物理化学老师遗传学lecture one

1、GeneticsYueping CAOPlant Science一.受精的过程(一) 胚珠的结构珠孔珠被卵细胞极核子房壁果皮和种子分别由子房的哪部分发育而来?子房2n子房壁胚珠果皮2n种子果实种子的这些结构又是由胚珠的哪些部位发育而成的?胚珠珠被受精卵受精极核种皮2n胚2n胚乳3n种子Mitosis(有丝分裂) and Meiosis（减数分裂）-The transmission and segregation of genes is determined by the movement of chromosomes through mitosis and meiosis. 基因的传递和分离决

2、定于染色体在有丝分裂和减数分裂中的行为-Mitosis and meiosis only occur in eukaryotes, not present in prokaryotes. 有丝分裂和减数分裂只发生在真核生物Prokaryotic cellsEukaryotic cellsTaxonomic groupBacteriaAll plants, fungi, animals, Protists（原生生物）Sizetypically 5 mNucleusno true nuclear membranenuclear membraneGenetic materialOne circula

3、r molecule of DNA, little proteinLinear molecule of DNA and proteinMitosis and meiosisAbsentPresentDifferences between prokaryotic and eukaryotic cells.真核细胞和原核细胞的区别Eukaryotic cells are of two types:Somatic cells - Any cell in a higher organism that is not a reproductive cell. 2n designates the somat

4、ic chromosome complement. 在高等生物中，除了生殖细胞以外的任何细胞都是体细胞。Examples: cells in the skin, muscle cells, cells in roots.Gametic cells - Reproductive cells. Gametic cells have 1/2 the chromosome complement of somatic cells. Examples: Plants egg and pollen cellsAnimals - egg and sperm cells.Examples of the numb

5、er of chromosome in various species -Most animal somatic cells are _Diploid_. Diploid cells have _2_ sets of chromosomes. Most animal gametic cells are _Haploid_. Haploid cells have _1_ set of chromosomes.-Plant species vary in the number of sets of chromosomes. For example, wheat is a _Hexaploid_ w

6、ith _6_ sets of chromsomes. No. of chromosomesSpecies2n nHumans4623Maize2010Dog7839Indian fern1260630Australian ant21Homologous chromosome（同源染色体）Chromosomes -During mitosis and meiosis, stained chromosomes are visible with a light microscope.在有丝分裂列和减数分裂过程中在光学显微镜下可以看到染色体。 -What are chromosomes compos

7、ed of? 染色体的组成是: DNA, protein and RNAHomologous chromosomes - a pair (in diploids) of essentially identical chromosomes that join and bine DNA in meiosis. 同源染色体是是在减数分裂中可以重新结合在一起的大小形态相同的染色体（体条来自父本，一条来自母本）。 -Humans have 23 pairs of homologous chromosomes. -Chromosomes can be classified based on size an

8、d position of centromere. -Homologous chromosomes are the same size with the exception of the sex chromosomes.Homologous chromosomes-Chromosomes can be classified based on size and position of centromere. -Homologous chromosomes are the same size with the exception of the sex chromosomes.Below are 2

9、 homologous chromosomes. One of these chromosomes would be from this individuals mother and the other from the father. Each homologous chromosome consists of two chromatids. The two chromatid on a chromosome contain identical genetic information. This information was recently replicated during the S

10、 phase of the cell cycle. The two homologous chromosomes would carry alternative alleles for genes. For example, if the individual is heterozygous Aa, one homologous chromosome would carry the A allele and the other chromosome would carry the a allele. Because two chromatids on the same chromosome c

11、arry identical genetic information, both chromatid 1 and 2 would carry the A allele and chromatids 3 and 4 would carry the a allele.Humans have 23 pairs of homologous chromosomesChromatid 2Chromatid 3Chromatid 4Chromatid 1 Chromatid 1Homologous chromosomes of humanMitosis（有丝分裂）Mitosis - Nuclear divi

12、sion with each daughter cells receiving an identical complement of chromosomes. 有丝分裂-核分裂每个子细胞得到一套完整相同的染色体-Mitosis is only a part of the cell cycle. 有丝分裂仅仅是细胞周期的一部分Mitosis（有丝分裂）Mitosis is about 10% of the time of the cell cycle. This is when cell division occurs. During G1, metabolic activity occurs

