专业英语(遗传学的基础).ppt

Lesson four Foundation of genetics 遗传学的基础,湖北医药学院附属人民医院生殖医学中心 江胜芳（Tel,孟德尔生平介绍,孟德尔，Gregor Johann Mendel（1822.7.20-1884.1.6），出生于奥地利西里西亚海因策道夫村一个贫寒的农民家庭，父母都是园艺家 毕业院校：奥尔米茨大学、维也纳大学 圣托马斯修道院修道士，现代遗传学之父 主要成就：发现遗传定律,背景知识,泛生论Vs种质学说 显性基因Vs隐性基因 纯合子Vs杂合子 基因型Vs表现型 分离规律Vs自由组合规律,泛生论,生物体各部分的细胞都带有特定的自身繁殖的粒子，称为“微芽”或“泛子” 这种粒子可传递给子代，使它们呈现亲代的特征 环境的改变可使“微芽”或“泛子”的性质发生变化，因而亲代的获得性状可传给子代。,种质学说,德国生物学家魏斯曼1892年提出的有关遗传物质的学说 多细胞的生物体可截然地区分为种质和体质两部分 种质是遗传物质，存留在生殖细胞的染色体上，种质可以发育为新个体的体质，只有种质才能世代传递，连续不绝 体质可以通过生长和发育而形成为新个体的各个组织和器官，但它不能产生种质 体质获得的变异性状不能遗传给后代 体质随个体死亡而消失,显性基因Vs隐性基因,显性基因(dominant gene)：用来形容一种等位基因，无论在同质还是异质的情况，都会影响表现型。 隐性基因(recessive gene)：在纯合状态时能在表型上显示出来，但在杂合状态时就不能显示出来的基因。,纯合子Vs杂合子,纯合子：同一位点上的两个等位基因相同的基因型个体， 如AA, aa 。 杂合子：同一位点上的两个等位基因不相同的基因型个体，如 Aa 。杂合子间交配所生后代会出现性状的分离。,基因型Vs表现型,基因型：基因型又称遗传型，即控制性状的基因组合类型。一般是指生物体被研究的性状的有关基因的组成，它是性状表现的内在因素，一般用符号来表示，如豌豆高茎的基因型可用DD或Dd表示；矮茎可用dd表示。 表现型：简称表型。具有特定基因型的个体，在一定环境条件下，所表现出来的性状特征的总和。但在杂交试验中，表现型仅指与分离有关的性状，如豌豆的圆和皱、果蝇的长翅和残翅等。,分离规律Vs自由组合规律,分离规律：决定某一性状的成对遗传因子，在减数分裂过程中，彼此分离，互不干扰，使得配子中只具有成对遗传因子中的一个，从而产生数目相等的、两种类型的配子，且独立地遗传给后代 自由组合规律：具有两对（或更多对）相对性状的亲本进行杂交，在F1产生配子时，在等位基因分离的同时，非同源染色体上的非等位基因表现为自由组合,YR,Yr,YR,Yr,yR,yr,Yy Rr,YR,yr,YY RR,yy rr,yr,yR,Yr yR,Yr yr,yR yr,yR yR,yR Yr,yr yR,yr Yr,yR YR,yr YR,yr yr,YR YR,YR Yr,Yr YR,Yr Yr,YR yR,YR yr,YR,yr,Y:黄色 y:绿色 R:圆粒 r:皱粒,P,F1,F2,1.Early theories of inheritance 遗传学的早期理论,Early ideas of inheritance /included /Hippocrates theory of pangenesis pndenisis / and /August Weismanns vaism:n germ d:m plasm plzm theory. 遗传学的早期理论包括希波克拉底（古希腊名医）的泛生说和奥古斯特-魏斯曼(德国生物学家)的种质理论。,Based on experiments with mice, Weismann proposed that/ hereditary information in gametes gmi:t /transmitted/ traits /to progeny prdini . 基于小鼠实验，魏斯曼提出配子中的遗传信息可以将遗传特性传递给后代。,Both of these early views/ incorporated ink:preitid / the blending blendi theory: they held that /heritableheritbl traits of the two parents /blend, so that /the distinct characteristics krktristik of each /are lost /in offspring. 这两个早期观点组合起来形成混合理论：两个亲本的遗传特征混合，那么每个亲本的不同特征就在子代中丧失了。,2. Gregor Mendel and the Birth of Genetics 格里戈-孟德尔和遗传学的诞生,Gregor Mendel, an Augustinian :gstinin monk mk in the monastery mnstri at Brunn, Austria, is known as the “father of genetics”. 格里戈 -孟德尔，是奥地利布鲁恩的修道院的一名奥古斯丁修道士，是众所周知的遗传学之父。,Having been exposed to/ theories of the particular nature of matter /while a university student /and having a background in mathematics, Mendel carried out /a series of/ carefully planned experiments /that demonstrated the particulate ptikjulit nature of heredity hrediti . 孟德尔曾在读大学时学习（接触）了物质的粒子属性,并且，孟德尔有数学基础，于是，他进行了一系列周密安排的实验来证实遗传的颗粒属性。,His revolutionary ideas /were neither understood /nor accepted /until many years after Mendel died. 直到他去世后若干年，他的创新性的理论才被理解和接受。,3. Mendels Classic Experiments 孟德尔的经典实验,Mendel studied genetics /through plant-breeding experiments /with the garden pea, a plant/ that is self-fertilizing /and breeds bri:d true (each offspring is identical to the parent in the trait of interest). 孟德尔通过豌豆育种实验来研究遗传学，豌豆是自花授粉的，并且是真实遗传的(每个子代和亲本的遗传特征是一样的)。,To test the blending theory, he focused /his research /on seven distinct characters. 为验证混合理论，他的研究主要集中在7个不同的特征上。,Each of these characters, such as seed color and plant height, present only two, clear-cut possibilities. 每个特征如种子颜色，植株高度等，都只有两个明确的可能性。,He also recorded/ the type and number/ of all progeny/ produced from each pair of parent pea plants, and followed the results/ of each cross for two generations. 他也记录了来自于每一对亲本的所有子代的类型和数量，和两个子代杂交的结果。,For each of the characters /he studied, Mendel found that /one trait was dominant dminnt /while the other was recessive risesiv . 对于他研究的每个特征而言，孟德尔发现一个特征是显性的,那么另一个就是隐性的。 In the second filial filjl (F2) generation, the ratio /of dominant to recessive /was 3:1. 在子2代中, 显性与隐性比为31。,Mendel deduced that/ this results was possible /only if /each individual possesses only two hereditary units, one from each parent. 