生物专业英语 第十一章

1、Lesson Four Genetics (from Ancient Greek , genitive and that from , origin), a discipline of biology, is the science of genes, heredity, and variation in living organisms. Genetics deals with the molecular structure and function of genes, gene behavior in context of a cell or organism (e.g. dominanc

2、e and epigenetics), patterns of inheritance from parent to offspring, and gene distribution, variation and change in populations, such as through Genome-Wide Association Studies. Given that genes are universal to living organisms, genetics can be applied to the study of all living systems, from viru

3、ses and bacteria, through plants and domestic animals, to humans (as in medical genetics). In genetic epidemiology, a genome-wide association study (GWA study, or GWAS), also known as whole genome association study (WGA study, or WGAS), is an examination of many common genetic variants in different

4、individuals to see if any variant is associated with a trait. GWAS typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major diseases. These studies normally compare the DNA of two groups of participants: people with the disease (cases) and similar people w

5、ithout (controls). Each person gives a sample of DNA, from which millions of genetic variants are read using SNP arrays. If one type of the variant (one allele) is more frequent in people with the disease, the SNP is said to be associated with the disease. The associated SNPs are then considered to

6、mark a region of the human genome which influences the risk of disease. The study of the processes involved in the unfolding development of an organism. This includes phenomena such as X chromosome inactivation in mammalian females, and gene silencing within an organism. The study of heritable chang

7、es in gene function that occur without a change in the sequence of nuclear DNA. This includes the study of how environmental factors affecting a parent can result in changes in the way genes are expressed in the offspring. In biology, and specifically genetics, epigenetics is the study of heritable

8、changes in gene expression or cellular phenotype caused by mechanisms other than changes in the underlying DNA sequence hence the name -genetics. It refers to functionally relevant modifications to the genome that do not involve a change in the nucleotide sequence. Examples of such changes are DNA m

9、ethylation and histone modification, both of which serve to regulate gene expression without altering the underlying DNA sequence. These changes may remain through cell divisions for the remainder of the cells life and may also last for multiple generations. However, there is no change in the underl

10、ying DNA sequence of the organism; instead, non-genetic factors cause the organisms genes to behave differently. There are however objections to the use of term epigenetic to describe chemical modification of histone since there is little evidence that these modifications are heritable. Specific epi

11、genetic processes include paramutation, bookmarking, imprinting, gene silencing, X chromosome inactivation, position effect, reprogramming, transvection, maternal effects, the progress of carcinogenesis, many effects of teratogens, regulation of histone modifications and heterochromatin, and technic

12、al limitations affecting parthenogenesis and cloning. In genetics and epigenetics, bookmarking is a biological phenomenon believed to function as an epigenetic mechanism for transmitting cellular memory of the pattern of gene expression in a cell, throughout mitosis, to its daughter cells. This is v

13、ital for maintaining the phenotype in a lineage of cells so that, for example, liver cells divide into liver cells and not some other cell type. Transvection is an epigenetic phenomenon that results from an interaction between an allele on one chromosome and the corresponding allele on the homologou

14、s chromosome. Transvection can lead to either gene activation or repression. Formally, it can also occur between nonallelic regions of the genome as well as regions of the genome that are not transcribed. Epigenetic research uses a wide range of molecular biologic techniques to further our understan

15、ding of epigenetic phenomena, including chromatin immunoprecipitation (together with its large-scale variants ChIP-on-chip and ChIP-Seq), fluorescent in situ hybridization, methylation-sensitive restriction enzymes, DNA adenine methyltransferase identification (DamID) and bisulfite sequencing. Furth

16、ermore, the use of bioinformatic methods is playing an increasing role (computational epigenetics). Allele li:l n 等位基因等位基因; 基因等位基因等位 dihybrid cross 双因子杂种杂交；双因子杂双因子杂种杂交；双因子杂合子杂交合子杂交 Dominant dminnt a. 占优势的；占优势的；n. 显性显性 Gene di:n n. 基因基因 Genotype dentaip n. 基因型基因型 germ plasm theory 种质说种质说 An allele is

17、 one of two or more forms of a gene or a genetic locus (generally a group of genes). The form allel is also used, an abbreviation of allelomorph. Sometimes, different alleles can result in different observable phenotypic traits, such as different pigmentation. However, many variations at the genetic

18、 level result in little or no observable variation. Most multicellular organisms have two sets of chromosomes, that is, they are diploid. These chromosomes are referred to as homologous chromosomes. Diploid organisms have one copy of each gene (and therefore one allele) on each chromosome. If both a

19、lleles are the same, they are homozygotes. If the alleles are different, they are heterozygotes. The term germ plasm was first used by the German biologist August Weismann (18341914). His germ plasm theory states that multicellular organisms consist of germ cells that contain and transmit heritable

