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Topic 18 Intro to DNA and RNA.docx

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Biochemistry 2280A
Derek Mc Lachlin

Topic 18: Introduction to DNA and RNA Explain the chemical structure of nucleic acid polymers, without memorizing the structures of the nitrogenous bases Describe B-DNA and the higher order structures formed by RNA, and the important forces that stabilize these structures Identify chemical and structural similarities and differences between DNA and RNA  Major functions of DNA and RNA DNA RNA  Carries genetic material  Template for producing proteins  Important to make an (mRNA) (DNA gets transcribed offspring to this)  Makes up much of ribosome (rRNA)  Carries amino acids to ribosome (tRNA)  Also involved in splicing  90% of your genome is transcribed into RNA a lot of it are little RNAs with regulatory functions  Building blocks of RNA = ribonucleotides  Composed of three parts  a sugar, a nitrogenous base, and a phosphate  Sugar=ribose  Sugar + base = nucleoside  Forms a N-glycosidic bond because a nitrogen is involved vs. an oxygen  Sugar is always in B configuration in this bond (cannot switch back and forth anymore once in a bond)  Use numbers to describe the nitrogenous bases (plain numbers)  To number the sugar we put a prime to distinguish those atoms from the ones in the base  Base is always on the 1’ carbon  Add a phosphate group on the highest number carbon  When you add a phosphate to it becomes a nucleotide  Sugar + base + phosphate= nucleotide  Two phosphate= diphosphate, three phosphates= triphosphate  ATP is one of the building blocks/ bases that goes into RNA ! (adenosine triphosphate) !  Different for DNA is that sugar is deoxyribose instead of ribose  Called a deoxyribonucleotide Building blocks of DNA NH2 triphosphate N cytosine BuilOingblOcksofORNA N O –O P O P O P NOCH 2 O O– O– O4 5 3NH H H cytosiHe deoxycytidine6 2 triphosphate, a1 cytidine, a 5' N OHO H nucleosideeoxHOCH2eoOide 2'-deoxyribose 4' 1' H H N-glycosidic H 3' 2' H bond OH OH ribose  Nitrogenous Bases Purines (six membered ring) Pyrimidines (six membered ring) Base Nucleoside Structure Base Nucleoside Structure Adenine Adenosine Cytosine (C) Cytidine (A) Guanine Guanosine Thymine (T) Thymidine (G) *found in DNA Uracil (U) Uridine (has an H where Thymine has CH )3 *found in RNA relatively flat structures and also kind of hydrophobic have these hydrogen bonding groups on them (hydrophilic) but on the surface there are these pi electrons that are not good for making hydrogen bonds cloud of pi electrons hovering above and below the plane of the ring pyramidines are joined by the nitrogen at the bottom  Polynucleotides  Nucleotides strung together  Sugars are joined to each other via phosphodiester linkages between C3’ and C5’  5’ carbon is joined to 3’ carbon of next deoxyribose  sugar-phosphate backbone phosphodiester linkage  The ends are not the same (polarity=two end are not the same)  have a 5’ end and a 3’ end  There might not be a phosphate group on the 5’ end (phosphate could be on 3’ end) not defining feature  The 5’ end of the polynucleotide strand is where the 5’ carbon is not attached to another monosaccharide  The 3’ end is where the 3’ carbon is not attached to another monosaccharide  (no OH on the 2’ carbon = giveaway that its DNA)  small d stands for deoxy if you ever see that  DNA  when you get to long enough length there’s essentially an infinite diversity of unique molecules possible  Direction convention  By convention, sequences are written 5’ to 3’  For example, in the sequence GA
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