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This 25 page Study Guide was uploaded by Noelle Murillo on Tuesday March 1, 2016. The Study Guide belongs to BIOL 190 at Towson University taught by Stella Evans in Fall 2015. Since its upload, it has received 53 views. For similar materials see Intro to Biology Health Profession in Biology at Towson University.
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Date Created: 03/01/16
Exam 1 BIOL 190 Watson & Crick’s DNA Structure Franklin’s x-ray of Chargaff’s amt. of Watson and Crick’s DNA nucleotide in DNA Summation • DNA is 2 strands • A amt. = T amt. w/ = distance • Shape and • G amt. = C. amt structure of apart DNA through • Nucleotide bases base pair rules point inwards 4 Diff DNA Features Nucleotides Purines Pyrimidines • Double helix – 2 polynucleotide strands Adenine, guanine Thymine, cytosine • 4 nucleotides – adenine, thymine, guanine, cytosine • Base pairs: A=T and G=C • Hydrogen bonded – A=T (2 bonds) < G=C (3 bonds) • Nucleotide structure – th • Phosphate and sugar bonded w/ 5 carbon Nucleotide • All DNA nucleotides have same phosphate and sugar Monomer of nucleic acid • Differ in nitrogenous base Phosphate 5 carbon Nitrogenous group sugar base (-) charged; “acAka deoxyribose A, T, G, C Complimentary Base Pairing • How cells make 2 identical copies of strands during cell division through transmission (think DNA replication b/c strands separate and partially recreate) • Side-side combo of nitrogenous bases that form rungs on double helix ea. w/ varied sequences (ea. gene has own order of nucleotide sequence) • DNA: adenine=thymine and guanine=cytosine Hershey & Chase’s Experiment • Question: How does T2 virus reprogram itself to make new phages? Protein or DNA? EXPERIMENT Protein DNA Mixed radioactively labeled phages w/ T2 (used phage type + sulfur phag+ phosphorus phage b/c already existing component) Blender to separate phages outside of bacteria from its cells and content Centrifuge (E. coli at bottom section) to form pellRadioactivity at topRadioactivity at bottom show radioactivity placement section section and injected to E.coli • Conclusion: DNA produces new phages DNA Replication: S1: Parent Strands Separate • Semiconservative model – 1 parent strand/molecule and 1 daughter strand/molecule attach by base pairs • 2 strand of parental DNA separate • DNA helicase – unwinds DNA strands • Origin of replication/bubble – short stretches of parent DNA w/ nucleotide sequence where protein attached is separated – occurs in various areas • Daughter molecule elongates self to speed up process DNA Replication: S2: Parent & Daughter Strands CBP • 2 daughter DNA molecules’ nucleotides line up w/ parents strands’ in accordance to base pairs while elongating • DNA sugar-phosphate backbone run in opp. direction – w/ ea. strand having 3 and 5 end • DNA primase – begins replication by preparing area for DNA polymerase (having something to hold onto) • DNA polymerase add nucleotides to 3 end b/c DNA strand growth 5→3 (start where left off) • Lagging strand creates Okazaki fragments and linked together by DNA ligase to create single DNA strand • Enzymes link nucleotides = 2 new DNA strands DNA Replication Enzymes • DNA primase – begins replication by preparing area for DNA polymerase (have something to hold onto) • DNA polymerase – assembles and links DNA nucleotides to growing daughter strand using parent strand as template, and proofread own work b/c 1 nucleotide error for every several billion nucleotides • DNA helicase – unwinds the DNA • DNA ligase – glues Okazaki fragments together to form single DNA strand DNA Replication at Both Directions • Each DNA sugar-phosphate backbones in opposition to each other = opposite 5→3 ends • Recall 5 carbon sugar and its prime carbons – whichever closest to end determine number of end • Faster process Nucleic Acids DNA vs. RNA DNA RNA • Double stranded • Single stranded • No CBP to other RNA strand, • Sugar – deoxyribose instead, paired w/ DNA strand • Nitrogenous bases – A, T, G, C • Sugar – ribose • Base pairs – A=T and G=C • Nitrogenous bases – A, U, G, C • Base pairs between RNA and DNA – A=U and G=C • RNA-RNA not paired b/c RNA single stranded Transcription: DNA → RNA • Transcription – transfer of genetic info from DNA to RNA occurring at nucleus • INITIATION • 2 DNA strands separate at promotor – specific binding site for RNA polymerase and determines which DNA strand used as template b/c diff sequence for diff strand = diff protein • RNA polymerase covers DNA and begins synthesis (link nucleotides) T ranscription • ELONGATION • RNA nucleotides form base pairing H-bonds w/ DNA strand through RNA polymerase • RNA strand grows longer by it “peeling” away from DNA template = 2 DNA strands reunite (unwinds then rewinds) together after RNA polymerase moves • TERMINATION • RNA polymerase reaches terminator – sequence of bases in DNA template that signals end of gene • RNA polymerase detaches from DNA strand, RNA molecule, and gene RNA Molecule After T ranscription • RNA molecule undergoes process that creates mRNA – type of RNA that encodes genetic info from DNA and conveys it to ribosomes, where info translated to amino acid sequence • Ends added to protect mRNA from attacking enzymes and help ribosomal bind • G-cap and Poly-A Tail • RNA splicing – cut introns (noncoding) and splice exons (coding/expressible region = mutation visible) together • New mRNA strand enters cytoplasm through nuclear pores Codons from mRNA for Amino Acids • mRNA contain codons – 3 nucleotide sequence in mRNA that specifies particular amino acid • 20 amino acids • 64 codons including STOP codons • 61 codons that code for amino acids • AUG – start codon • encode 1 amino acid)cid has multi encoders) not ambiguous (1 codon only Different RNA’s from T ranslation • Transfer RNA (tRNA) – converts RNA/mRNA/codon to language of amino acid proteins – “molecular interpreter” • Nucleotides → amino acid function • Why tRNA? Cell produces proteins in cytoplasm from food/chemicals • Protein’s amino acid CANNOT recognize mRNA’s codons • Then what? tRNA molecules must match amino acids to appropriate codons to form polypeptide • How? tRNA has anticodons - specific sequence of 3 nucleotides complimentary to mRNA’s codons Different RNA’s for Translation • Ribosomal RNA (rRNA) – w/ protein, makes up ribosomes in form of 2 subunits • Ribosomes in translation • Has 1 binding site for mRNA and 2 binding sites (A site and P site) for tRNA • Subunits hold tRNA and mRNA molecules close together T ranslation: RNA→Protein • INITIATION 1 • mRNA binds to small ribosomal subunit • tRNA binds to start codon w/ its anticodon and carries Met • INITIATION 2 • Large ribosomal subunit binds to smaller subunit = ribosome becomes functional • Initiator tRNA fits into 1 of 2 sites – A site of the ribosome T ranslation: RNA→Protein • ELONGATION: amino acids added 1-1 to previous amino acid • Codon Recognition • Initial tRNA anticodon w/ amino acid pairs w/ mRNA’s codon at A site • Polypeptide Bond Formation • Initial tRNA moves to P site for incoming tRNA to be move to A site •amino acid of tRNA in A sitelypeptide) detaches from initial tRNA and attaches to the • Ribosome catalyzes formation of polypeptide bond T ranslation: RNA→Protein • ELONGATION • Translocation • Initial tRNA leaves ribosome • Ribosome moves tRNA from A site to P site w/ its growing polypeptide • tRNA and mRNA move as unit = codon and anticodon remain H-bonded • Next mRNA codon brought to A site for new tRNA • Cycle repeats until STOP codon reached Mutations • Any change in the nucleotide sequence of DNA • Nucleotide change = codon change = amino acid sequence change • w/in genes – have 2 categories • Substitution – change 1 amino acid Mutations w/in Genes • Insertion/Deletion – change 1 = change ALL Nucleotide Nucleotide Substitution Insertion/Deletion Replace nucleotide and its base pairct nucleotide = alter partner w/ other nucleotireading frame (codon group) Mutations • More of nucleotide substitution Nucleotide SubstReplace nucleotide and its base pair partner w/ other nucleotide pair Silent Missense Nonsense Mutation Mutation Mutation amino acid = unchanged seqamino acid = altered sequenpolypeptide and improper functionlete effect effect Mutagenesis • Production/cause of mutation • Errors in DNA replication or recombination • Mutagens – physical (high energy radiation) or chemical (similar to DNA bases but cause incorrect paring) agents Gene Regulation • The turning on/off of genes in response to environmental changes • Operon – cluster of genes w/ related functions and control sequence that control transcription; unit of gene regulation in prokaryotes • Components: • Regulatory gene – codes for repressor and controls transcription of other gene/gene group • Promotor – site where RNA polymerase attaches and starts transcription • Operator – (not) allows promotors action “switch” • Repressor – protein that bind to operator and physically block attachment of RNA polymerase and promotor (OFF – blocking ON – not blocking) • Enzymes – start metabolizing substance Gene Regulation • Lac Operon • Lactose present – operon ON • Lactose absent – operon OFF • Trp Operon • Trp present – operon OFF • Trp absent – operon ON (make own) Gene Expression: X Chromosome Inactivation • Barr body – female’s inactive X chr in each somatic cell • Inactivate X chr = inactivate ALL descendants chr b/c epigenetic inheritance • Epigenetic inheritance – inheritance of traits transmitted not involving nucleotide sequence • Active X chr will activate randomly w/in descendants
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