!PCB3063!Summer!2014!!!1!Chapter!1:!Introduction!to!Genetics!!Introduction!• December!1998:!deCODE!Genetics!was!granted!the!right!to!access!the!medical!records!of!270,000!Icelandic!residents!to!create!a!dat a base.!They!crossDreferenced!this!information!with!the!Health!Sector!Database!as!well!as!the!genealog ical!database!from!the!National!Archives.!Ended!in!2012.!• Other!largeDscale!databases!have!developed!in!Great!Britain,!Est onia ,!Latvia!and!the!Kingdom!of!Tonga.!• Used!to!analyze!human!genes!for!susceptibility!to!diseases.!• Iceland!was!selected!due!to!the!high!level!of!genetic!relatedness!within!its!population,!which!began!1000!years!ago!from!Scandinavian!and!Celtic!sources.!In!addition,!the!health!care!system!is!stateDsupported!which!allows!for!good!medical!records.!• Causes!debates!over!privacy,!consent!and!commercialization.!!1.1 Genetics!has!a!Rich!and!Interesting!History!Introduction!• Domestication!of!animals!and!cultivation!of!plants!lends!itself!to!the!recognition!of!traits!many!years!ago.!• On#the#Seed#by!Hippocrates!suggested!that!”humors”!in!the!male!parts!of!the!body!accounted!for!offspring’s!traits.!• Aristotle!proposed!that!the!male!semen!contained!“vital!heat”!which!produced!offspring!similar!to!the!parent.!!1600B1850:!The!Dawn!of!Modern!Biology!• 1600s:!William!Harvey!proposed!epigenesist!in!which!an!organism!follows!developmental!events!following!fertilization!of!an!egg.!• Contradicts!preformation:!the!fertilized!egg!contains!a!miniature!adult!called!a!homunculus.!• 1830:!Matthias!Schleiden!and!Theodor!Schwann!proposed!cell!theory:!organisms!are!composed!of!basic!units!called!cells!that!are!derived!from!similar!preexisting!structures.!• Spontaneous!generation:!creation!of!living!organisms!from!nonDliving!components;!disproved!by!Louis!Pasteur.!!Charles!Darwin!and!Evolution!• The#Origin#of#Species!published!in!1859!by!Darwin!describing!evolutionary!ideas.!• He!believed!existing!species!evolved!over!time!from!preexisting!ones.!• Natural!selection:!the!most!favorable!traits!will!be!carried!on;!explanation!for!mechanism!of!evolutionary!change;!based!on!the!observation!of!Alfred!Russel!Wallace!that!an!environment!has!more!organisms!than!it!can!support,!leading!to!competition;!individuals!that!can!adapt!and!posses!heritable!traits!survive.!• Darwin!lacked!genetic!knowledge!of!varia t ion!and!inheritance.!!!PCB3063!Summer!2014!!!2!• Gregor!Mendel!published!his!paper!on!the!inheritance!of!traits!using!pea!plants!in!1866.!Showed!how!traits!are!inherited.!His!research!was!not! w ell!known!until!1900s.!• Chromosomal!theory!of!inheritance:!closed!the!gap!in!Darwin’s!theory;!heredity!and!development!depend!on!genetic!information!in!genes,!contained!in!chromosomes!and!passed!on!through!gametes.!!1.2 Genetics!progressed!from!Mendel!to!DNA!in!less!than!a!century!Mendel’s!Work!on!Transmission!of!Traits!• Pea!plants;!decade!long!experiment;!Augustinian!monk.!• Showed!that!traits!are!passed!from!parents!to!offspring!in!predictable!ways!• Genetics:!branch!of!biology!concerned!with!heredity!and!variation!!Chromosome!Theory!of!Inheritance:!Mendel!and!Meiosis!• 20!years!after!Mendel’s!work,!we!discovered!chromosomes.!