chapter concepts
章节概念

Introduction to Genetics
遗传学导论

■ Genetics in the twenty-first century is built on a rich tradition of discovery and experimentation stretching from the ancient world through the nineteenth century to the present day.
■ 21 世纪的遗传学建立在从古代世界到 19 世纪再到现在的丰富发现和实验传统之上。

■ Transmission genetics is the general process by which traits controlled by genes are transmitted through gametes from generation to generation.
■ 传递遗传学是基因控制的性状通过配子代代传递的一般过程。

■ Mutant strains can be used in genetic crosses to map the location and distance between genes on chromosomes.
■ 突变菌株可用于遗传杂交，以绘制染色体上基因之间的位置和距离。

■ The Watson–Crick model of DNA structure explains how genetic information is stored and expressed. This discovery is the foundation of molecular genetics.
■ DNA 结构的 Watson-Crick 模型解释了遗传信息是如何存储和表达的。这一发现是分子遗传学的基础。

■ Recombinant DNA technology revolutionized genetics, was the
■ 重组 DNA 技术彻底改变了遗传学，是

foundation for the Human Genome Project, and has generated new fields that combine genetics with information technology.
人类基因组计划的基础，并产生了将遗传学与信息技术相结合的新领域。

■ Biotechnology provides genetically modified organisms and their products that are used across a wide range of fields including agriculture, medicine, and industry.
■ 生物技术提供转基因生物及其产品，用于农业、医学和工业等广泛领域。

■ Model organisms used in genetics research are now utilized in combination with recombinant DNA technology and genomics to study human diseases.
■ 用于遗传学研究的模式生物现在与重组 DNA 技术和基因组学相结合，用于研究人类疾病。

■ Genetic technology is developing faster than the policies, laws, and conventions that govern its use.
■ 基因技术的发展速度超过了管理其使用的政策、法律和惯例。

Mendelian Genetics
孟德尔遗传学

■ Inheritance is governed by information stored in discrete unit factors called genes.
■ 遗传由存储在称为基因的离散单位因子中的信息控制。

■ Genes are transmitted from generation to generation on vehicles called chromosomes.
■ 基因在称为染色体的载体上代代相传。

■ Chromosomes, which exist in pairs in diploid organisms, provide the basis of biparental inheritance.
■ 染色体在二倍体生物中成对存在，为双亲遗传提供了基础。

■ During gamete formation, chromosomes are distributed according to postulates first described by Gregor Mendel, based on his nineteenth-century research with the garden pea.
■ 在配子形成过程中，染色体根据格雷戈尔·孟德尔 （Gregor Mendel） 根据他 19 世纪对花园豌豆的研究首次描述的假设进行分布。

■ Mendelian postulates prescribe that homologous chromosomes segregate from one another and assort independently with other segregating homologs during gamete formation.
■ 孟德尔假设规定，在配子形成过程中，同源染色体彼此分离并与其他分离同源物独立分类。

■ Genetic ratios, expressed as probabilities, are subject to chance deviation and may be evaluated statistically.
■ 以概率表示的遗传比率受机会偏差的影响，可以通过统计方式进行评估。

■ The analysis of pedigrees allows predictions concerning the genetic nature of human traits.
■ 对系谱的分析可以预测人类特征的遗传性质。

Mitosis and Meiosis
有丝分裂和减数分裂

■ Genetic continuity between generations of cells and between generations of sexually reproducing organisms is maintained through the processes of mitosis and meiosis, respectively.
■ 细胞世代之间和有性繁殖生物体世代之间的遗传连续性分别通过有丝分裂和减数分裂过程来维持。

■ Diploid eukaryotic cells contain their genetic information in pairs of homologous chromosomes, with one member of each pair being derived from the maternal parent and one from the paternal parent.
■ 二倍体真核细胞以成对的同源染色体形式包含其遗传信息，每对染色体中的一个成员来自母系父母，另一个来自父系父母。

■ Mitosis provides a mechanism by which chromosomes, having been duplicated, are distributed into progeny cells during cell reproduction.
■ 有丝分裂提供了一种机制，通过这种机制，在细胞繁殖过程中，复制的染色体分布在后代细胞中。

