FoundationsofGeneticsGYQLesson4FoundationsofGenetics

EarlytheoriesofinheritanceGregorMendelandtheBirthofGeneticsMendel’sclassicexperimentsMendel’sideasandthelawofindependentassortmentChromosomesandMendelianGeneticsAllele:等位基因

alternativeformsofageneforaparticularcharacteristic(e.g.attachedearlobe([????l??b]耳垂)genesandfreeearlobegenesarealternativeallelesforearshape)

nonallelicgenes:非等位基因dihybridcross:雙因子雜種雜交

AaBbXAaBb

test

cross：

測(cè)交F1Xaa確定F1是純合子還是雜合子

acrossbetweenaheterozygote(異質(zhì)結(jié)合體)ofunknowngenotypeandanindividualhomozygous(同型的)fortherecessivegenesinquestion

Dominant:顯性的dominance

thememberofapairofallelesthatshowsitseffectinthephenotypewhateverotheralleleispresent.

recessive:隱性的recessiveness

thememberofapairofallelesthatdoesnotshowsitseffectinthepresenceofanyotherallelicpartner.

Genotype:基因型

thecatalogofgenesofanorganism,whetherornotthesegenesareexpressed.

Karyotype:核型，染色體組型

phenotype:表現(xiàn)型

thephysical,chemical,andpsychological(心理的)expressionofgenespossessedbyanorganism.Germ(種子,胚)plasmtheory:種質(zhì)論

asubstancethoughttobetransmittedinthegametes(配子,germcells)inanunchangedformfromgenerationtogeneration.

Thegermplasmwasbelievedtobeunaffectedbytheenvironmentandtogiverisetothebodycells.

德國(guó)生物學(xué)家A.魏斯曼1892年提出的有關(guān)遺傳物質(zhì)的學(xué)說(shuō)，認(rèn)為多細(xì)胞的生物體可截然地區(qū)分為種質(zhì)和體質(zhì)兩部分。

種質(zhì)是親代傳遞給后代的遺傳物質(zhì)，存留在生殖細(xì)胞的染色體上,種質(zhì)可以發(fā)育為新個(gè)體的體質(zhì),但有一部分仍保持原來(lái)的狀態(tài)作為后代發(fā)育的基礎(chǔ)，體質(zhì)可以通過(guò)生長(zhǎng)和發(fā)育而形成為新個(gè)體的各個(gè)組織和器官，但它不能產(chǎn)生種質(zhì)。體質(zhì)受環(huán)境影響而獲得的變異性狀也不能遺傳給后代。

體質(zhì)隨個(gè)體死亡而消失；只有種質(zhì)才能世代傳遞，連續(xù)不絕。

所以這一學(xué)說(shuō)又稱為種質(zhì)連續(xù)學(xué)說(shuō)。為后來(lái)T.H.摩爾根開(kāi)創(chuàng)的細(xì)胞遺傳學(xué)和對(duì)遺傳物質(zhì)的深入探索奠定了理論基礎(chǔ)。Homozygous:純合的

adiploidorganismthathastwoidenticalallelesforparticularcharacteristic

heterozygous:雜合的

adiploidorganismthathastwodifferentallelicformsofaparticulargene.Incompletedominance:不完全顯性

theconditioninwhichtwoallelicgeneshaveadifferenteffectwhentheyaretogetherasaheterozygoteinadiploidcellthaneitherofthemhaveinthehomozygousstate.

Codominance:共顯性

雜合體中一對(duì)等位基因的作用都表現(xiàn)Lawofindependentassortment:

獨(dú)立分配定律

membersofonegenepairwillseparatefromeachotherindependentlyofthemembersofothergenepairs.Lawofsegregation:分離定律

whengametesareformedbyadiploidorganism,theallelesthatcontrolatrait

separatefromoneanotherintodifferentgametes,retainingtheirindividuality.Nondisjunction:不分離

thefailureofseparationofpairedchromosomesatmetaphase,resultinginonedaughterreceivingbothandtheotherdaughtercellnoneofthechromosomesinquestion.

Nondisjunctioncanoccurduringameioticormitoticdivision.Pangenesis:泛生論，泛生說(shuō)

thetheoryofheredity

postulating(假設(shè))

that

germs,humours(體液),oressencesmigratefromindividualbodycellstothesexorgansandcontributetothegametes.

