Tail fiber DNA 100 nm DNA transfers genetic information during bacterial growth (Griffith, 1920s, and Avery 1940s). Phages (viruses of bacteria), when infecting the host, transfer only DNA; the phage protein stays outside the infected cell (Hershey & Chase, 1950s). Fig. 16-4-3 EXPERIMENT Phage DNA Bacterial cell Radioactive protein Radioactive DNA Batch 1: radioactive sulfur ( 35 S) Batch 2: radioactive phosphorus ( 32 P) Empty protein shell Phage DNA Centrifuge Centrifuge Pellet Pellet (bacterial cells and contents) Radioactivity (phage protein) in liquid Radioactivity (phage DNA) in pellet 2B M M M o o o l l l e e e c c c u u u l l l a a a r r r S S S t t t r r r u u u c c c t t t u u u r r r e e e Nucleic acids are polymers of nucleotides. Fig. 16-1 Fig. 16-6 (a) Rosalind Franklin (b) Franklins X-ray diffraction photograph of DNA 5B N N N u u u c c c l l l e e e o o o t t t i i i d d d e e e s s s Nucleotides consist of nitrogenous bases joined, at its first carbon, to a pentose sugar, which is phosphorylated at carbon 5. Nitrogenous bases come in 5 flavors: single ring pyrimidines: Thymine (T), Cytosine (C), Uracil (U) double ring purines: Guanine (G), Adenine (A) 6B S S S u u u g g g a a a r r r--- p p p h h h o o o s s s p p p h h h a a a t t t e e e b b b a a a c c c k k k b b b o o o n n n e e e Neighboring nucleotides are joined by a phosphate ester linkage between the 5' carbon of ribose and the 3' of the next ribose....
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