Ch02 mitosis and meiosis

C,hapter 2,Mitosis and Meiosis,Maintenance of Genetic Continuity Between Cells and Organisms,Mitosis(,有丝分裂,),Two genetically identical, generally,diploid(,二倍体,),cells (same as parent cell),Meiosis,(,减数分裂,),Reduction division produces,progeny(,后代,),cells,with one-half the genetic content and number of chromosomes as parent cell,Produces,gametes,配子,/,spores,孢子,for sexual reproduction,2.1,Cell,structure,线粒体,细胞质,溶酶体,滑面内质网,游离核糖体,中心体,核糖体,粗面型内质网,质膜,细胞外被,细胞核,核仁,染色质,核膜孔,核膜,高尔基体,Glycocalyx ,laikukeiliks,(,细胞外被的,),多糖,蛋白质复合物,Heterochromatin(,异染色质,):,The heavily staining, late replicating regions of chromosomes that are condensed during the,interphase,of cell cycle.,Euchromatin,(,常染色质,):,Chromatin or chromosomal regions that are lightly staining and are relatively uncoiled during the,interphase,of cell cycle,.,Nucleus,两种染色质的区别,常染色质,异染色质,染色较淡,深,间期解旋,不解旋,遗传功能活跃，含基因,惰性，不含基因，,分布于染色质两臂,着丝粒附近，染色质末端,复制较早,较晚,端粒,异染色质,着丝粒,常染色质,姐妹染色单体,短臂,长臂,2.2,Chromosomes,exist in Homologous Pairs in Diploid Organisms,Chromosome in eukaryotes,petit,Chromosomes differ in size and,morphology,(,形态,),.,Each has a constriction called a,centromere,(,着丝粒,),that is used in segregation during mitosis and meiosis.,中着丝粒染色体,近中着丝粒染色体,近端着丝粒染色体,端着丝粒染色体,Specialized Chromosomes,P,olytene,Chromosomes(,多线染色体,),Polytene,chromosomes are giant chromosomes consisting of many identical,strands,T,he,bands of,polytene,chromosomes were usually concerned as the visible manifestation of genes.,中文定义：双翅目昆虫,的,幼虫唾腺细胞,，多条染色质（,500,1000,条染色线）重叠成类似染色体状结构。,Specialized Chromosomes,Lampbrush,Chromosomes(,灯刷染色体,),Lampbrush,chromosomes are meiotic chromosomes characterized by extended lateral loops, which reach maximum extension during,diplotene,（,双线期,),.,中文定义：两栖类未成熟的卵母细胞第一次减数分裂停留在双线期的染色体。是,RNA,合成的活跃场所。一个侧环是一个转录单位。,Bacterial,Chromosome,细菌染色体,The chromosomes of bacteria are much less complicated than,eukaryotes,真核生物,do.,They,usually,consist of a,double stranded,nucleic acid molecular, exist as,circular form, and are compacted into a structure sometimes referred to as the,nucleoid(,类核,),.,Viral,（病毒的）,Chromosome,Viral chromosomes chemically may contain either,DNA,or,RNA,.,The DNA containing viral chromosomes may be either of linear shape or circular shape.,The RNA containing viral chromosomes are composed of a linear, single-stranded RNA molecule and occur in some animal viruses, most plant viruses and some bacteriophages.,一些生物的,染色体,数目,Homologous,chromosomes,haploidy, and,diploidy,Homologous chromosomes(,同源染色体,):,Chromosomes,that,pair(,synapse,联会,),in meiosis and have the same genetic loci and structure.,One,member of each pair is,derived,from,the,materal,parent,and,the other,is,derived,from,the,pateral,parent,.,Sex-determining chromosomes are important exception to the concept of,homologous pairs of chromosomes.,Haploid(,单倍体,):,a cell or organism(,生物体,),containing the set of chromosomes normally found in gametes.,The total set of genes contained in a haploid set of chromosomes constitutes the genome of the species.,Diploid(,二倍体,):,a cell or organism with two complete sets of homologous chromosomes.,Diploid cells are produced by haploid (N) gametes that fuse to form a,zygote,(,受精卵,),. The zygote then undergoes development, forming a new individual.,G,enome,(,基因组,)(P21):the,total collection of genes/genetic material of an organism (haploid,set.,Locus/loci(,基因座,),(P21),:,the site or place on a chromosome where a particular gene is,located.,allele (,等位基因,),(P21),:,one of the possible states of a,gene.,k,aryotype,(,核型,),(P21),:,the chromosome complement of a cell or an individual.,染色体的核型,(karyotype),一个物种的一组染色体所具有的特定的染色体的大小，形态和数目。