ZOL 341 Lecture 6 Outline of Last Lecture I Replication II RNA III Process of bacterial transcription IV Transcription termination Outline of Current Lecture II Transcription factors III Sequences IV Post transcriptional processing V Ribosomes Current Lecture transcription factors TFs RNA polymerase II recognizes and binds to promoter sequences with aid of TF proteins example TATA box sequences enhancer increase the level of transcription of specific genes bind proteins that interact with the proteins bound to promoters may be variable distances from the genes they affect upstream or downstream silencer DNA elements that act at a distance to repress transcription bind repressor proteins that induce bends in DNA may be variable distances from the genes they affect upstream or downstream post transcriptional processing of RNA molecules turns premRNA to mature mRNA 1 5 capping after the first 20 30 nucleotides of mRNA have been synthesized a 7methylguanosine is added to the 5 end of the pre mRNA These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute protects mRNA from rapid degradation facilitates transport of mRNA out of the nucleus facilitates subsequent intron splicing enhances translation efficiency by orienting the ribosome on the mRNA 2 3 adenylation enzyme action removes a section of the 3 end and replaces it with a string of adenines facilitates transport of mature mRNA across the nuclear membrane to the cytoplasm protects the mRNA from degradation enhances translation by enabling the ribosomal recognition of mRNA 3 Intron splicing introns are removed from the pre mRNA by an snRNA protein complex called the spliceosome the 5 splice site is cleaved first and a lariat intron structure is formed when the 5 intron end binds to the branch point adenine alternative intron splicing processing of identical trnascripts in different cells can lead to mature mRNAs with different combination of exons and thus different polypeptides increases the complexity of the proteome without increasing the number of genes all 3 processes are carried out simultaneously ribosomes machines that contain multiple rRNAs and proteins translate mRNA in the 5 3 direction bind mRNA and identify the start codon facilitate complementary base pairing of mRNA codons and the corresponding tRNA anticodons catalyze formation of peptide bonds between amino acids on the growing polypeptide chain composed of 2 subunits large and small ribosomal subunit
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