DNA Replication Transcription and Translation Every great advance

DNA Replication, Transcription and Translation

“Every great advance in science has issued from a new audacity of the imagination” - John Dewey

Eucaryotic DNA and RNA 3 -5% of genomic DNA is coding or informational Only a portion of DNA is transcribed into RNA makes up about 1/2 of the nucleic acid/cell r. RNA is the most abundant ≈ 90% With protein it assembles into ribosomes, site of translation m. RNA is about 2 -3% of the RNA Has poly A attached at the 3’ end Has a 5’ methyl cap May require processing and splicing t. RNA carries amino acids to ribosomes

DNA replication Four nucleotide bases Nucleotide triphosphates Phosphodiester bonds 5’ to 3’ DNA structure Hydrogen bonds, complementary base pairing A pairs with T G pairs with C Double stranded structure

DNA Four nucleotide bases

Nucleotide

DNA Replication

Nucleotide Polymerization Template Primer DNA polymerase 5’ to 3’ polymerization

Leading & Lagging Strand Replication Leading Strand • Continuous replication Lagging Strand • Discontinuous replication Okazaki fragments RNA primers

Procaryotic Replication RNA primers Dimer of Polymerase III polymerizes DNA polymerase I repairs Okazaki fragments Primosome • DNA helicase • DNA primase SSB proteins

Eucaryotic DNA Replication Dimer of DNA polymerase d polymerizes Primosome • DNA polymerase a/primase • Helicase RNA primers SSB proteins

Bidirectional Replication Polymerase III dimer Continuous replication Discontinuous replication

Telomere Replication

3 D Packing of Human DNA

Central Dogma---DNA RNA Protein

Transcription

RNAs r. RNA-class I gene in eucaryotes m. RNA-class II genes in eucaryotes t. RNAs-class III genes in eucaryotes Other RNAs • sno. RNAs • cytoplasmic stable RNAs

Basic Transcription Initiation Elongation Termination

Procaryotic Transcription A single RNA polymerase • Sigma factors give specificity Sensitive to Riframpicin antibiotic Coupling of transcription & translation Polycistronic m. RNAs No introns Pribnow box involved in initiation

Eucaryotic Transcription Three RNA polymerases • RNA pol I-r. RNA • RNA pol II-m. RNA • RNA pol III-t. RNA Pol II & III sensitive to mushroom toxin a-amanitin Transcription & Translation separated • Spacial • Temporal Exons & Introns TATAA box involved in initiation

Life Cycle of an m. RNA Transcription Modification • Methylation • Poly A addition Processing Export Translation Turnover

RNA Splicing sn. RNPs 5’, 3’splice sites Branchpoint Spliceosome Transesterification #1 Transesterification #2 Lariat formation Spliced exons Turnover

RNA Splicing Dynamics