Objectives:
Compare and contrast:
Transcription and DNA replication
DNA and RNA
DNA polymerase and RNA polymerase
Transcription: Details of process including start and stop sites, components, and application
Coupling of transcription and translation
Difference between prokaryotic and eukaryotic RNA: including methods of RNA processing and coupling of transcription and translation
Translation: 4 components, details of process, and inhibitors of translation, and application
• Fig. 7-1: Flow of genetic information
• transcription - DNA ( RNA
• translation - RNA ( protein
I. How transcription differs from DNA replication: 1. Uses RNA polymerase 2. RNA strands do not remain hydrogen bonded to the DNA template after being transcribed 3. Only one strand of the DNA molecule is transcribed for a specific gene 4. RNAs are only copied from regions of the DNA that contain genes
DNA polymerase vs. RNA polymerase
|DNA POLYMERASE |RNA POLYMERASE |
|DNA replication |Transcription |
|Catalyzes linking of deoxyribonucleotides |Catalyzes linking of ribonucleotides |
|Needs RNA primers to start DNA synthesis (needs 3’-OH end) |Does not need primer to start RNA synthesis |
|Has proof-reading capabilities (1 error in 107) |Does not have proof-reading capabilities (1 in 104) |
Two types of Nucleic acids: DNA and RNA
|DNA |RNA |
|Deoxyribonucleotides (G, A. T, C) |Ribonucleotides (G, A, U, C) |
|Sugar = deoxyribose |Sugar = ribose |
|Thymine pairs with adenine |Uracil pairs with adenine |
|Double-stranded helix |Single-stranded |
|Cannot fold into various structures |Can fold into 3-D structures |
|Functions solely as information storage |Convey information; structural and catalytic functions | Transcription – synthesis of a mRNA from DNA
• 3 kinds of RNA: a. mRNA – directs the incorporation of amino acids into proteins; carries coded information for making proteins from DNA to the ribosomes b. tRNA – bring amino acids to the ribosomes where they are incorporated into proteins c. rRNA - forms the integral parts of ribosomes
II. The process of transcription: a. mRNA is synthesized using specific genes of the DNA as template b. RNA polymerase and a supply of RNA nucleotides are required
How does RNA polymerase know where to start transcription? Prokaryotes: 1. Transcription begins at the promoter at the 3’-OH end of a gene • Promoter consists of a -35 and -10 sequences • Sigma (σ) factor - A subunit of bacterial RNA polymerase responsible for recognizing the promoter sequence 2. DNA double helix unwinds at start of gene. a. Only one strand serves as template for RNA synthesis for a given gene because synthesis can only occur in 5’( 3’ 3. RNA polymerase adds ribonucleotides into the new chain using
