BIOL 2051 Study Guide - Sigma Factor, Ribonucleotide, Ribosome
Document Summary
Transcription- making an rna copy of part of a dna strand. Dna- made of deoxyribonucleotides: double stranded, thymine, sugar-deoxyribose. Rna- made of ribonucleotides: single stranded, uracil, sugar-ribose. 3 main types of rna: messenger rna (mrna) Average 1000-1500 bases long: transfer rna (trna, ribosomal rna (rrna) transcribing dna into rna at that site, bacterial rna polymerase. 4 subunits: alpha (2 copies), beta, beta prime, sigma. Function is to help core enzyme locate promoter. Carries amino acids to the ribosome to build a protein during translation. Multiple sigma factors (over 100 known so far from numerous species) Housekeeping sigma factor used for most essential genes sigma^70: sigma^32. Active when cell is stressed by heat (heat-shock response) Transcription initiation: sigma factor binds core rna polymerase. Forms rna polymerase holoenzyme: rna polymerase binds promoter. 10 and 35 bases upstream of start site: polymerase unwinds dna at promoter. 1st ribonucleotide base pairs to dna at +1 position.