Chapter 16 Extranuclear Inheritance.ppt

Chapter16ExtranuclearInheritance 第六章核外遗传 Chapter16ExtranuclearInheritance 16 1Patternsofextranuclearinheritance16 2Organelleheredity16 3Theevolutionaryoriginoforganelles16 4Cytoplasmictransmissionofsymbionts16 5Materialeffectinsnailshellcoiling16 6Insearchofmitochondrial Eve ExtranuclearInheritance Extranuclearinheritanceorcytoplasmicinheritance Inheritancemediatedbyself replicatingcellularfactorslocatedoutsidethenucleus forexample inmitochondriaorchloroplasts Inhigherorganisms extranuclearinheritanceisusuallyindicatedbyuniparentalinheritance whichmeanstransmissionthroughonlyoneparent Genetictransmissionofcytoplasmicfactors suchasmitochondriaorchloroplasts isdeterminedbymaternalandpaternalcontributionsatthetimeoffertilization bymechanismsofeliminationfromthezygote andbytheirregularsortingofcytoplasmicelementsduringcelldivision Uniparentaltransmissionthroughthemotherconstitutesmaternalinheritance uniparentaltransmissionthroughthefatherispaternalinheritance Ahumanspermandegg 奔跑中的精子 精子纵切面 遗传物质储存在精子的头部 排卵过程示意图 排卵过程实景图 卵泡破溃 卵子显露 即将由卵巢排出的卵子 500万个精子同时游向它们的终点 隐蔽在输卵管中的卵子 精子和卵子相遇 进攻 一个精子钻入一个卵子的壳内 此时精子的头已经钻进去了我们还可以看到它的中部和尾部 它就像一个不断旋转的钻头 在尾巴拍打的驱动下 努力进入卵子 一旦有精子进入卵子 其他精子就没有机会了 这个角度看的更为清晰 MaternalinheritanceofhumanmitochondrialDNA 线粒体中所含的DNA 是独立于细胞核染色体外的遗传物质 称线粒体基因组 被称为第 25号染色体 这些基因突变所导致的疾病 称线粒体基因病 随线粒体传递 呈母系遗传 此类疾病也属于单基因病 简称为线粒体病 如帕金森病 型糖尿病 老年性痴呆 心肌病等都是属于线粒体病 线粒体病是母系遗传的 在精子和卵子结合的受精过程中 雌 雄原核分别携带母源和父源的基因组 核基因的结合是对等的 但是 卵子与精子细胞质的结合是远远不对等的 受精卵中的细胞质及其所有的线粒体 绝大部分都是由卵子提供的 精子中的少量线粒体对卵子细胞质内的大量线粒体来说是微不足道的 母亲将她的线粒体DNA传给了她的所有子女 但只有她的女儿又将其线粒体DNA传给下一代 Mitochondrialgeneticdiseases Inheritanceofmyoclonicepilepsywithragged redfiberdisease MERRF inhuman MERRFsyndrome orMyoclonicEpilepsywithRaggedRedFibers 不整红边纤维肌阵挛癫痫 肌阵挛性癫痫伴碎红纤维病 肌阵挛癫痫及褪红纤维病 isamitochondrialdisease Itisextremelyrare withanestimatedprevalenceof1 400 000inEurope andhasvaryingdegreesofexpressivityowingtoheteroplasmy Itinvolvesthefollowingcharacteristics progressivemyoclonicepilepsy RaggedRedFibers clumpsofdiseasedmitochondriaaccumulateinthesubsarcolemmalregionofthemusclefiberandappearas RaggedRedFibers whenmuscleisstainedwithmodifiedG m ritrichromestain shortstature hearingloss lacticacidosis 乳酸性酸中毒 exerciseintolerance poornightvision TheMERRFsyndromeiscausedbyamaternally inheritedmutationatposition8344inthemitochondrialgenomeinover80 ofcases ThispointmutationdisruptsthemitochondrialgenefortRNA Lysandsodisruptssynthesisofproteinsessentialforoxidativephosphorylation Likemanymitochondrialdiseases thereisnocureforMERRFandtreatmentisprimarilysymptomatic HighdosesofCoenzymeQ10andL Carnitinehavebeentriedwithlittlesuccessastherapiesinhopesofimprovingmitochondrialfunction MaternalinheritanceofthemitochondrialdiseaseMDRRF Diseasephenotypesreflecttheratioofmutant to wildtypemtRNAandtherelianceofcelltypeonmitochondrialfunction GenesinhumanmitochondrialDNA MapofthegenesofhumanmitochondrialDNA Maternalinheritanceandmaternaleffect MitochondrialDNAfromratliver MitochondrialDNA MitochondrialDNAintheunicellularorganismEuglenagracilis