13、and this stage takes about 25% of the time of the cell cycle. During the S stage, DNA replication occurs and this takes about 40% of the cell cycle time. Metabolic activity occurs during G2 and this stage takes the remaining 25% of the cell cycle.Rapidly dividing eukaryotic cells can go through the

14、entire cycle in 16 hours.Synthesis stage (S)G1 stage MitosisG2 stageCell CycleStages of Mitosis（有丝分裂的时期） Mitosis is a continuous process but it can be divided into four stages（有丝分裂是一个连续的过程，分4个时期）.1. Prophase（前期） Chromosomes condense, nuclear membrane disintegrates.2. Metaphase（中期） - Mitotic spindle

15、forms, chromosomes e attached to the spindle and the chromosomes line up at the central plane.3. Anaphase （后期）- Chromosomes divide longitudinally. One sister chromatid moves to each pole.4. Telophase（末期） - Nuclear membrane reforms, cell division occurs. Stages of Mitosis- Interphase Interphase (间期)

16、Stages of Mitosis- prophase Prophase （前期） . Chromosomes condense, nuclear membrane disintegrates. Stages of Mitosis- Metaphase centromereMetephase（中期） Mitotic spindle forms, chromosomes e attached to the spindle and the chromosomes line up at the central planeStages of Mitosis- Anaphase Anaphase （后期

17、）- Chromosomes divide longitudinally. One sister chromatid moves to each pole.Stages of Mitosis- TelophaseTelophase（末期） - Nuclear membrane reforms, cell division occursMeiosis（减数分裂）Meiosis - The process in gametogenesis or sporogenesis during which one replication of the chromosomes is followed by t

18、wo nuclear divisions to produce four haploid cells. 减数分裂-在配子体形成过程中，染色体复制1次进行2次核分裂，形成4个单倍体细胞。Stages of Meiosis（减数分裂的时期）Prophase I - Chromosomes condense and pair, crossing over between homologous chromosomes occurs（染色体浓缩，同源染色体配对，交换）.Metaphase I - Homologous chromosomes line up at the metaphase plane.

19、 The orientation of the chromosomes is random.同源染色体排列在赤道板两侧，染色体的朝向（被分配到哪极）是随机的Anaphase I - Homologous chromosomes separate. This is referred to as a reductional division.同源染色体分离，即所说的减数分裂。Telophase I - Cells divide.细胞分裂。There is no chromosome replication between meiosis I and meiosis II.减数分裂的第一次分裂和第二

20、次分裂之间没有染色体的复制Prophase II -This is brief as the chromosomes are already condensed from meiosis I.Metaphase II - Chromosomes line up on the metaphase plane.Anaphase II - Chromosomes divide. This is referred to as the equational division.Telophase II - Cells divide.Prophase I - As prophase progresses,

21、chromosomes are pairing and crossing over occurs.Stages of meiosis- Prophase I Chromatid 1 细线期偶线期粗线期？双线期？终线期Metaphase IAnaphase ITelophase I减数分裂的意义形成雌雄配子时染色体减半n，雌雄配子结合形成新的合子，恢复原来的染色体数2n,保持物中的稳定在减数分裂的第一次分裂的前期，部分同源染可以发生交换，另外在后期同源染色体的分到两极是独立的，随机，因此使后代产生变异，给予物种丰富的多样性。Meiosis produces genetic variability

22、 two ways减数分裂产生遗传变异有两个来源 How does this create genetic variability?Independent assortment of chromosomes. （染色体的独立分配） This creates new combinations of genes on chromosomes.(染色体上的基因产生了新组合)Crossing over.（交换：非姊妹染色单体之间） Creates new combinations of chromosomes.新组合的染色体产生How do genes segregate during meiosis

23、?（减数分裂中基因的分离）Genes segregate independently during meiosis. What happens is that if an individual has the genotype AaBb, it will produce the following gametes: 1/4 AB, 1/4 Ab, 1/4 aB, 1/4 ab assuming that A and B are on different chromosomes. The reason we have the four different gametes products is

