Exam 3 Study Guide
Exam 3 Study Guide BIOL 3301H
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This page Study Guide was uploaded by Kelli Restivo on Monday November 30, 2015. The Study Guide belongs to BIOL 3301H at University of Houston taught by Dr. Newman in Fall 2015. Since its upload, it has received 34 views. For similar materials see Honors Genetics in Biology at University of Houston.
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Date Created: 11/30/15
Honors Genetics Exam 3 Review Chapter 7 DNA Replication A B C IV VI A B Steps melt helix then base pair until a ddNTP is incorporated then stops Meselson and Sta h distinguished the mechanism of DNA replication 2 strands separate and EACH one acts as template for new strand each molecule contains one newone old strand Conservative the ENTIRE DNA molecules acts as a template one molecule is entirely conservedone synthesized Dispersive synthesized in short pieces alternating from one strand to another each STRAND of each molecule is a mixture of both new and old DNA Prokaryotes ONE origin of replication called AT rich Replication proceeds in BOTH directions around the circular chromosome Eukaryotes MULTIPLE origins of replication large protein complex containing enzymes for replication prevents supercoiling of DNA in front of helicase breaks hydrogen bondsunwinds DNA double helix prevent reannealing behind helicase 4 type of RNA polymerase that makes RNA primer 5 3 leading strand has ONE primer lagging strand has MANY 5 TWO of these for EACH replisome one for leading one for lagging 6 removes primer and replaces with DNA 7 joins Okasaki fragments together on lagging strand Telomeres ends of chromosomes has tandem repeat sequence Problem with lagging strand synthesis 3 overhang telomeres solve this problem adds additional nucleotides to 3 end because it has an RNA template that lengthens the DNA strand 1 Active in germline cellscancer cells NOT in normal somatic cells Polymerase Chain ReaLtion PCC in vitro method for replicating DNA Materials DNA dNTP primers and high temperature withstanding DNA polymerase Thermus aquaticus Steps denaturation of DNA annealing of primers to template and extension of primer sequence by DNA polymerase 1 Each cycle DOUBLES number of DNA molecules nger Sequencing dideoxy sequencing replication performed with nucleotides that DO NOT allow DNA chain to grow no 3 hydroxyl group to add new nucleotides 1 Bases of SEQUENCED strand can be read from bottom to top on a gel Chapter 8 Transcripti I II A B C III A B C D RNA ribonucleic acid contains uracilribose single stranded Transcription RNA synthesis uses instead of DNA polymerase Nontemplate strand coding strand basically identical to synthesized mRNA DNA sequencebinding site for RNA pol UPSTREAM of start site sigma subunit binds to RNA pol core enzyme either 35 or 10 TATAAT this is Where RNA p x polymerase binds 3 DNA unwinds near transcription start site 1 Steps promoter recognition initiation elongation termination 1 Initiationelongation holoenzyme starts at 1 then after 810 base pairs it dissociates from the core DNA unwinds AHEAD of RNA pol and reforms BEHIND it 2 Termination sequence is reached Eukaryotes transcription in NUCLEUSmodification occurs BEFORE export RNA pol II transcribes mRNA 2 other types of RNA pol I and III Promoter recognition 3 types of consensus sequences TATAAT CGCGCG CAAT Transcription factors DNA binding proteins in uence transcription 1 TFII interacts With RNA pol II binds to TATA box 2 General transcription factors bindrecruit RNA pol II 3 genespecific sequences Posttranscription modification With 5 cap 3 tail and intron splicing 1 guanine is added to 5 end then methyl group added to guanine protects mRNA from degradationhelp cellular transportorient ribosome 2 form polyA tail after a signal sequence AAUAAA signals the binding of cleavage factors removes intervening sequencesjoins EXONS done by splicesomes contain snRNPs can form MANY proteins from ONE gene 3 Chapter 9 Translation A B C D Proteins amino acids joined by peptide bonds covalent bonds between amine and carboxyl groups triplet nucleotides that code for amino acids Ribosomes bind mRNAstart codon read mRNA in 3 direction catalyze complementary base pairing codonanticodon and peptide bonds Sites A site P site E site Steps 1 Initiation involves start codon small subunit charged tRNA and large subunit joins after a few steps IN E COLI gt 6 nucleotides