20、information, and somatic cells which carry out ordinary bodily functions. Germ plasm theory In the germ plasm theory, inheritance in a multicellular organism only takes place by means of the germ cells: the gametes, such as egg cells and sperm cells. Other cells of the body do not function as agents

21、 of heredity. The effect is one-way: germ cells produce somatic cells, and more germ cells; the germ cells are not affected by anything the somatic cells learn or any ability the body acquires during its life. Genetic information cannot pass from soma to germ plasm and on to the next generation. The

22、 genotype is the genetic makeup of a cell, an organism, or an individual (i.e. the specific allele makeup of the individual) usually with reference to a specific character under consideration. Ones genotype differs subtly from ones genomic sequence. A sequence is an absolute measure of base composit

23、ion of an individual, or a representative of a species or group; a genotype typically implies a measurement of how an individual differs or is specialized within a group of individuals or a species. So typically, one refers to an individuals genotype with regard to a particular gene of interest and,

24、 in polyploid individuals, it refers to what combination of alleles the individual carries. The genetic constitution of an organism is referred to as its genotype, such as the letters Bb. (B - dominant genotype and b - recessive genotype).2022-7-7242022-7-7252022-7-7282022-7-730dihybrid crossdihybri

25、d crossIn contrast to a monohybrid cross, a dihybrid cross is a cross between F1 offspring (first-generation offspring) of two individuals that differ in two traits of particular interest. Heterozygous ,hetruzaigs a. 生生杂合杂合的的 Homozygous ,hmzaigus a. 生生同型结同型结合的合的, 纯合子的纯合子的 incomplete dominance 不完全显性不

26、完全显性 law of independent assortment 孟德尔第三孟德尔第三定律；自由组合律；独立分配律；自由组定律；自由组合律；独立分配律；自由组合定律合定律 law of segregation 分异定律；分离律；分分异定律；分离律；分离定律；孟德尔第二定律离定律；孟德尔第二定律 Incomplete dominance occurs when the phenotype of the heterozygous genotype is distinct from and often intermediate to the phenotypes of the homozygou

27、s genotypes. For example, the snapdragon flower color is either homozygous for red or white. When the red homozygous flower is paired with the white homozygous flower, the result yields a pink snapdragon flower. The pink snapdragon is the result of incomplete dominance. Codominance refers to a relat

28、ionship between two alleles of a gene. It occurs when the contributors of both alleles (genes) are clearly visible and do not overpower each other in the phenotype. This also means that the genotype is heterozygous. For instance, in the ABO system, the IA and IB alleles are co-dominant in producing

29、the AB blood group phenotype, in which both A- and B-type antigens are made. 2022-7-7552022-7-756 Nondisjunction nndisdkn n. 不分不分离离 Pangenesis pndenisis n. ( 英国博物学英国博物学家达尔文晚年提出的用来说明获得性状能家达尔文晚年提出的用来说明获得性状能遗传的遗传的) 泛生论；泛生说泛生论；泛生说 Phenotype fi:ntaip n. 显型；表现型显型；表现型 Punnett square 庞纳特方格庞纳特方格 Recessive ri

30、sesiv a. 退行的退行的, 逆行的逆行的, 劣性劣性的，隐性的的，隐性的 test cross 测交测交2022-7-762 Inherit inherit v. 继承继承 Inheritance inheritns n. 遗传遗传, 遗产遗产 Hereditary hireditri a. 世袭的世袭的, 遗传的遗传的 Incorporate ink:preit a. 合并的合并的, 公司公司组织的组织的, 具体化的；具体化的；v. 合并合并, 组成公司组成公司, 具体具体表现表现 Distinct distikt a. (from)独特的独特的, 不同的不同的,明显的明显的, 清楚的

31、清楚的 Blend blend v. 混合；混合；n. 混合物混合物 Monk mk n. 僧侣僧侣, 修道士修道士 Monastery mnstri n. 修道院修道院, 僧侣僧侣 Demonstrate demnstreit v. 示范示范, 演示演示,证证明明, 示威示威 Particulate ptikjulit, -leit n. 微粒子微粒子 Hypothesize haipisaiz v. 假设假设, 假定假定, 猜猜测测 Alternative :lt:ntiv a. 两者择一的；两者择一的；n. 替换物替换物, 取舍；取舍；v. 两者取一两者取一 Property prpti

32、 n. 财产财产, 性质性质 Both of these early views incorporated the blending theory: they held that heritable traits of the two parents blend, so that the distinct characteristics of each are lost in offspring. Mendel carried out a series of carefully planned experiments that demonstrated the particulate natu

33、re of heredity. His revolutionary ideas were neither understood nor accepted until many years after Mendel died. To test the blending theory, he focused his research on seven distinct characters. The units Mendel hypothesized are today known as alleles, alternative forms of genes. Mendel also performed dihybrid crosses, which enabled him to consider how two traits are inherited relative to one another. This work led to the law of ind