大學(xué)生物專業(yè)英語lesson-four

1、2022/9/151Lesson fourFoundation of genetics遺傳學(xué)的基礎(chǔ)2022/9/152Early theories of inheritance遺傳學(xué)的早期理論 Early ideas of inheritance included Hippocrates theory of pangenesis pndenisis and August Weismanns vaism:n germ d:m plasm plzm theory. 遺傳學(xué)的早期理論包括希波克拉底（古希臘名醫(yī)）的泛生說和奧古斯特-魏斯曼(德國生物學(xué)家)的種質(zhì)理論。2022/9/153Based on

2、 experiments with mice, Weismann proposed that hereditary information in gametes mtz transmitted traits to progeny prdini . 基于小鼠實驗，魏斯曼提出配子中的遺傳信息可以將遺傳特性傳遞給后代。2022/9/154 Both of these early views incorporated ink:preitid the blending blendi theory: they held that heritableheritbl traits of the two par

3、ents blend, so that the distinct characteristics krktristik of each are lost in offspring. 這兩個早期觀點組合起來形成混合理論：兩個親本的遺傳特征混合,那么每個親本的不同特征就在子代中喪失了.2022/9/155The Mendel Theory - the most popular oneThe Mendel Theory is, by far, the best known and universally accepted theory on genetics and inheritance. The

4、 theory deals with known factors and with a single trait and the manner in which these qualities are transmitted.What other theories of inheritance and genetics do you know?2022/9/1562. Gregor Mendel and the Birth of Genetics格里戈-孟德爾和遺傳學(xué)的誕生2022/9/157Gregor Mendel, an Augustinian :gstinin monk mk in t

5、he monastery mnstri at Brunn, Austria, is known as the “father of genetics”.格里戈 -孟德爾，是奧地利布魯恩的修道院的一名奧古斯丁修道士,是眾所周知的遺傳學(xué)之父。2022/9/158Having 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 carefu

6、lly planned experiments that demonstrated the particulate ptikjulit nature of heredity hrediti . 孟德爾曾在讀大學(xué)時學(xué)習(xí)（接觸）了物質(zhì)的粒子屬性,并且，孟德爾有數(shù)學(xué)基礎(chǔ)，于是，他進(jìn)行了一系列周密安排的實驗來證實遺傳的顆粒屬性。2022/9/159His revolutionary ideas were neither understood nor accepted until many years after Mendel died.直到他去世后若干年，他的創(chuàng)新性的理論才被理解和接受。2022/9/

7、15103. Mendels Classic Experiments孟德爾的經(jīng)典實驗2022/9/1511Mendel 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). 孟德爾通過豌豆育種實驗來研究遺傳學(xué)，豌豆是自花授粉的,并且是真實遺傳的(每個子代和親

8、本的遺傳特征是一樣的)。2022/9/1512To test the blending theory, he focused his research on seven distinct characters.為驗證混合理論，他的研究主要集中在7個不同的特征上。2022/9/1513Each of these characters, such as seed color and plant height, present only two, clear-cut possibilities.每個特征如種子顏色，植株高度等，都只有兩個明確的可能性。He also recorded the type

9、 and number of all progeny produced from each pair of parent pea plants, and followed the results of each cross for two generations.他也記錄了來自于每一對親本的所有子代的類型和數(shù)量，和兩個子代雜交的結(jié)果。2022/9/1514 For each of the characters he studied, Mendel found that one trait was dominant dminnt while the other was recessive ris

10、esiv .對于他研究的每個特征而言，孟德爾發(fā)現(xiàn)一個特征是顯性的,那么另一個就是隱性的。 In the second filial filjl (F2) generation, the ratio of dominant to recessive was 3:1. 在子2代中, 顯性與隱性比為31。 2022/9/1515Mendel deduced that this results was possible only if each individual possesses only two hereditary units, one from each parent. 孟德爾推論:只有在

11、每個個體僅擁有兩個遺傳單元，并每個單元來自一個親本時，實驗結(jié)果才成立。2022/9/1516The units Mendel hypothesized haipisaiz are today known as alleles li:l , alternative forms of genes. 孟德爾假設(shè)的遺傳單元就是今天共識的等位基因,基因的兩種形式。 Genes are the basic units of heredity. 基因是遺傳的基本單元.2022/9/1517An organism that inherits identical alleles for a trait from

12、 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. 從親本遺傳而來的是一個特征的兩個相同的等位基因的個體被認(rèn)為是純合的。反之,遺傳而來的是兩個不同的等位基因的個體，就是雜合的。2022/9/1518 When an organism is heterozygous for a trait, the resulting

13、phenotype for that trait expresses only the dominant allele.對某一個特征而言,當(dāng)個體是雜合時，它的表型僅由顯性基因決定。Thus, the organisms phenotype fi:ntaip its physical appearance and propertiesdiffers from its genotype dentaip , which may include both a dominant and a recessive allele. 因此，生物的表型與基因型是不同的,表型是個體的物理特征和品質(zhì), 而基因型包括一

14、個顯性基因和一個隱性基因。 2022/9/1519 A pictorial representation of all possible combination of a genetic cross is known as a Punnett square.遺傳雜交的所有可能的組合圖表被稱為旁納特方格。Punnett square：a method used to determine the probabilities of combination in a zygote zaigut .2022/9/1520The results of Mendels experiments on domi

