Life 201, Exam 1 Study Guide
Life 201, Exam 1 Study Guide Life 201
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This 35 page Study Guide was uploaded by Natalya Bracewell on Wednesday February 10, 2016. The Study Guide belongs to Life 201 at Colorado State University taught by Eric Ross in Winter 2016. Since its upload, it has received 66 views. For similar materials see Introductory Genetics in Biology at Colorado State University.
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Date Created: 02/10/16
LIFE 201, EXAM 1 Review/StudyGuide Derived fromStudyGuides provided by Eric Ross LECTURE 1 KeyConcepts andTerms CentralDogma Mendel • Usedpea plantsto provethe model of3:1 inheritance • Peasare ideal because they arediploid,manysinglegene traits, onetrait per organism,andtrue breeding • Discovered3 postulates 1) Unit factors come in pairs (alleles) 2) Random segregation during gamete formation 3) Traits are dominant or recessive Exception: height(and some others)arepolygenic—determined bymore thanone gene • Twolaws: 1. LAWOFSEGREGATION: During gamete formation, the 2 alleles of a gene separate and 1 is passed onto offspring 2. LAWOF INDEPENDENTASSORTMENT:Segregations of allelic pairs is independent Exception: haploid,tetraploid,anyorganism thatisNOTdiploid, theselaws don’t apply unitlawsassumediploid organisms and thatalleles aren’tclose together,thentheyarelinked andmoveas a Terms • Heredity: transmission of genetic info to • Allele: one of several forms of a gene offspring • Homozygote: diploid cell having two identical • Catalyst: a substance that accelerates a alleles of a given gene chemical reaction • Heterozygote: diploid cell having two different • Transcription: the copying of DNA to RNA alleles of a given gene • Translation: the generation of protein using • Unit factor of inheritance: the physical genetic RNA as a template material that is passed on to offspring • Replication: the copying of DNA •genes/chromosomes are unit factors for humans • Phenotype: observable characteristics that • Dominant: the member of a pair of alleles result from a combo of alleles that is phenotypically expressed when an organism is heterozygotic • Genotype: the combo of alleles present in an • Recessive: the member of a pair of alleles organism that is NOT phenotypically expressed when an organism is heterozygotic LECTURE 2 KeyConcepts Functions DNA RNA • Needs to: • mRNA is made anddegraded at a 1) Replicatefaithfully,fewmistakes rapid rate 2) Be stable(roughlysameinfoat the endoflife) • Decoding (ribosomes) 3) Storeinfo(genetic textbook) • Enzymatic activities! 4) Express info(encodeRNA to make proteins) • Many others…. 5) Change(variabilityby mutation) Capacity tochange between generations Experiments • 1927 –GRIFFITH: Bacteria can be transformed •Inserted 2 different strainsintomice:1 lethal,1 norm •Mixture ofnormstrain& lethalstrain= sickness •Changewasa result ofthe transferofgeneticmaterial • 1944 –AVERY: DNA is the transforming agent •MixedRNAor proteinwiththe R strain(non-lethal),nothinghappened •MixedDNA withthe R strain,it became a lethalstrain • 1952 – HERSHEY/CHASE: confirmed DNA to be genetic material •Isotopes:same #ofproteins& electrons, different # ofneutrons; different masses,same chemicalproperties •Isotopeswere used to label DNA andproteins,showedDNAwasinjected, not proteins StructuralFeatures DNA RNA • Double-helix •Single stranded • centralaxisotidechainscoiledarounda •Can from interesting, complex structures • 3.4Å between bases •Nucleotides have anOH group • Nucleotides haveanH • Basesare onthe inside,H-bonds •Morereactive,importantfor • A=T G=C enzymatic processes& instability • Sugar-phosphatebackbone •HasU notT •Differentchemicalproperties,Thymine • because goingoppositedirections onicate hasamethyl group strans) Contributions to DNAStructure • Rosiland Franklin • UsedX-raydiffraction,sawthe cross pattern,indicatingahelix • Knewsomethingimportantwasrepeated every 3.4Å because there were dark bands • 1953 –Watson &Crick published DNA model • Watson,Crick,Wilkins& Franklinallcontributed,WatsonandCrick just finallyput it all together • 1962 – Nobel Prize forChemistry • 8years afterthe paper,wasawardedtoWilkins,Crick,andWatson • Franklinhaddied, possiblyofradiationcausingovariancancer LECTURE 2 KeyConcepts NucleicAcid Hybridization • DNA absorbsUV light • Max at 260 nm • Interaction between ring system of DNA andUV light • Used to quantitate DNA • Hyperchromic effect: single strandabsorbs more light than double strand DNA DNAMelting • Temperature increases, separating DNA strands • Melting temp is 50% melted ( ½ are on, ½ are off) • Increase in absorbance as DNA is heated up • Melting temperature is dependent on: • Length • A=T,GΞC •GΞCconcentration ismore important because there ismore hydrogen bonds to melt NucleicAcidAnnealing • DNA melting is reversible • Slowly cool to anneal • Less errors, willhitthe optimum temperature to “lookin”correct structure • Quickcoolingwillcreateinstability • Hybridization: annealing ofANY two complimentary nucleic acid strands • Imperfect matches: depends on temperature or solution conditions CotCurves • Genomic DNA is fragmented, denatured, and re-annealed • See how quickly they come back together • More