Organizationofgenesinthechloroplastgenomeoftheliverwort Choroplastgenomeoftheliverwort RNAediting RNAeditingintrypanosomes Humanmitochondriadepartfromthestandardcodeinthethreeprincipalways 36 可编辑 Variationsinthegeneticcodeofmitochondria Trans splicinginwheatmitochondria Leafvariegationcausedbythesegregationofdifferenttypesofchloroplasts Crossesandprogenyphenotypesinvariegatedfour o clockplants 紫茉莉 TwosignificantobservationsfromtheTable16 2 Thegeneticexplanationforthevariegation Heteroplasmy Heteroplasmy Theconditioninwhichtwoormoregeneticallydifferenttypesofmitochondria orotherorganelle arepresentinthesamecellisknownasheteroplasmy Geneticmodelforleafvariegation Chloroplastsortingduringmitosis CellsoftheunicellularalgaChlamydomonasreinhardtii Chlamydomonas 衣藻属 Chlamydomonas 绿藻门 绿藻纲 衣藻科 单细胞藻类 为绿藻中结构最简单的类型 藻体球形或卵形 前端具2条等长的鞭毛 能在水中游动 原生质体中有1大的杯状 少数为H形 星形或片状 的叶绿体 占据了原生质体的大部分空间 叶绿体基部通常埋有1个大的蛋白核 细胞质主要存在在叶绿体的凹入部分 细胞核位于中央 在鞭毛基部的细胞质中 通常有2个伸缩泡 其功能与维持和控制细胞内水分总含量有关 在细胞前端稍偏一侧有红色眼点 为衣藻的感光器官 行无性生殖及有性生殖 无性生殖多在生长旺盛时期进行 原生质体分裂形成2 4 8个或16个带2条鞭毛的游动孢子 母细胞破裂时 游动孢子释放出来 每个游动孢子形成1个新的衣藻 有性生殖多为同配 少数为异配 个别种类为卵式生殖 LifecycleofChlamydomonasreinhardtii Reciprocalcrossesofstrainsofstreptomycin 链霉素 resistance str r versussensitivity str s andmatingtypemt versusmt Reciprocalcrossesofstrainsofstreptomycinresistance str r versussensitivity str s andmatingtypemt versusmt Reciprocalcrossesofstrainsofmxothiazolresistance Mud2 versussensitivity mud2 andmatingtypemt versusmt Normalandmutantpetitecoloniesintheyeast Behaviorofpetitemutationsingeneticcrosses Cytoplasmicmalesterility Cytoplasmicmalesterility Aconditioninwhichaplantdoesnotproducefunctionalpollen butthefemalereproductiveorgansandfertilityarenormal Maternalinheritanceofmalesterilityinmaize Cytoplasmicinheritanceofmalesterilityinmaize Inheritanceofcytoplasmicmalesterility CMS S malesterilitycytoplasm N normalcytoplasmR r nucleargenesforfertilityrestorersS rr N rr S rr S rr sterility S rr N RR S Rr S rr S RR S Rr N RR S RR normal S rr N Rr S Rr S rr S rr S Rr S Rr S rr N Rr S Rr restore 胞质不育基因为S 胞质可育基因为N 核不育基因r 不能恢复不育株育性 核可育基因R 能够恢复不育株育性 三系配套法的一般原理是首先把杂交母本转育成不育系 父本必须是恢复系 不育系A S rr 保持系B N rr 恢复系R S RR 或N RR Theevolutionaryoriginoforganelles Evidencefortheendosymbionttheory ConjugationandautogamyinParamecium Cytoplasmictransmissionofsymbionts maternaleffectAmaternaleffectisasituationwherethephenotypeofanorganismisdeterminednotonlybytheenvironmentitexperiencesanditsgenotype butalsobytheenvironmentandphenotypeofitsmother Ingenetics maternaleffectsoccurwhenanorganismshowsthephenotypeexpectedfromthegenotypeofthemother irrespectiveofitsowngenotype oftenduetothemothersupplyingmRNAorproteinstotheegg Maternaleffectscanalsobecausedbythematernalenvironmentindependentofgenotype sometimescontrollingthesize sex orbehaviouroftheoffspring Ithasbeenproposedthatmaternaleffectsareimportantfortheevolutionofadaptiveresponsestoenvironmentalheterogeneity Maternaleffectinsnailshellcoiling 某个体的表现型并不由其自身的基因型直接决定 而是由母本卵细胞状态决定 母本卵细胞的状态又由母本的基因型决定 ThedirectionofshellcoilinginLimnaeaisdeterminedbytheorientationofthemitoticspindles