,核型分析,：根据染色体数目、大小和着丝粒位置、臂比、次缢痕、随体等形态特征，对生物核内染色体进行配对、分组、归类、编号、进行分析的过程。,Eg,蚕豆的核型分析,2n=12,， 染色体长度：大,小,臂比：,大,小,带型：同源编号,2.3,Mitosis,Partitions Chromosomes into Dividing Cells,Mitosis is critical to all,eukaryotes,(,真核生物,),as a mechanism to produce new cells,Allows for,a,s,exual,(,无性生殖,),reproduction,Proto,z,oans,(,原生动物,),f,ungi(,菌类,),algae(,藻类,),Partitions chromosomes equally into “daughter” cells,Multicellular eukaryotes begin life as a,zygote,(,受精卵,),Mitosis produces all of the cells required for the adult,form,cytokinesis,Cell growth,DNA replication:,Chromosomes,duplicate,Cell prepares,to divide,chromosome,copies,separate,Cytoplasm,divides,Cell division,composed,of:,1,、,Karyoki,n,esis(,核分裂,)(P22),:,process of nuclear division (division of genetic,material).,2,、,Cytoki,n,esis(,胞质分裂,)(P22),:,process of dividing cytoplasm/cell.,Interphase,（,间期）,C,omposed of:,(1) Gap 1 (G1) when the cell prepares for chromosome replication,.,(2) Synthesis (S) when DNA replicates and new chromosomes are formed.,(3) Gap 2 (G2) when the cell prepares for mitosis and cell division.,Relative time in each phase varies among cell types, with duration of,G1,generally the deciding factor. Some cells exit G1 and enter a nondividing state called,G0,.,Interphase chromosomes are elongated and hard to see with light microscopy. Sister chromatids are held together by replicated but unseparated centromeres.,Mitosis,stages,Mitosis is a continuous process, but geneticists divide it into,four,distinguishable stages,:,P,rophase,(,前期,),M,etaphase,(,中期,),A,naphase,(,后期,),T,elophase,(,末期,),动粒,前中期,i. The mitotic,spindle,（纺锤 体）,composed of,microtubules,（,微管 ）,made,of,tubulins,（,微管蛋白 ）,begins to form.,ii. The,nu,cl,eoli,（,核仁，,nucleolus,的复数,）,in the nucleus cease to be discrete areas.,iii. The nuclear envelope breaks down.,iv.,Kinetochores,（动粒）,form on the,centromeres,(,着丝粒,),and become attached to,kinetochore,microtubules,（动粒微管）,.,Prophase,(,前期,),is,characterized by chromosomes condensing to a form visible by light,microscopy,Metaphase,(,中期,),begins when the nuclear envelope has completely disappeared.,i. The,ki,n,etochore,（,动粒）,micro,t,ubules,orient the chromosomes with their,centromeres,in a plane between the spindle poles, the metaphase plate.,ii.,T,he,chromosomes,reach,a highly condensed state.,A,naphase,(,后期,),begins,when the,centromeres,of the sister,chromatids,separate.,i. The,chromatids,separate (disjunction) and daughter chromosomes move toward opposite poles by,ki,n,etochore,microtubules.,ii. Shape of the chromosomes moving toward the poles is defined by their,centromere,locations.,iii.,Cytoki,n,esis,(,胞质分裂,),usually begins near the end of anaphase.,T,elophase,(,末期,),is,when migration of daughter chromosomes is completed.,i. Chromosomes begin to uncoil and