MIC 205 1st Edition Lecture 14 Outline of Last LectureI. DNA ReplicationII. DNA TranscriptionIII. Translation of mRNAOutline of Current Lecture IV. Wrap up Microbial Geneticsa. Translation cont.V. Control Genetic ProcessCurrent Lecture Translation:- tRNAo acceptor stem = portion of tRNA that is linked to amino acido anticodon = nucleotide triplet complementary to the mRNA codon for a given tRNA’s amino acid Each tRNA carries a specific amino acid and recognizes an mRNA codon specifically for that amino acido Bacterial ribosomes are 70s Ribosomes Different (smaller) than eukaryotic ribosomes that are 80s RibosomesTranslation Step #1 - Initiation:o Ribosomal subunits assemble on mRNA transcript and recruit an initiator tRNA molecule Translation Step #2- Elongation:o Ribosome recruits an amino acid bound tRNA according to sequence of mRNA template (growing polypeptide—connected by peptide bonds)Translation Step #3- Termination: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.o Stop codon and special release factors sever the polypeptide from the last tRNA***In bacterial cells replication, transcription and translation they all occur in the cytoplasmLecture task:o 1) This molecule is an output of replication and an input of transcription: DNAo 2) This organism maintains its genome in a single circular chromosome: BacteriaControl of Genetic Process**Regulation of Gene Expression**o Cells need to keep track of genetic info and utilize it carefully ¾ of all genes are expressed ALL THE TIME (housekeeping genes) Other genes are regulated so only transcribed and translated when the cell needs them Allows energy conservation (they are turned off till needed) Cytoplasm isn’t crowded with unused enzymeso Cells stop making a protein by shutting down transcription If necessary they halt all translation directlyProkaryotic Operonso Cluster of genes with regulatory unitso Promotor, Operator, Structural genes Structural genes: code for functional proteinso Inducible- normally off and kick it then it turns on EX) lactose (lac) operon o Repressible- normally on and kick it then turns off EX) tryptophan (trp) operonMutation of Genes- Change in nucleotide base sequence of an organism’s genome- Most changes just delete parts of the sequenceo 2 main types1. Point Mutations- (most common) - Affect only one or a few base pairs at a time2. Frameshift Mutations- Nucleotide triplets after the mutation displaced so the reading of thecodons is altered (insertion or deletion of nucleotide)- Radiationo Non ionizing (low energy induce thymine dimers)o Ionizing (high energy induces breaks in chromosomes)DNA Repair Mechanisms:- Excision repair- removing damaged DNA and replacing it with new strandDNA Recombination and Transfer- Genetic recombination = Exchange/rearrange DNA segments- Recombinants = cells with DNA molecules with new nucleotide sequences- Vertical gene transfer = pass generationally down to descendants- Horizontal gene transfer = donor contributes only part of genome to recipiento Three types (microorganisms can perform)1. Transformation- Griffith’s experience on mice with pneumonia o Transforming agent is DNA Cells that take up DNA = competent cells Competency results from alterations in cell wall that allow DNA to enter cell- Can acquire new characteristics2. Transfuction3.
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