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DNA History and DNA Structure. How did we get here?? – Make a table using pages 204-212. DNA structure. Purines have two rings Pyrimidines have one ring. DNA has four kinds of bases, A, T, C, and G. Thymine (T). Cytosine (C). Adenine (A). Guanine (G). Pyrimidines. Purines.
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DNA structure Purines have two rings Pyrimidines have one ring
DNA has four kinds of bases, A, T, C, and G Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Pyrimidines Purines Figure 10.2B
DNA is a double-stranded helix • James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin Figure 10.3A, B
DNA and RNA are polymers of nucleotides • DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Nitrogenous base(A, G, C, or T) Sugar Phosphategroup Nucleotide Thymine (T) Sugar(deoxyribose) DNA nucleotide Figure 10.2A Polynucleotide Sugar-phosphate backbone
Hydrogen bonds between bases hold the strands together: A and T, C and G Hydrogen bond Ribbon model Partial chemical structure Computer model Figure 10.3D
Each strand of the double helix is oriented in the opposite direction 5 end 3 end P P P P P P P P 3 end 5 end Figure 10.5B
DNA structure Figure 2.5 - 5’ end : Phosphate at carbon 5 is not bound to another nucleotide 3’ end – carbon at position 3 is not joined to another nucleotide.
DNA structure What is the complementary sequence to the following ? 5’ – ATG – 3’ Draw the complementary sequence. Include all the correct drawing of molecules, and the bonding between them. Consult your text book for help. Read pages 215-218.
DNA structure Packing of information 2 m of material in 4 uM DNA associates with a family of proteins called histones Histones form structures called nucleosomes Condense further to ultimately form chromatin – Long intertwined strands of DNA. During cell division threads of chromatin condense and become visible as distinct chromosomes
DNA structure DNA super coiling: the formation of additional coils in the structure of DNA due to twisting forces on the molecules
What is a chromatid? What is a centromere? What is a chromomere? Chromatid - one of the two copies of DNA making up a duplicated chromosome, which are joined at their centromeres. Centromere – a protein structure that links sister chromatids Chromomere - serially aligned beads or granules of eukaryotic chromosome resulting from local coiling.