form,interphase,chromosomes.,ii. Nuclear envelope forms around each chromosome group.,iii. Spindle microtubules disappear.,iv. Nu,cl,eoli reform.,v. Nuclear division is complete.,Cytoki,n,esis,(,胞质分裂,),（,P25),Cytokinesis,is division of the cytoplasm,compart,m,entalizing,（,划分 ）,the new nuclei into separate daughter cells,.,In animal cells,cytokinesis,begins with a constriction in the center of the cell, which develops until two new cells are produced.,Most plant cells form a cell plate (membrane and wall) between the two nuclei, resulting in two progeny cells,Animal Cell,Cytokinesis,Microfilaments contract,Cleavage furrow,微丝,卵裂沟,cell wall,former spindle equator,cell plate,Plant Cell,Cytokinesis,细胞板,有丝分裂的特点,：染色体复制,1,次，细胞分裂,1,次，子细胞与母细胞一样。,有丝分裂的意义：,1.,保证了细胞上下代之间遗传物质的稳定性和连续性。,2.,维持个体的正常生长和发育,分裂 数量,个体发育 细胞,分化 种类,前期：,染色质细长如丝、开始浓缩，核膜、核仁变淡。,中期：,染色体，着丝粒排列，纺锤体形成，观察最佳。,后期：,着丝粒一分为二。,末期：,核仁出现,赤道面细胞板,两极分离,子细胞形成。,染色体数目未变,小结：有丝分裂过程,2.4,Meiosis,&,Sexual,reproduction,(,减数分裂,),(,有性生殖,),An overview of,m,eiosis,Reduction,division,Reduces the chromosome number from diploid to haploid,Formation of,germ,cells,(,生殖细胞,),and,spores,(,孢子,).,Involves 2 cell divisions,Meiosis I,Meiosis II,Unlike mitosis,crossing,over,(,交换，交叉,),between homologous chromosomes occurs,Necessary to allow for sexual reproduction by diploid organisms,Reduces the chromosome number from diploid (2n) to haploid (n) in,germ cells,生殖细胞,and spores,孢子,Produces tremendous genetic diversity,In meiosis, homologous,chromosomes,form,pairs,they,synapse,(,联会,).,And each,synapsed,structure,is,initially called a,bivalent,(,二价体,),which,eventually gives,rise,to a unit,the,tetrad,(,四分体,),consisting,of four,chromatids,.,In,meiosis I, described as a,reductional,division,conmponents,of each tetrad separate and yield two,Dyads,(,二分体,),.,In,meiosis II, described as a,equational,division, each dyad splits into two,Monads,(,单分体,),of one chromosome each.,F,our,haploid cells,are,usually produced. Each has one chromosome from each homologous,pair.,Prophase I,Lepto,n,ema,（,细线期,）,Zygo,n,ema,（,偶线期）,Pachy,n,ema,（,粗线期 ）,Diplo,n,ema,（,双线期 ）,Diaki,n,esis,（,终变期、浓缩期）,Meiosis I,is when the chromosome information is reduced from diploid,to,haploid,. It has four stages:,Metaphase I,Anaphase I,Telophase I,Leptonema,(,细线期,),is when chromosomes begin to coil, committing the cell to the meiotic process.,A process called,h,omolog,y search, which precedes the initial pairing of,homologs, begins,during th,is,stage.,细线期特点：条染色体有两条单体,;,染色质细长如丝,In,zygonema,(,偶线期,),t,he,synaptonemal,complex,（,联会复合体）,begins to form and,synapsis,occurs.,Synapsis,is referred to,a tight association between homologous,chromosomes,.,偶线期：同源染色体配对（联会）；联会复合体；二价体,-,四条单体,In,p,achynema,(,粗线期,),crossing-over,(,交换,), which can result in genetic exchange between members of each,homolog(,nonsister chromatids,非姐妹染色单体,),occurs.,粗线期,：非姊妹染色单体间交换重组,Diplonema,(,双线期,),is when chromosomes begin to move apart, and,chi,a,smata,(,交叉,),(singular is,chiasma,) formed by crossing-over become,visible,.,双线期：联会的同源染色体相互排斥、开始分离，但在交叉点,(chiasma),上还保持着联系。交叉结向末端移动并逐渐减少，称为交叉端化。