■ Mitosis converts a diploid cell into two diploid daughter cells.
■ 有丝分裂将一个二倍体细胞转化为两个二倍体子细胞。

■ Meiosis provides a mechanism by which one member of each homologous pair of chromosomes is distributed into each gamete or spore, thus reducing the diploid chromosome number to the haploid chromosome number.
■ 减数分裂提供了一种机制，通过这种机制，每对同源染色体的一个成员分布在每个配子或孢子中，从而将二倍体染色体数减少到单倍体染色体数。

■ Meiosis generates genetic variability by distributing various combinations of maternal and paternal members into gametes or spores.
■ 减数分裂通过将母系和父系成员的各种组合分布到配子或孢子中来产生遗传变异。

■ During the stages of mitosis and meiosis, the genetic material is condensed into discrete structures called chromosomes.
■ 在有丝分裂和减数分裂阶段，遗传物质浓缩成称为染色体的离散结构。

Modification of Mendelian Ratios
孟德尔比率的修改

■ While alleles are transmitted from parent to offspring according to Mendelian principles, they sometimes fail to display the clear-cut dominant/recessive relationship observed by Mendel.
■ 虽然等位基因根据孟德尔原理从父母传给后代，但它们有时无法表现出孟德尔观察到的明确的显性/隐性关系。

■ In many cases, in contrast to Mendelian genetics, two or more genes are known to influence the phenotype of a single characteristic.
■ 在许多情况下，与孟德尔遗传学相反，已知两个或多个基因会影响单个特征的表型。

■ Still another exception to Mendelian inheritance is the presence of genes on sex chromosomes, whereby one of the sexes contains only a single member of that chromosome.
■ 孟德尔遗传的另一个例外是性染色体上存在基因，其中一种性别仅包含该染色体的一个成员。

■ Phenotypes are often the combined result of both genetics and the environment within which genes are expressed.
■ 表型通常是遗传学和基因表达环境的综合结果。

■ The result of the various exceptions to Mendelian principles is the occurrence of phenotypic ratios that differ from those resulting from standard monohybrid, dihybrid, and trihybrid crosses.
■ 孟德尔原理的各种例外的结果是出现了与标准单杂交、双杂交和三杂交杂交产生的表型比不同的表型比。

■ Extranuclear inheritance, resulting from the expression of genes present in the DNA found in mitochondria and chloroplasts, modifies Mendelian inheritance patterns. Such genes are most often transmitted through the female gamete.
■ 核外遗传是由线粒体和叶绿体中发现的 DNA 中存在的基因表达引起的，改变了孟德尔遗传模式。这种基因最常通过雌配子传递。

Sex Determination and Sex Chromosomes
性别决定和性染色体

■ A variety of mechanisms have evolved that result in sexual differentiation, leading to sexual dimorphism and greatly enhancing the production of genetic variation within species.
■ 已经进化出多种机制，导致性分化，导致性二态性，并大大增强物种内遗传变异的产生。

■ Often, specific genes, usually on a single chromosome, cause maleness or femaleness during development.
■ 通常，特定基因（通常在单条染色体上）在发育过程中会导致男性或女性。

■ In humans, the presence of extra X or Y chromosomes beyond the diploid number may be tolerated but often leads to syndromes demonstrating distinctive phenotypes.
■ 在人类中，除了二倍体数之外的额外 X 或 Y 染色体的存在可能是可以容忍的，但通常会导致表现出独特表型的综合征。

■ While segregation of sex-determining chromosomes should theoretically lead to a one-to-one sex ratio of males to females, in humans the actual ratio favors males at conception.
■ 虽然性别决定染色体的分离理论上应该导致男性与女性的性别比例为 1：1，但在人类中，实际比例在受孕时有利于男性。

■ In mammals, females inherit two X chromosomes compared to one in males, but the extra genetic information in females is compensated for by random inactivation of one of the X chromosomes early in development.
■ 在哺乳动物中，雌性继承两条 X 染色体，而雄性则继承一条，但雌性的额外遗传信息通过在发育早期随机灭活其中一条 X 染色体来补偿。

