Bio 240 Chapter 14 Notes!
Bio 240 Chapter 14 Notes! Bio 240
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This 0 page Class Notes was uploaded by Izabella Nill Gomez on Thursday November 5, 2015. The Class Notes belongs to Bio 240 at University of Tennessee - Knoxville taught by Dr. Hughes in Summer 2015. Since its upload, it has received 15 views. For similar materials see General Genetics (Bio 240) in Biology at University of Tennessee - Knoxville.
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Date Created: 11/05/15
Biology 240 Chapter 14 Notes Translation biological polymerization of amino acids into polypeptide chains Occurs only in association with ribosomes which are the workbenches of this process tRNAs are a class of molecules that adapt to genetic information presented as codons and pairs with complementary anticodons to produce an amino acid chain during translation Ribosome consists of 2 subunits one large and one small Contain an array of ribosomal proteins When both associated become a monosome In prokaryotes ribosome is a 705 particles S for Svedberg coef cient and eukaryotic is 805 rRNA genes called rDNA part of moderately repetitive DNA category and present in clusters in many chromosome sites Each cluster consists of tandem repeats each unit separated by spacer DNA in humans near ends of chromosomes Cloverleaf model of tRNA has characteristic secondary structure based on base pairing Resembles cloverleaf Loops contain modi ed bases that do not generally pair anticodon loop 339 end of tRNA contains CpA adenosine residue 539pG contains guanine 339 end is the acceptor region where the amino acid is linked Before translation proceeds tRNA is charged by becoming chemically linked to its speci c amino acid under enzymes aminoacyl tRNA synthetases Amino acid reacted with ATP to create aminoacyladenylic acid Covalent linkage formed between 539phosphate group of ATP and carboxyl end of amino acid Occurs with synthetase enzyme forming complex that binds to speci c tRNA Amino acid transferred to 339 end where adenine residue located Charged tRNA then participates in protein synthesis Initiation factors bind to the small subunit and attract the mRNA molecule binding to a sit before the AUG start codon ShineDalgarno sequence In E coli Initiating Factor 1 blocks the A site of the small subunit of the ribosome from binding to the tRNA and IF 3 inhibits the small unit from associating with the large one Stabilized in P site the charged tRNA pairs with start to set the reading frame Upon release of IF 3 the complex forms and translation begins In elongation the second tRNA enters the ribosome A site to pair with a codon transported by one of the elongation factors The terminal amino acid in the P site forms a covalent bond with the amino acid of the A site to start a polypeptide chain elongation Uncharged tRNA moves to the E site where it is ejected and to be recharged by another speci c amino acid The process repeats until a stop codon is reached from mRNA and the polypeptide is formed Terminal codon signals action of GTPdependent release factor which stimulates hydrolysis of the polypeptide from the tRNA leading to release Then ribosome dissociates Polyribosomes occur with mRNA that has already passed through one ribosome and begins to associate with another occurs only in bacteria In eukaryotes translation occurs on larger ribosomes whose rRNA and protein are more complex Prokaryotic and eukaryotic RNA share core sequence but in eukaryotes lengthened by expansion sequences which add to functionality ln eukaryotes transcription and translation are separate cannot be coupled Transcription is in nucleus and translation is in cytoplasm 539 end of mRNA is capped with 7mg unlike prokaryotes must be processed before translation can occur Kozak sequence analogous to ShineDalgarno in prokaryotes as it is found upstream in eukaryotes Poly A tail on the 339 end of mature mRNA prevents degradation by nucleases Eukaryotic mRNA longer lived greater number of elongation factors used overall eukaryotes are more complex for translation Physician Garrod looked into research of alkaptonuria disruption in the metabolic pathway of of alkapton leads to darkening of cartilage and if not careful leads to arthritic condition Genetic in nature found mostly in consanguineous relationships Phenylketonuria PKU also metabolic disorder can result in mental retardation autosomal recessive Af icted individuals unable to convert phenylalanine into tyrosine Reaction catalyzed by enzyme phenylalanine hydroxylase inactive in affected individuals Accumulated phenyl Converts to acid badly absorbed affects brain levels of balance Beadle and Tatum provided rst convincing experiment con rming genes directly responsible for producing enzymes now known as one gene one polypeptide Worked with Neurospora and induced mutations to watch how they could grow on different mediums None of the mutants could grow on minimal medium because unable to synthesize certain proteins due to damaged genes Nearly all enzymes are proteins but not all proteins are enzymes BeadleTatum hypothesis modi ed to one gene one polypeptide hypothesis First proof came from studying sickle cell anemia Due to low oxygen tension that causes hemoglobin to become elongated Beet demonstrated the effect of dosage compensation in heterozygotes sicklecell trait Those not completely affected experience some symptoms but still had function of the hemoglobin due to availability of gene product Experimented with starch gel electrophoresis Fingerprinting technique allowed analysis of amino acid composition and digestion of protein into fragments Establishes that a single gene codes for a speci c polypeptide Order of nucleotides corresponds to the order of amino acids in a polypeptide collinearity Four levels of protein structure Primary structure speci ed by sequence of deoxyribonucleotides in DNA through an mRNA intermediate Helps determine speci c characteristics of higher orders of organization as a protein is formed Secondary structure regular or repeating con gurations in space assumed by amino acids lying close to one another in the polypeptide chain Ex alpha helix in DNA Proteins can have mixt of alpha and beta pleated sheet structures Tertiary structures three dimensional spatial conformation of the chain as whole Quaternary structure applies only to those that have more than one polypeptide chain Proteins in different roles Hemoglobin and myoglobin are involved in oxygen essential for cellular metabolism Collagen and keratin associated with skin connective tissue structural components Actin and myosin are contractile proteins involved in muscle tissue tubulin in function of microtubules during meiosis and spindle bers Transport proteins involved in movement of molecules along the cell membrane
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