,Diakinesis,(,终变期,),involves breakdown of the,nucleoli,（,核仁 ）,and nuclear envelope, and assembly of the spindle.,In,addition,the,chromosomes,pull farther apart and a process called,terminalization,（,末端化 ）,is completed during this,stage,.,终变期,：交叉完全端化,1,2,3,4,交换,Metaphase,I,(,中期,I,),T,he,nuclear envelope completely broken down,.,Chromosomes maximally thickened,Nonsister,chromatids,associated at terminal,chiasma,(,交叉,),O,nly,bivalents,(pairs of,homologs,) aligned at the,equatorial,plane,（赤道板）,T,he,spindle completely formed, and microtubules attached to,kinetochores,（,动粒 ）,中期,I,的主要特点是染色体排列在赤道面上。,A,naphase,I,(,后期,I,),Anaphase I is when bivalents separate, with chromosomes of each homologous pair disjoining. Resulting,dyads,(,二分体,),migrate toward opposite poles, where new nuclei will form. This migration assumes that:,i.,Centromeres,(,着丝粒,),derived from each parent will migrate randomly toward each pole.,ii. Each pole will receive a haploid complement of replicated,centromeres,with associated chromosomes.,iii.,Sister,chromatids,(,姊妹染色单体,),will remain attached to each other (the major difference from,mitosis).,后期,I,：同源染色体彼此分离，分别向两极移动。染色体数目减半。,同源染色体随机分向两极，使母本和父本染色体重所组合，产生基因组的变异。,T,elophase I,(,末期,I,),Telophase I,has dyads completing migration to the poles, and usually formation of a nuclear envelope around each haploid grouping.,Cytokinesis,(,胞质分裂,),follows in most species, forming two haploid cells.,But,cells may either go directly to meiosis II or have short interphase (but no further DNA replication),末期,I,：染色体到达两极后，解旋为细丝状、核膜重建、核仁形成，同时进行胞质分裂。,Meiosis,II,Prophase II,involves chromosome,condensation.,每条染色体含,2,条姊妹染色单体,染色体数是,n,。,Metaphase II,includes spindle formation, with,centromeres,lining up on the,equator.,染色体着丝粒排列在赤道板上。,Anaphase II,involves splitting of the,centromeres, with chromosomes pulled to opposite,poles.,着丝粒纵裂,姊妹染色单体向两极移动。,Telophase,II,takes place as a nuclear envelope forms around each set of,chromosomes.,核膜重新形成,。,Cytokinesis,usually takes place, and chromosomes become elongated and invisible with light,microscopy.,减数分裂的特点：,染色体复制,1,次，细胞连续分裂,2,次，,1,次分裂,1,个细胞形成,4,个细胞，子细胞染色体是母细胞一半。,减数分裂的意义,1,.,遗传：,保证了物种的相对稳定性：,2.,变异,:,为子代的变异提供了物质基础，有利于进化,：,后期,I,同源染色体的成员移向两极是随机的，非同源染色体的组合是自由的。,1,）同源染色体并不完全相同,粗线期交换；,2,）后期,I,，同源染色体彼此分离时， 非同源染色体自由组合分配到子细胞中时，有,2,n,种组合方式。,Mitosis,Members,of homologous pairs passed on autonomously,Meiosis,Homologous chromosomes pair to form tetrads,Meiosis I is a reduction division,(chromosome number,is halved),Meiosis,II is an,equational,division,(chromosome,number remains,unchanged),2.5 Spermatogenesis,(,精子发生,),&,Oogenesis,(,卵子发生,),Spermato,g,onium,(,精原细胞,),Diploid,Enlarges to form,Primary,sp,ermatocyte,(,初级精母细胞,),Meiosis I to form,Secondary,spermatocyte,(,次级精母细胞,),Haploid/but dyads,Meiosis II forms,Spermatids,(,精细胞,),Differentiation,Spermatogenesis,(,精子发生,),Oogenesis,Oogonium,(,卵原细胞,),Diploid,Enlarges to form,Primary,oocyte,(,初级卵母细胞,),Meiosis I to form,Secondary oocyte,(,次级卵母细胞,),and,1,st,polar,body,（第一,极体）,Haploid/but dyads,Meiosis II forms,Ootid,（卵子）,/,2,nd,polar,body,（第二,极体）,Diffentiation,皮层粒,Alternation of generations of plants:,Gametophyte,（配子体）,Sporophyte,（孢子体）,雄蕊,孢子体,雌蕊,小孢子母细胞,大孢子母细胞,管核,生殖核,助细胞,反足细胞,胚核,胚乳核,双受精,糊粉粒,果皮,两个极核,P95,双受精：一精核,+,卵细胞合子；,一精核,+,两极核胚乳,种子嵌合体,嵌合体：遗传来源或组成不同的组织、器官或者个体。,种皮,2n,：来源于母本的珠被,种子,胚乳,3n,：,2n,母本；,n,父本,胚 ,2n,：,n,母本；,n,父本,植物的双受精,