UPSTREAM from start codon Small subunit binds start codon Initiator tRNA Nformylmethionine binds in P site Large subunit joins IN EUKARYOTES Small subunit binds to initiation factors to make initiation complex gt Initiation complex binds to mRNAlooks for start codon which is in the Large subunit joins 2 Elongation involves A site next tRNA s enter P site hold tRNA with growing polypeptide and E site tRNA exit 3 Termination stop codon at A SITE no tRNA binds release factor polypeptide detaches D multiple ribosomes translating the SAME mRNA E refers to PROKARYOTES with multiple polypeptideproducing segments in their mRNA F Genetic code is but NOT ambiguous one amino acid can be encoded by MANY codons but each codon specifies ONE amino acid G ThirdBase Wobble exible base pairing at wobble position doesn t HAVE to be complementary base pairing at this position but must be purinepyrimidine AGGAGG Chapter 12 DNA Mutation I Mutation change in DNA sequence A Spontaneous natural B Induced interaction of DNA with physical chemical or biological agent 1 Chemical mutagens base replacement C single basea small few of bases change 1 D insertiondeletion base pairs addedremoved 1 Can change codons at single point or all codons downstream from it if it changes reading frame E one base pair replaced by another 1 Transition purine base replaced by another purine pyrimidine by pyrimidine Ex AG CDT 2 Transversion purine replaced by pyrimidine Ex ADT F different amino acid put in place of normal one 1 Conservative new amino acid is similar to intended amino acid 2 Nonconservative new amino acid is way different from normal 3 Nonsense codon mutates to stop codon no amino acid produced G mutations H mutations decreaseincrease AMOUNT of polypeptide produced does not affect sequence happens in NONCODING regions 1 Promoter mutations alter promoter consensus sequences TATADTACA 1 Chemical mutagens cause 1 2 Base replacement nucleotide analog causes mispairing Base alteration chemical modifies existing base J DNA Repair Systems 1 2 3 4 Proofreading DNA pol 3 5 exonuclease activity Mismatch repair fixes new DNA Homology dependent ALL of these use TEMPLATE to guide repair Nonhomologous end joining NHEJ When both strands damaged this method fixes it but it s still error prone Chapter 14 Gene Regulation in Prokarvotes I Transcriptional Regulation A Negative control involves REPRESSOR Which binds to OPERATOR transcription usually ON B Positive control involves ACTIVATOR protein that promotes transcription transcription usually OFF 11 Lac Operon set of genes that code for permeasebeta galactosidase breaks down lactoseglucose and galactose A collectively the PROMOTER OPERATOR and STRUCTURAL GENES B Jacob and Monod 1950 figured out lac operon mechanism 1 2 4 Lactose ABSENT repressor binds to operator NO transcription Lactose PRESENT repressor binds to allolactosecannot bind to operator transcription occurs Glucose ABSENT high levels of cAMP CAP binds cAMP and promoter transcription occurs Glucose PRESENT low levels of cAMPCAP does not bind not much transcription Transcription requires lactose present glucose absent C isolate mutants found constitutive continuously transcribing mutants 1 affect OPERATOR mutation in uences gene only on SAME chromosomes 2 mutation codes for proteins that in uence transcription in other chromosomes affect REPRESSOR III Tr Operon 5 structural genes for tryptophan synthesis transcription usually ON unless excess tryptophan A Negative regulationrepressible Chapter 15 Gene Regulation in Eukarvotes I Transcriptional regulation much more complexvaried A PROTEINS that bind consensus sequences 1 Activators bind to core promoterenhancer stimulate transcription 2 Repressors bind to silencers inhibit transcription B DNA SEQUENCES bind regulatory proteins 1 Farther from promoter better 2 In uence specific transcription C DNAprotein complex in eukaryotic chromosomes structure affects transcription need OPEN chromatin 1 positively charged proteins that DNA Winds around 2 Heterochromatin densely packedcondensed DNA 3 loosely packed more transcription 4 Chromatin structure can CHANGE Chromatin remodeling nucleosomes literally MOVEslide Chromatin modification histones chemically change by addingremoving functional groups to Nterminal tails D Alternative promoters used to make different premRNA iore promoter region immediately upstream of start site bound by
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