15、nant and recessive inheritance led to Mendels first law: the law of segregation.基于顯性和隱性遺傳的實驗結(jié)果,孟德爾提出了分離定律。2022/9/1521This law states that for a given trait an organism inherits one allele from each parent. 該定律認(rèn)為:對一個給定的特征而言,個體從每個親本獲得一個等位基因。 Together these alleles form the allele pair.這些等位基因一起形成等位基因?qū)Α?/p>

16、2022/9/1522 When gametes gmi:t are formed during meiosis, the two alleles become separated (halving of chromosome number). 減數(shù)分裂期形成配子時兩個等位基因分離(染色體數(shù)目的減半)。2022/9/1523Test cross：a cross between a heterozygote of unknown genotype and an individual homozygous for the recessive genes in question.To gain ev

17、idence 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. 為驗證此理論，他做了測交實驗，即基因型未知的植物個體與純合隱性的個體雜交。2022/9/1524The ratio of dominant phenotypes (if any) in the progeny makes clear whether the

18、 unknown genotype is heterozygous hetruzaigs , homozygous dominant, or homozygous recessive.子代顯性表型的比例可以明確測得該未知基因型是雜合的, 純合顯性的,還是純合隱性的。 2022/9/15254. Mendels ideas and the law of independent assortment2022/9/1526 Mendel also performed dihybrid daihaibrid crosses, which enabled him to consider how two

19、traits are inherited relative to one another. 孟德爾也進(jìn)行了雙因子雜交試驗，該實驗說明了兩個特征相互間是如何遺傳的。 2022/9/1527This work led to the law of independent assortment, which states that the alleles of genes governing different characters are inherited independently. 試驗結(jié)果產(chǎn)生了自由組合定律，即控制不同性狀的等位基因是獨立遺傳的。2022/9/1528An apparent

20、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.孟德爾定律的一個特例是，不完全顯性，即雜交后子代的表型是父母親本的中間類型。 2022/9/1529However, incomplete dominance reflects the fact that both alleles for the trait in ques

21、tion exert an effect on the phenotype. 但是，不完全顯性說明了兩個等位基因可能對表型有影響。The alleles themselves remain separate.等位基因本身仍然是分離的。2022/9/1530 Mendel presented his ideas in 1866 in a scientific paper published by the Brunn Society for Natural History. 1866年，孟德爾將其想法發(fā)表在由布魯恩自然歷史學(xué)會出版的科學(xué)論文上。 Unfortunately, the meaning

22、 of his research was not understood by other scientists of the day. 不幸運(yùn)的是，他的研究沒被當(dāng)時科學(xué)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（科倫斯和德弗里斯）發(fā)現(xiàn)。 2022/9/15315. Chromosomes and Mendelian Genetics2022/9/1532Soon after Mendels work wa

23、s rediscovered, Walter Sutton and Theodor Boveri independently proposed that the hereditary units might be located on chromosomes. 孟德爾著作再次被發(fā)現(xiàn)不久，Walter Sutton 和Theodor Boveri（薩頓和鮑維里）提出，遺傳單位可能定位在染色體上。 Experiments to prove this hypothesis were carried out by Thomas Hunt Morgan and his students at Colum

24、bia University, in research on the sex chromosomes of fruit flies.哥倫比亞大學(xué)的Thomas Hunt Morgan（摩爾根） 和他的學(xué)生進(jìn)行的果蠅伴性遺傳的研究證明了這一觀點。2022/9/1533Morgons studies were also the first exploration of sex-linked traits. 同時，Morgan也是研究伴性性狀的第一位科學(xué)家。 It also led to the discovery in 1916 by Calvin Bridges of the phenomeno

25、n of nondisjunction nndisdnkn , in which a chromosome pair fails to segregate during meiosis.1916年，伴性遺傳也導(dǎo)致了Calvin Bridges（C.布里奇斯）的不分離現(xiàn)象的發(fā)現(xiàn)，即在減數(shù)分裂中，染色體對不分離。2022/9/1534The end!pangenesis pndenisis泛生說gametes mtzcharacteristics krktristikprogeny prdinidominant dminntrecessive risesiv .filial filjlexert英

26、gz:talleles li:lhomozygous hmzaigsheterozygous hetruzaigsphenotype fi:ntaipgenotype dentaipgametes gmi:tdihybrid daihaibrid2022/9/1537Chemical Abstract Service2022/9/1538化學(xué)文摘服務(wù)社CAS（Chemical Abstract Service）美國化學(xué)學(xué)會（ACS）旗下所出版的Chemical Abstract化學(xué)文摘的在線版數(shù)據(jù)庫.“化學(xué)文摘”是化學(xué)和生命科學(xué)研究領(lǐng)域中不可或缺的參考和研究工具，也是資料量最大，最具權(quán)威的出版物。 About CAS2022/9/15392022/9/1540The CAS Source Index (CASSI) Search Tool is another free online resource intended to support researchers and librarians who need accurate bibliographic information. Use this free tool to quickly identify or confirm journal titles and abbreviatio