Humour[?hju:m?]

n.幽默，風(fēng)趣（等于humor）

體液（舊時(shí)認(rèn)為存在人體內(nèi)，有四種，可影響健康和性格）Punnettsquare:龐納特方格

amethodusedtodeterminetheprobabilitiesofcombinationinazygote(受精卵)1.EarlytheoriesofinheritanceEarlyideasofinheritanceincludedHippocrates’theoryofpangenesisandAugustWeismann’sgermplasmtheory.Basedonexperimentswithmice,Weismannproposedthathereditaryinformationingametestransmittedtraitstoprogeny.Bothoftheseearlyviewsincorporatedtheblendingtheory:theyheldthatheritabletraitsofthetwoparentsblend,sothatthedistinctcharacteristicsofeacharelostinoffspring.Gamete[‘ɡ?mi?t]n.配子progeny(['pr?d??ni]n.子孫希波克拉底(HippokratesofKos，約前460——前377)

被西方尊為“醫(yī)學(xué)之父”的古希臘著名醫(yī)生，歐洲醫(yī)學(xué)奠基人，古希臘醫(yī)師，西方醫(yī)學(xué)奠基人。提出“體液(humours)學(xué)說(shuō)”，認(rèn)為：

人體由血液(blood)、粘液(phlegm)、黃膽(yellowbile)和黑膽(blackbile)四種體液組成，這四種體液的不同配合使人們有不同的體質(zhì)。

他把疾病看作是發(fā)展著的現(xiàn)象，認(rèn)為醫(yī)師所應(yīng)醫(yī)治的不僅是病而是病人；從而改變了當(dāng)時(shí)醫(yī)學(xué)中以巫術(shù)和宗教為根據(jù)的觀念。

主張?jiān)谥委熒献⒁獠∪说膫€(gè)性特征、環(huán)境因素和生活方式對(duì)患病的影響。重視衛(wèi)生飲食療法，但也不忽視藥物治療，尤其注意對(duì)癥治療和預(yù)后。他對(duì)骨骼、關(guān)節(jié)、肌肉等都很有研究。他的醫(yī)學(xué)觀點(diǎn)對(duì)以后西方醫(yī)學(xué)的發(fā)展有巨大影響。August

Weismann，(1834～1914)

德國(guó)動(dòng)物學(xué)家。1834年1月17日生于法蘭克福，1914年11月5日卒于弗賴堡。1856年入格丁根大學(xué)學(xué)醫(yī)。先后在巴登和奧地利當(dāng)過(guò)軍醫(yī)和私人開(kāi)業(yè)醫(yī)生。1861年在吉森大學(xué)從師于德國(guó)動(dòng)物學(xué)家K.G.洛伊卡爾特，學(xué)習(xí)動(dòng)物發(fā)生學(xué)及形態(tài)學(xué)，1863年完成了關(guān)于雙翅目昆蟲(chóng)變態(tài)的論文。1866年擔(dān)任弗賴堡大學(xué)醫(yī)學(xué)系動(dòng)物學(xué)和比較解剖學(xué)副教授，1868年在該校創(chuàng)辦動(dòng)物研究所，任第一任所長(zhǎng)，1871年升任教授。60年代中期以后因眼疾不得不終止顯微鏡下的研究而轉(zhuǎn)向遺傳、發(fā)生和進(jìn)化問(wèn)題的理論探討。他講授達(dá)爾文進(jìn)化論多年，直至1912年退休。

2.GregorMendelandtheBirthofGeneticsGregorMendel,anAugustinianmonkinthemonasteryatBrunn,Austria,isknownasthe“fatherofgenetics.”Havingbeenexposedtotheoriesoftheparticulatenatureofmatterwhileauniversitystudentandhavingabackgroundinmathematics,Mendelcarriedoutaseriesofcarefullyplannedexperimentsthatdemonstratedtheparticulatenatureofheredity.HisrevolutionaryideaswereneitherunderstoodnoraccepteduntilmanyyearsafterMendeldied.Augustinianmonk奧古斯丁修會(huì)的修士Monastery

[?m?n?st?ri]n.修道院，寺院，[復(fù)數(shù)]全體僧侶catholicchurch天主教；天主教會(huì)；天主教堂；大公教會(huì)catholic

[?k?θl?k]adj.包羅萬(wàn)象的；廣泛的普遍的；包容一切的particulatenatureofmatter物質(zhì)的粒子屬性魔鬼家門口開(kāi)分店孟德?tīng)?822年出生在海因珍多弗鎮(zhèn)，1843年他進(jìn)入奧地利布魯恩一家?jiàn)W古斯都修道院。1847年他被任命為牧師。從1851年到1853年在維也納大學(xué)學(xué)習(xí)數(shù)學(xué)和自然科學(xué)。從1854年到1868年在布魯恩現(xiàn)代學(xué)校擔(dān)任自然科學(xué)代課教師。

