BIOL 1107 1nd Edition Lecture 13 Outline of Last Lecture I Genotype and Phenotype a Dominance b Alleles II Codons III Mutations a Point mutation Missense Silent mutation b Chromosome level mutation Outline of Current Lecture I Primary Transcription II Initiation a Prokaryotes b Eukaryotes III Splicing IV tRNA Current Lecture I Primary Transcription RNA is used as a template strand for DNA RNA has uracil U while DNA has thymine T however it s okay because U behaves chemically the same as T The new RNA template s called the primary transcript result of copying DNA with RNA polymerase the primary transcript in a prokaryote is mRNA o Primary transcript in eukaryotes is not an mRNA until primary transcript is processed through RNA processing Bacteria only has one type of polymerase while eukaryotes have three types of RNA polymerase II Initiation initiation is the first phase of transcription a Prokaryotes Sigma a protein subunit must first bond to the polymerase to initiate transcription sigma acts as a regulatory factor guiding RNA polymerase to specific promoter sequences on the DNA template strand 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 Sequences of the gene are upstream in the opposite direction of RNA polymerase movement during transcription acting as their own regulatory elements Operon cluster of functional genes that are upstream Regulators are promoters highly conserved across species and organisms RNA polymerase does not physically come in contact with DNA There are different sigma s for different proteins The cell controls transcription by not allowing certain sigma proteins to bind to promoter o As soon as they do bind it s over it goes onto promote transcription End of initiation is seen by a loop in the strand no longer allowing the polymerase to move down the strand b Eukaryotes A group of proteins called basal transcription factors bind to DNA promoter thus initiating transcription End of initiation is seen by a three signal sequence III Splicing The transcription of eukaryotic genes by RNA polymerase generates a primary RNA transcript that contains exons and introns introns are removed by splicing RNA processes go into strand and cut out regions in the gene that are not necessary for the production of a particular protein exons are left behind then the exons are reunited when done it goes from primary transcript to mRNA Can build different proteins by the same gene through splicing by introducing introns and exons into the gene The deleted protein is taken and a 5 cap is added to one end and a Poly A tail is added to the other side A small ribosomal subunit smRNA recognizes the 5 cap 5 cap serve as a recognition signal for the translation machinery The Poly A tail extends the life of an mRNA by protecting it from degradation IV tRNA o ATP is required to attach tRNA to an amino acid o Enzymes called aminoacyl tRNA synthstases charge the tRNA by catalyzing the addition of amino acids to tRNA s for each of the 20 amino acids there is a different aminoacyl tRNA synthetase and one of more tRNAs The tRNA covalently linked to its corresponding amino acid is called an aminoacyl tRNA Ribosome is a complex that is not incased in a membrane When this process is done most ribosomes are dissembled
View Full Document
Unlocking...