• Diploid!number!(2n):!number!of!chromosomes;!46!in!humans!• Homologous!chromosomes:!chromosomes!in!diploid!cells!exist!in!pairs!• Haploid!number!(n):!cells!produced!from!meiosis!only!receive!one!chromosome!from!each!pair.!• Mitosis:!chromosomes!copied;!each!daughter!cell!receives!identical!set!of!chromosomes!to!parent.!• Meiosis:!gamete!formation;!cells!receive!one!chromosome!from!each!chromosome!pair.!• Walter!Sutton!and!Theodor!Boveri:!behavior!of!chromosomes!in!meiosis!is!similar!to!behavior!of!genes!in!gamete!formation!noted!by!Mendel.!• Chromosome!theory!of!inheritance:!inherited!traits!controlled!by!genes!on!chromosomes!that!are!transmitted!through!gametes;!genetic!continuity!throughout!generations.!!Genetic!Variation!• Drosophila#melanogaster:!fruit!fly!used!for!studying!inheritance!of!traits.!• Mutation:!heritable!change!in!DNA!sequence;!source!of!genetic!variation!• Allele:!alternative!forms!of!a!gene!• Phenotype:!observable!features,!such!as!eye!color!• Genotype:!set!of!alleles!for!a!given!trait!• Geneticist!can!map!the!location!of!a!gene!on!the!chromosome!using!mutations!!The!Search!for!the!Chemical!Nature!of!Genes:!DNA!or!protein?!• WhiteDeye!mutation!in!fruit!flies!showed!that!he!trait!was!on!a!single!chromosome.!• Proteins!and!DNA!are!major!chemical!components!of!chromosomes!• 1944:!researchers!at!Rockefeller!Institute!showed!that!DNA!carried!genetic!information!in!bacteria;!did!not!convince!many!scientists.!• Further!work!on!viruses!proved!that!DNA,!not!protein,!carried!genetic!information!and!scientists!turned!their!attention!toward!deducing!the!structure.!!PCB3063!Summer!2014!!!3!!1.3 Discovery!of!the!Double!Helix!Structure!of!DNA!and!RNA!• 1953:!James!Watson!and!Francis!Crick!described!structure!of!DNA;!along!with!Maurice!Wilkins!they!received!the!Nobel!Prize!in!1962.!• Each!linear!strand!of!DNA!is!made!up!of!nucleotides:!A!(adenine),!G!(guanine),!T!(thymine)!or!C!(cytosine).!• The!two!strands!of!DNA!are!complements!of!each!other!AT!and!CG!are!pairs.!• RNA!contains!ribose!instead!of!deoxyribose!(in!DNA).!!Gene!Expression!• Phenotype!is!expressed!as!a!result!of!the!order!of!the!nucleotides!in!DNA!through!a!series!of!steps.!• Transcription:!in!eukaryotes,!one!strand!of!DNA!is!used!to!construct!a!complementary!strand!of!RNA.!That!RNA!molecule!moves!to!the!cytoplasm!where!the!mRNA!binds!to!the!ribosome.!• Translation:!the!synthesis!of!proteins!under!the!instruction!of!mRNA.!!• Genetic!code:!!the!information!encoded!in!the!mRNA;!series!of!nucleotide!triplets!called!codons.!• There!are!20!different!amino!acids!found!in!proteins.!• TRNA:!transfer!RNA;!assembles!proteins;!recognize!the!code!in!the!RNA!and!carry!the!correct!amino!acids!to!construct!the!protein!in!translation.!!Proteins!and!Biological!Functions!• Proteins!are!end!product!of!gene!expression!• Diversity!of!life!arises!from!proteins!that!are!long!and!each!position!can!be!one!of!20!amino!acids.!• Enzymes:!biological!catalysts;!largest!category!of!proteins;!allows!cellular!metabolism!to!happen!at!body!temperature!and!lower!activation!energies!• Hemoglobin:!oxygen!binding!molecule!in!red!blood!cells!•
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