與此同時(shí)，孟德?tīng)枏?856年起開(kāi)始進(jìn)行他的著名的植物育種實(shí)驗(yàn)。1865年他推導(dǎo)出了著名的遺傳學(xué)定律，他將定律用一篇論文表述出來(lái)，并將論文呈交給布魯恩自然歷史學(xué)會(huì)。1866年他的成果被發(fā)表在該學(xué)會(huì)學(xué)報(bào)上，題目是“植物雜交實(shí)驗(yàn)”。三年后又在同一雜志上發(fā)表了第二篇論文。

1868年孟德?tīng)柋蝗蚊鼮槟翈煏?huì)會(huì)長(zhǎng)，專職行政事務(wù)。

1900年，孟德?tīng)柕难芯砍晒话l(fā)現(xiàn)。3.Mendel’sclassicexperiments-1Mendelstudiedgeneticsthroughplant-breedingexperimentswiththegardenpea,aplantspeciesthatisself-fertilizingandbreedstrue

(eachoffspringisidenticaltotheparentinthetraitofinterest).Totesttheblendingtheory,hefocusedhisresearchonsevendistinctcharacters.BreedBreedtrue(totype):生出后代酷似其雙親

breedinandin:近親交配繁殖

breedoutandout:(動(dòng)物的)異種繁殖

breedout:在人工繁殖過(guò)程中消除(品種的特性)

breedup:養(yǎng)育，教育，養(yǎng)成Mendel’sclassicexperiments-2Eachofthesecharacters,suchasseedcolorandplantheight,presentonlytwo,clear-cutpossibilities.Healsorecordedthetypeandnumberofallprogenyproducedfromeachpairofparentpeaplants,andfollowedtheresultsofeachcrossfortwogenerations.Mendel’sclassicexperiments-3

Foreachofthecharactershestudied,Mendelfoundthatonetraitwasdominantwhiletheotherwasrecessive.Inthesecondfilial(F2)generation,theratioofdominanttorecessivewas3:1.Mendeldeducedthatthisresultwaspossibleonlyifeachindividualpossessesonlytwohereditaryunits,onefromeachparent.Filial[?f?li:?l]adj.子女的adv.子女地Mendel’sclassicexperiments-4TheunitsMendelhypothesizedaretodayknownasalleles,alternativeformsofgenes.Genesarethebasicunitsofheredity.Anorganismthatinheritsidenticalallelesforatraitfromeachparentissaidtobehomozygousforthattrait;ifdifferentallelesforatraitareinherited,theorganismisheterozygousforthattrait.Mendel’sclassicexperiments-5Whenanorganismisheterozygousforatrait,theresultingphenotypeforthattraitexpressesonlythedominantallele.Thus,theorganism’sphenotype(its

physicalappearanceandproperties)differsfromitsgenotype,whichmayincludebothadominantandarecessiveallele.Apictorial(形象化的,生動(dòng)的)representationofallpossiblecombinationsofageneticcrossisknownasaPunnettsquare.Mendel’sclassicexperiments-6TheresultsofMendel’sexperimentsondominantandrecessiveinheritanceledtoMendel’sfirstlaw:thelawofsegregation.Thislawstatesthatforagiventraitanorganisminheritsoneallelefromeachparent.Togethertheseallelesformtheallelepair.Mendel’sclassicexperiments-7Whengametesareformedduringmeiosis,thetwoallelesbecomeseparated(halvingofchromosomenumber).TogainevidenceforhistheoryMendelperformedtestcrosses,mating(使配對(duì),使交配)plantsofunknowngenotypetoplantsthatwerehomozygousrecessiveforthetraitofinterest.Theratioofdominantphenotypes(ifany)intheprogenymakesclearwhethertheunknowngenotypeisheterozygous,homozygousdominant,orhomozygousrecessive.4.Mendel'sIdeasandtheLawofindependentAssortment-1

Mendelalsopreformeddihybridcrosses,whichenabledhimtoconsiderhowtwotraitsareinheritedrelativeoneanother.Thisworkledtothelawofindependentassortment,whichstatesthattheallelesofgenes(governingdifferentcharacters)areinheritedindependently.2AnapparentexceptiontoMendel’slawsisincompletedominance,aphenomenoninwhichoffspringofacrossexhibitaphenotypethatisintermediatebetweenthoseoftheparents.However,incompletedominancereflectsthefactthatbothallelesforthetraitinquestionexertaneffectonthephenotype.Theallelesthemselvesremainseparate.3Mendelpresentedhisideasin1866inascientificpaperpublishedbytheBrunnSocietyforNaturalHistory.Unfortunately,themeaningofhisresearchwasnotunderstoodbyotherscientistsoftheday.Hisworkwasrediscoveredin1900byCarlCorrensandHugodeVries.荷蘭Dutch：HugodeVries

德國(guó)German：CarlErichCorrens

奧地利Austrian：ErichvonTschermak-Sevsenegg5.ChromosomesandMendelianGenetics

S