24、that whether the chromosome carrying A or a are on the left side of the metaphase plate is random. The same is true for B and b. The following are two possible orientations of the chromosomes.如果基因型是AaBb ，减数分裂后将产生下列4种配子：1/4 AB, 1/4 Ab, 1/4 aB, 1/4 ab 。原因如下： 假设A和B在不同的染色体上， 携带A 或 a的染色体在赤道板的左侧或右侧是随机的，因此

25、染色体的分配朝向有两种可能（2），同样携带 B 和 b的染色体也是这样（2）。2*2=4After meiosis II, the gametes AB and ab would be produced from the cell on the left and the gametes Ab and aB would be produced from the cell on the right. 减数分裂后，配子AB 和 ab将产生于细胞的左侧， Ab 和 aB将产生于细胞的右侧。 Differences between Mitosis and Meiosis有丝分裂和减数分裂的区别Mitos

26、isMeiosisCell typeSomaticReproductiveFunctionGrowth and repairGamete formationDaughter cell chromosome no.DiploidHaploidDaughter cell genotypesIdenticalDifferDo homologspair?NoYesDoes crossing over occur?NoYes遗传信息的传递规律和物质基础 孟德尔定律孟德尔实验 用32个品种,观察了7对性状,经8年研究， 发现了2个定律: 独立分配,自由组合定律 创立了“ 遗传学 ”表 11 孟德尔的豌豆杂

27、交实验7对性状的结果 2.84:1277矮787高高植株高植株矮植株3.14:1207顶生651腋生腋生花腋生花顶生2.82:1152黄428绿绿色绿色黄色豆荚2.95:1299瘪882鼓鼓胀膨大缢缩豆荚3.15:1224白705紫紫花 紫花白花3.01:12001绿6022黄黄色黄叶绿色子叶2.96:11850皱5474圆圆形圆形皱缩子叶F2比例 F2F1 豌豆表型 2. 杂种1代的观察： （filial generation 1，F1 ) 确定了 显性（dominate）性状 隐性 (recessive)性状From these experiments, Mendel derived th

28、e following postulates of inheritance:1. Traits are controlled by unit factors that are in pairs. Genetic characters are controlled by unit factors that exist in pairs in individual organisms.形状是由一对遗传因子控制。2. Dominance/Recessiveness. When two unlike unit factors responsible for a single character are

29、 present in a single individual, one unit factor is dominant to the other.两个相似的遗传因子控制一个形状，一个对另一个是显性。3. Segregation. During the formation of gametes, the paired unit factors separate or segregate randomly so that each gamete receives one or the other with equal likelihood.在形成配子的时候，这对遗传因子随机分离，每个配子得到一份

30、。（三）精确验证 创用测交方法对推论加以验证 测交（test cross）： 是指将杂种后代和隐性亲本进行杂交， 回交（back cross）： 是指杂种后代和任一亲本杂交。 第二节 孟德尔定律（Mendels laws） 对一对性状的观察得出了三条规律 （1）F1代的性状一致，通常和一个亲 本相同。得以表现的性状为显性， 未能表现的性状称隐性，此称F1一 致性法则。（2）在杂种F2代中，初始亲代的二种 性状（显性和隐性）都能得到表达；（3）这两性状的比例总为 3：1。一 分离律（Law of segregation） 1分离律的实质 控制性状的一对等位基因在产生配子时 彼此分离，并独立地分配

31、到不同的性细 胞中。 2分离律的意义 具有普遍性 遗传病约有4344种（1988年） 侏儒（先天性软骨发育不全） 显性 裂手裂足 舞蹈病（Huntington） 白化 半乳糖血症 隐性 苯丙酮尿症 全色盲 早老症 自毁容貌综合征 Learning Objectives for Unit 1.1) Understand the following terms: gene, allele, gamete, heterozygous, homozygous, genotype, phenotype, dominant, recessive, hybrid, backcross, testcross,

32、 homologous chromosomes, chromatids, crossing-over, centromere, haploid, diploid, somatic cell, gametic cell2) Know the stages of mitosis and meiosis and understand what happens during each stage.3) Understand the results of mitosis and meiosis.4) Understand the results and implications of independe

33、nt assortment and be able to diagram independent assortment of chromosomes during meiosis.Definitions:Gene - A physical unit of heredity whose existence can be confirmed by allelic variants and which occupies a specific chromosomal locus. Allele - Alternative forms of a given gene.Gamete A specialized reproductive cell with a haplo