Nucleic Acids The nucleic acids DNA and RNA consist of monomers called nucleotides that consist of a Pentose sugar. Nitrogen-containing base. Phosphate. nucleotide

Nitrogen Bases The nitrogen bases in DNA and RNA are Pyrimidines C, T, and U Purines A and G.

Pentose Sugars The pentose (five-carbon) sugar In RNA is ribose. In DNA is deoxyribose with no O atom on carbon 2’. Has carbon atoms numbered with primes to distinguish them from the atoms in nitrogen bases.

HO A nucleoside Has a nitrogen base linked by a glycosidic bond to C1’ of a sugar (ribose or deoxyribose). Is named by changing the the nitrogen base ending to -osine for purines and -idine for pyrimidines. Nucleosides

A nucleotide Is a nucleoside that forms a phosphate ester with the C5’ –OH group of a sugar (ribose or deoxyribose). Nucleotides Is named using the name of the nucleoside followed by 5’-monophosphate

Nucleosides and Nucleotides with Purines

Nucleosides and Nucleotides with Pyrimidines

Primary Structure of Nucleic Acids

Structure of RNA The primary structure of RNA Is a single strand of nucleotides. Consists of the bases A, C, G, and U linked by 3’-5’ ester bonds between ribose and phosphate.

Structure of DNA In the primary structure of DNA, A, C, G, and T are linked by 3’-5’ ester bonds between deoxyribose and phosphate.

Data of Erwin Chargaff Chargaff’s Rules: %A = %T; %G = %C

X–Ray Diffraction Pattern of DNA Helical Cross

DNA Secondary Structure Double Helix

DNA Replication Watson-Crick Idea “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.” Watson, J.D and F.H.C. Crick Nature 171, (1953)

DNA Replication

Transcription: DNA to RNA

Transcription of mRNA

tRNA Structure

(Inducer) Induction of genes normally repressed

Negative Regulation (bound repressor + corepressor inhibits transcription) Repression of genes normally expressed corepressor

Posttranscriptional Processing of mRNA

Genetic Code

Protein Synthesis Amino Acid Activation Energize the amino acid. Costs equivalent to 2 ATP. Transfer energized amino acid to its specific tRNA.

Protein Synthesis Translation

Protein Synthesis: Role of Polysomes

Antibiotics: Inhibitors of Protein Synthesis Streptomycin: inhibits initiation and causes misreading of the genetic code Tetracyclines: inhibit binding of aa-tRNA Chloramphenicol: inhibits peptide bond formation Erthromycin: inhibits translocation

Mutations

Recombinant DNA

Polymerase Chain Reaction (PCR) heat to separate the two strands add primers, cool to 55 o C use DNA polymerase, to extend chains 5’ 3’ 5’ First Cycle Second Cycle heat to separate the two strands Third Cycle heat to separate the two strands add primers, cool to 55 o C add primers, cool to 55 o C use DNA polymerase, to extend chains use DNA polymerase, to extend chains

DNA Fingerprinting

Retrovirus Action

AIDS Virus and Treatment AZT (3’-azido-3’deoxythymidine) (nucleoside analog reverse transcriptase inhibitor) Examples of protease inhibitors: saquinavir, indinavir, ritonavir Examples of non-nucleoside reverse transcriptase inhibitors: etravirine, efavirenz, nevirapine