complex genomes re-anneal slower • Higher eukaryotes are bimodal (has a curve with two parts) •Genomes haverepeated sequences •1 curve: repetitive, 2 curve: singlecopy • 300,000DNA transposonsin human genome •Has alot ofbuddies, quicker to just findone • 45% of DNA genome are “junk” DNA FISH • Fluorescently labeled DNA inserted • Can label specific spots on the chromosome • DNA probes specific to a region of a chromosome • Need to know what you’re looking for • Microarray: monitor many genes at once, look at the entire genome andsee what’s different about it • Spectral karyotyping: FISH with different color fluorescent probes for each chromosome • Canspot translocation GelElectrophoresis • Migration under an electric field • DNA is negatively charged so it moves towards the positive charge • How far it migrates is based on size, shape, andcharge • Smallermoves farther, curved migrates slower VisualizingDNA onGels • Ethidium bromide • Morecommon • Inserted between DNAbases • Fluoresces • Goodfor onepair • Radioactively label • 32P atthe ends or inthe backbone(phosphate) Blotting • Pick out single band from a smear • Run gel & then find specific band of interest • Use paper towels to pull up the liquid • Now it’s usually done with a fluorescent probe, used to be radioactive •Burningpigincident….nomore radioactive • Different forms: •Southern:DNAprobe to detect DNA •Northern:DNAprobe to detect RNA •Western: antibodies todetect protein LECTURE 4-6 KeyConcepts MAINIDEA •Examinetheprocess of replication–how it occurs and whyit occurs thatway!!! Meselson&Stahl • Researched how genetic material is passed on (DNA) • Different theories: 1. Conservative 2. Semi-conservative 3. Dispersive • Used equilibrium sedimentation to prove semi-conservative was correct • N14andN15medium DNARepair 1. Watson-Crick base pairing • Reads 5’ 3’ 2. Exonuclease • Reads 3’ 5’ 3. Strand directed mismatch repair • Sees mismatchandfixes it • Recognizeswhichis thecorrect/originalstrandbecausethe new strandisnot methylated ReplicationChallenges • Fidelity (accuracy) •Problem: tautomers—H-bonddifferently andleadto mistakes •Solution:polymerasewillbackup andfix theproblem so itcanmove forward • Needsa properlypositionsOH groupto move on • 3’ 5’ exonuclease activity • Dealing with 2Strands •DNAjust copiesasit goes,the twostrands are anti-parallelbut polymerasecanONLYgo 5’ 3’ •Semi continuousreplication,forkis movingto the rightbut the other strandhasto go backwardonthelaggingstrandandreplicateinlittlepieces, OkazakiFragments •Problem: DNApolymeraseneeds aprimer •Solution:DNAprimase,anRNApolymerasethat doesn’t require aprimer • Makes a lotof mistakes,but better than losingwhole chunk of DNA • Removes and replaces RNA primer, still a break in the backbone that is sealed by ligase • Unwinding the DNA • DNAHelicaseunwindsthe DNA • UsesATP to openDNA • Problem: DNAleft openwillcreate secondarystructures, causehairpins • Solution:DNAiskept openby singlestrandbindingproteins • Not bonded superstrong,just enough to old itopen • Processivity (not falling off) • Problem: DNApolymerasecan’taffordtofalloffwhilesynthesizing • Solution:slidingclamp,likea seat belt to keep it on • Tangling • Problem: DNAis twistedarounditselfmanytimes andasit opens,tensionis created • Solution:DNATopoisomerases • Topo I:Clips one strand • Topo II:clipsboth strands, keepsends in closeproximity,doesn’t let the ends go DNASYNTHESIS • Helicase unwinds the DNA • DNA Primase anneals to both strands • 1 DNA Polymerase chugs away,building new DNA • 2 DNA Polymerase removes RNA primers • Ligase seals the nicks in the backbone ReplicationDifferences Prokaryotic Eukaryotic • 1 origin of replication • Multipleoriginsofreplication • LinearDNA • Circular DNA • About 100 nt/second • About 1000 nt/second • Occurs when there’s enough • Occurs intheSPhaseat different checkpoints nutrients • Replicationis initiatedinthe nucleus • Replication is initiated in the • Reinitiationis preventedby the original backbone DNAbeingmethylated • Telomeres andtelomerase areonly found ineukaryotes LECTURE 7 KeyConcepts DNADamage • Depurination: removal ofA/G • Deamination: removal of amino group, causes aC U transition • Pyrimidine dimers:UV light issues, occurs between neighboring pyrimidines (C orU) • Double-stranded breaks: DNA breaks in the sugar phosphate backbone DNARepair • Double stranded results in redundancy, basically two templates so one can serve as a back up • Most changes result in unatural bases, easy to recognize an issue • Strand directed mismatch repair • Excision repair LECTURE 8 KeyConcepts Recombination • Non-homologous end joining: chew back rough ends, ligase just seals the break • Quick,but DNAloss • Mostused because DNAlossis ofteninsignificantbecause onlyabout 2% ofDNAcodes for proteins • Homologous recombination: use homologous chromosome in one strand to fix the break in the broken one, flawless repair • Noloss,but canonlybe used intheSandG2 phases LECTURE 9 KeyConcepts Recombination • Site-specific • Reversible • Mechanism:breakage andinsertionat specificsites • Homologousat thesite ofinsertion • Example:bacteriophage BarbaraMcClintock •Discovered transposition, or “jumping genes”
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