孟德尔推论:只有在每个个体仅拥有两个遗传单元，并每个单元来自一个亲本时，实验结果才成立。,The units /Mendel hypothesized haipisaiz/ are today known as /alleles li:l , alternative forms of genes. 孟德尔假设的遗传单元就是今天共识的等位基因,基因的两种形式。 Genes are the basic units of heredity. 基因是遗传的基本单元.,An organism /that inherits /identical alleles for a trait/ from each parent/ is said to be homozygous /hmzaigs for that trait; if different alleles for a trait /are inherited, the organism is heterozygous hetruzaigs for that trait. 从亲本遗传而来的是一个特征的两个相同的等位基因的个体被认为是纯合的。反之,遗传而来的是两个不同的等位基因的个体，就是杂合的。,When an organism/ is heterozygous /for a trait, the resulting phenotype fi:ntaip/ for that trait /expresses only the dominant allele. 对某一个特征而言,当个体是杂合时，它的表型仅由显性基因决定。,Thus,the organisms phenotype-its physical appearance and properties-/differs from /its genotype dentaip , which may include /both a dominant and a recessive allele. / 因此，生物的表型与基因型是不同的,表型是个体的物理特征和品质, 而基因型包括一个显性基因和一个隐性基因。,A pictorial representation of/ all possible combination of a genetic cross/ is known as a Punnett square. 遗传杂交的所有可能的组合图表被称为旁纳特方格。,Punnett square：a method used to determine the probabilities of combination in a zygote zaigut .,The results /of Mendels experiments/ on dominant and recessive inheritance / led to /Mendels first law: the law of segregation. 基于显性和隐性遗传的实验结果，孟德尔提出了分离定律。,This law states that/ for a given trait /an organism/ inherits /one allele /from each parent. 该定律认为:对一个给定的特征而言,个体从每个亲本获得一个等位基因。 Together these alleles /form /the allele pair. 这些等位基因一起形成等位基因对。,When gametes gmi:t are formed /during meiosis, the two alleles /become separated (halving of chromosome number). 减数分裂期形成配子时两个等位基因分离(染色体数目的减半)。,To gain evidence for his theory /Mendel performed test crosses, mating plants /of unknown genotype/ to plants /that were homozygous hmzaigus recessive risesiv /for the trait of interest. 为验证此理论，他做了测交实验，即基因型未知的植物个体与纯合隐性的个体杂交。 Test cross：a cross between a heterozygote of unknown genotype and an individual homozygous for the recessive genes in question.,The ratio/ of dominant phenotypes (if any)/ in the progeny /makes clear/ whether the unknown genotype is heterozygous, homozygous dominant, or homozygous recessive. 子代显性表型的比例可以明确测得未知的基因型是杂合基因、纯合显性基因或是纯合隐性。,4. Mendels ideas and the law of independent assortment 孟德尔的设想及自由组合定律,Mendel also performed/ dihybrid daihaibrid crosses, which enabled him /to consider /how two traits are inherited /relative to one another. 孟德尔也进行了双因子杂交试验，该实验说明了两个特征相互间是如何遗传的。,This work led to/ the law of independent assortment, which states that/ the alleles of genes governing different characters/ are inherited /independently. 试验结果产生了自由组合定律，即控制不同性状的等位基因是独立遗传的。,YR,Yr,YR,Yr,yR,yr,Yy Rr,YR,yr,YY RR,yy rr,yr,yR,Yr yR,Yr yr,yR yr,yR yR,yR Yr,yr yR,yr Yr,yR YR,yr YR,yr yr,YR YR,YR Yr,Yr YR,Yr Yr,YR yR,YR yr,YR,yr,Y:黄色 y:绿色 R:圆粒 r:皱粒,P,F1,F2,An apparent exception to Mendels law /is incomplete dominance, a phenomenon/ in which /offspring of a cross /exhibit a phenotype/ that is intermediate between those of the parents. 孟德尔定律的一个特例是，不完全显性，即杂交后子代的表型是父母亲本的中间类型。,However, incomplete dominance /reflects/ the fact /that both alleles for the trait /in question /exert /an effect /on the phenotype. 但是，不完全显性说明了两个等位基因可能对表型有影响。,The alleles themselves remain separate. 等位基因本身仍然是分离的。 Mendel presented his ideas in 1866 in a scientific paper published by the Brunn Society for Natural History. 1866年，孟德尔将其想法发表在由布鲁恩自然历史学会出版的科学论文上。,Unfortunately, the meaning of his research was not understood by other scientists of the day. 不幸的是，他的研究没被当时科学家所接受。 His work was rediscovered in 1900 by Carl Correns and Hugo de Vries. 在1900年，他的著作再次被Carl Correns and Hugo de Vries（科伦斯和德弗里斯）发现。,5. Chromosomes and Mendelian Genetics 染色体和孟德尔遗传学,Soon after Mendels work was rediscovered, Walter Sutton and T