Nucleotides & Nucleic Acids. Central Dogma of Biology

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1 Roles: Energy currency (ATP, GTP) Chemical links in response of cells to hormones (camp) Involved in cofactors (NAD, FAD, CoA) Metabolic intermediates (acetyl CoA) Constituents of nucleic acids, DNA and RNA Central Dogma of Biology Storage and transmission of genetic info Contains genes rrna - structural components of ribosomes mrna - carries genetic info from gene to ribosome to make protein trna - adaptor that translates info in mrna into amino acid sequence

2 Nucleotides: 1. Nitrogenous base 2. Pentose sugar 3. Phosphate Nucleotides & Nucleic Acids Nucleosides: 1. Nitrogenous base 2. Pentose sugar Nitrogenous bases are either pyrimidines or purines

3 Nitrogenous bases are either pyrimidines or purines

4 Ribose sugars can be either 2 -deoxy (DNA) or have a 2 -OH (RNA)

5

6 Hydrolysis of RNA Nucleotides & Nucleic Acids

7 Properties of RNA and DNA Forces involved in structure 1.

8 Properties of RNA and DNA Forces involved in structure 1. Hydrophobic Bases hydrophobic at neutral ph, hydrophobic stacking interactions

9 Properties of RNA and DNA Nitrogenous rings are mostly planar Resonance in cyclic rings allow nucleotide bases to absorb UV light

10 Properties of RNA and DNA Forces involved in structure 2. Hydrogen bonding patterns in RNA and DNA Involve ring N, carbonyls, amino groups Permits complementary association of 2 strands of nucleic acid (structure of DNA by Watson & Crick) Uridine (RNA)

11 Discovery of DNA structure and its role in housing genetic information Miescher 1868 Isolate phosphorus-containing substance which he termed nuclein Acidic (DNA) & basic portions (protein) Hypothesize that nuclein associated with genetic inheritance Avery-MacLeod-McCarty 1944 Direct evidence that DNA carries genetic info

12 Discovery of DNA structure and its role in housing genetic information Avery-MacLeod-McCarty 1944 Direct evidence that DNA carries genetic info

13 Discovery of DNA structure and its role in housing genetic information Avery-MacLeod-McCarty 1944 Direct evidence that DNA carries genetic info Griffith Avery-MacLeod-McCarty?? Results Treat DNA with protease - transform Treat DNA with deoxyribonucleasesdestroy transforming activity

14 Nucleotides & Nucleic Acids Hershey-Chase 1952 More evidence that DNA carries genetic info DNA radiolabeled Protein radiolabeled

15 Chargaff s rules 1940s Nucleotides & Nucleic Acids 1. Base composition of DNA varies from one species to another 2. DNA from different tissues of same species have same base composition 3. Base composition of DNA in given species does not change with age, nutritional state, environment 4. In all cellular DNAs, regardless of species, the number of adenosine residues is equal to the number of thymidine residues (A=T), and the number of guanosines = cytidines (G=C) A + G (purines) = C + T (pyrimidines)

16 Watson & Crick 1953 (Franklin & Wilkins too) Franklin & Wilkins Used x-ray crystallography to analyze fibers of DNA Heavy bands - indicates recurring bases X - indicates helical structure

17 Watson & Crick 1953 (Franklin & Wilkins too) Watson & Crick Used x-ray crystallography data Used Chargaff s rules 3D structure of DNA, strands antiparallel

18 DNA structure Complementarity (replicate by separating strands and synthesizing complementary strand for each) Strands not identical in base sequence or composition DNA replication

19 DNA structure - different 3D forms