Chapter2 The Influence of Heredity on Develop

《Chapter2 The Influence of Heredity on Develop》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、TheInfluenceofHeredityonDevelopmentHeredityandGeneticsHeredityOne’snaturebasedonbiologicaltransmissionoftraitsandcharacteristicsGeneticsFieldwithinthescienceofbiologythatstudiesheredityGeneticsInfluenceourPhysicaltraitsBehavioraltraitsPsychologicalproblemsWhatAreC

2、hromosomesandGenes?ChromosomesFoundincells23pairsGenesSegmentsofDNAwithinchromosomesRegulatedevelopmentoftraitsTransmittedbysinglegeneormaybepolygenic20,000to25,000genesineverycellDoubleHelixofDNAFigure2.1TwoTypesofCellDivisionMitosisCelldivisionbywhichgrowthoccurs

3、StrandsofDNAbreakapart,duplicateandarerebuiltResultisidenticalcopiesofDNAstrandMutationscandevelopthroughoutourlivesTwoTypesofCellDivisionMeiosisCelldivisionbywhichspermandovaareproduced23chromosomepairsdivideResultisanewcellwithonly23chromosomes22pairsareautosomes

4、23rdpairaresexchromosomesTwoTypesofCellDivisionMeiosisCrossingOverThe23PairsofHumanChromosomesFigure2.3HowAreTwinsFormed?MonozygoticTwins(MZ)DerivedfromasinglezygotethathassplitintwoIdenticaltwinsDizygoticTwins(DZ)DerivedfromtwozygotesProbabilityoftwinsincreasesMat

5、ernalageUseoffertilitydrugsHowDoGenesDetermineTraits?TraitsaredeterminedbypairsofgenesEachmemberofpairisanalleleHomozygousBothallelesforatraitarethesameHeterozygousAllelesforatraitaredifferentMendel’sLawsofHeredityAveragingEffectsofbothallelesareshownLawofDominance

6、DominantallelepairedwithrecessivealleleDominantalleleappearsinoffspringTransmissionofDominantandRecessiveTraitsFigure2.4TransmissionofDominantandRecessiveTraitsDominantandRecessiveTraitsCarriersPersonwhohasonedominantandonerecessivegeneChromosomalorgeneticabnormali

7、tiesOccurinautosomesorsexchromosomesMaybecausedbyasinglegeneorcombinationsChromosomalAbnormalities:DownSyndromeCause:extrachromosomeon21stpairProbabilityincreaseswithincreasedageofparentCharacteristicsofchildrenFacialfeaturesCognitiveandphysicaldeficienciesDownSynd

8、romeFigure2.5ChromosomalAbnormalities:Sex-LinkedMostareinfertileMalewithextrasexchromosomeXYY-extraYchromosomeXXY-KlinefeltersyndromeFemalewithab