All nucleotides contain three components: 1. A nitrogen heterocyclic base 2. A pentose sugar 3. A phosphate residue Nucleic Acids DNA and RNA are nucleic acids, long, thread-like polymers made up of a linear array of monomers called nucleotides Ribonucleotides have a 2’-OH Deoxyribonucleotides have a 2’-H Chemical Structure of DNA vs RNA Structure of Nucleotide Bases Bases are classified as Pyrimidines or Purines The nucleus contains the cell’s DNA (genome) RNA is synthesized in the nucleus and exported to the cytoplasm Nucleus Cytoplasm DNA RNA (mRNA) Proteins replication transcription translation dA dG dT dC Deoxyribonucleotides found in DNA Nucleotides are linked by phosphodiester bonds Bases form a specific hydrogen bond pattern DNA is double stranded The strands of DNA are antiparallel The strands are complimentary There are Hydrogen bond forces There are base stacking interactions There are 10 base pairs per turn Properties of a DNA double helix DNA is a Double-Helix RNase P M1 RNA Transcription of a DNA molecule results in a mRNA molecule that is single- stranded. RNA molecules do not have a regular structure like DNA. Structures of RNA molecules are complex and unique. RNA molecules can base pair with complementary DNA or RNA sequences. G pairs with C, A pairs with U, and G pairs with U. bulge internal loop hairpin [...].. .Nucleic Acids in Acid and Base The glycosidic bond of DNA and RNA is hydrolyzed by acids Order of stability: dA, dG < rA, rG < dC, dT < rC, rU dA, dG hydrolyzed in boiling 0.1 M hydrochloric acid in 30 min rA, rG hydrolyzed in boiling 1 M hydrochloric acid in 60 min rC, rU hydrolyzed in boiling 12 M perchloric acid in 60 min DNA is quite stable under basic... 6-4 photoproduct Nucleic Acids Where are they found in nature? and What do they look like? Genomes Source of DNA Size (bases) Type Escherichia coli 9,200,000 Closed-circular double-stranded DNA Bacillus subtilis 4,200,000 Closed-circular double-stranded DNA F plasmid 95,000 Closed-circular double-stranded DNA λ phage 48,500 Linear double-stranded DNA T7 phage 40,000 Linear double-stranded DNA M13 phage... Closed-circular single-stranded DNA MS2 phage 3,600 Linear single-stranded RNA Human 6,000,000,000 Linear double-stranded DNA Fruit fly 270,000,000 Linear double-stranded DNA HIV 9,700 Linear single-stranded RNA DNA molecules are packaged in the cell as structures called chromosomes Bacteria have a single chromosome Eukaryotes have multiple chromosomes A single chromosome contains thousands of genes, each... catalyzed by enzymes Adenine and Cytosine are methylated more often than Guanine and Thymine Methylation is confined to specific regions of DNA and aid in biological processes E coli DNA is methylated to distinguish its DNA from that of foreign invaders In eukaryotic cells about 5% of cytidines are methylated, producing 5-methylcytidine Spontaneous Alterations in Nucleic Acids In a human cell, DNA undergoes... in Nucleic Acids In a human cell, DNA undergoes spontaneous alterations in structure (mutations) As a cell ages, the number of mutations increases, making it likely that a cell’s normal processes may be altered There is a link between spontaneous mutation, aging, and carcinogenesis Depurination Why does DNA contain thymine and not uracil? Hypothesis: If DNA contined uracil, during replication of DNA... has a single double-stranded DNA molecule as its genome There are 4,639,221 base pairs in the E coli genome The DNA is 1.7 mM long, 850 times the length of an E coli cell plasmid Large DNA molecules are compacted in a cell by supercoiling relaxed supercoiled DNA in eukaryotic cells is packaged into nucleosomes, which contain proteins called histones DNA wrapped around a histone core (side view) Nucleosomes... scaffolds In eukaryotes, genes contain exons (coding regions) and introns (non-coding regions) Prokaryotic genes do not contain introns Telomeres Telomeres are sequences at the end of eukaryotic chromosomes that help stabilize the chromosome Telomeres are repeats of the following sequence: 5’-(TxGy)n 3’-(AxCy)n x and y = 1 to 4 The TG strand is longer 5’-TTTGGTTTGGTTTGGTTTGGTTTGGTTTGG… 3’-AAACCAAACCAAACC…... 5’-TTTGGTTTGGTTTGGTTTGGTTTGGTTTGG… 3’-AAACCAAACCAAACC… Can be >10,000 nucleotides in mammals The ends of the chromosome are replicated by the enzyme telomerase Telomeres and aging There appears to be a relationship between the length of telomeres at the end of chromosomes and the age of an individual The older you are, the shorter your telomeres are Germ-line cells (reproductive cells) contain telomerase activity Non-germ-line... telomerase activity We have a certain length of telomeres that we are born with As we age, the telomeres get shorter Is our life-span pre-determined by the length of our telomeres? Internet Resources Nucleic Acids National Center for Biotechnology Information (NCBI) National Library of Medicine (NLM) National Institutes of Health (NIH) http://www.ncbi.nlm.nih.gov/ ... contined uracil, during replication of DNA the uracils would be base-paired with adenine Deaminated cytosines would also be base-paired with adenine This would decrease the number of G-C base pairs over time and increase the number of A-U base pairs Eventually all the G-C base pairs could be lost The genetic code would not exist as we know it Ultraviolet light is damaging to DNA Near-UV radiation (wavelengths