■ In some reptilian species, temperature during incubation of eggs determines the sex of offspring.
■ 在一些爬行动物物种中，卵孵化过程中的温度决定了后代的性别。

Linkage and Chromosome Mapping in Eukaryotes
真核生物的连锁和染色体定位

■ Chromosomes in eukaryotes contain many genes whose locations are fixed along the length of the chromosomes.
■ 真核生物中的染色体包含许多基因，其位置沿染色体长度固定。

■ Unless separated by crossing over, alleles present on a chromosome
■ 除非通过交叉分离，否则等位基因存在于染色体上

segregate as a unit during gamete formation.
在配子形成过程中作为一个单元分离。

■ Crossing over between homologs is a process of genetic recombination during meiosis that creates gametes with new combinations of alleles that enhance genetic variation within species.
■ 同源物之间的交叉是减数分裂过程中的遗传重组过程，它产生具有新等位基因组合的配子，从而增强物种内的遗传变异。

■ Crossing over between homologs serves as the basis for the construction of chromosome maps.
■ 同源物之间的交叉是构建染色体图谱的基础。

■ While exchange occurs between sister chromatids during mitosis, no new recombinant chromatids are created.
■ 虽然在有丝分裂过程中姐妹染色单体之间发生交换，但不会产生新的重组染色单体。

Quantitative Genetics and Multifactorial Traits
定量遗传学和多因素性状

■ Quantitative inheritance results in a range of measurable phenotypes for a polygenic trait.
■ 数量遗传导致多基因性状的一系列可测量表型。

■ Polygenic traits most often demonstrate continuous variation.
■ 多基因性状最常表现出连续变异。

■ Quantitative inheritance can be explained in Mendelian terms whereby certain alleles have an additive effect on the traits under study.
■ 数量遗传可以用孟德尔术语来解释，其中某些等位基因对所研究的性状具有加性影响。

■ The study of polygenic traits relies on statistical analysis.
■ 多基因性状的研究依赖于统计分析。

■ Heritability values estimate the genetic contribution to phenotypic
■ 遗传力值估计遗传对表型的贡献

variability under specific environmental conditions.
特定环境条件下的可变性。

■ Twin studies allow an estimation of heritability in humans.
■ 双胞胎研究允许估计人类的遗传力。

■ Quantitative trait loci (QTLs) can be mapped and identified.
■ 数量性状位点 （QTL） 可以进行定位和鉴定。

Chromosome Mutations: Variation in Number and Arrangement
染色体突变：数量和排列的变化

■ The failure of chromosomes to properly separate during meiosis results in variation in the chromosome content of gametes and subsequently in offspring arising from such gametes.
■ 染色体在减数分裂过程中未能正确分离，导致配子染色体内容的变化，随后由此类配子产生的后代发生变化。

■ Plants often tolerate an abnormal genetic content, but, as a result, they often manifest unique phenotypes. Such genetic variation has been an important factor in the evolution of plants.
■ 植物通常耐受异常的遗传内容，但因此，它们经常表现出独特的表型。这种遗传变异一直是植物进化的一个重要因素。

■ In animals, genetic information is in a delicate equilibrium whereby the gain or loss of a chromosome, or part of a chromosome, in an otherwise diploid organism often leads to lethality or to an abnormal phenotype.
■ 在动物中，遗传信息处于微妙的平衡状态，因此在其他二倍体生物体中，染色体或染色体部分的获得或丢失通常会导致致死或异常表型。

■ The rearrangement of genetic information within the genome of a diploid organism may be tolerated by that organism but may affect the viability of gametes and the phenotypes of organisms arising from those gametes.
■ 二倍体生物体基因组内遗传信息的重排可能被该生物体所容忍，但可能会影响配子的活力和由这些配子产生的生物体的表型。

■ Chromosomes in humans contain fragile sites—regions susceptible to breakage, which lead to abnormal phenotypes.
■ 人类的染色体包含脆弱的位点——易断裂的区域，从而导致异常的表型。

Gene Mutation, DNA Repair, and Transposition
基因突变、DNA 修复和转座

■ Mutations comprise any change in the nucleotide sequence of an organism’s genome.
■ 突变包括生物体基因组核苷酸序列的任何变化。

■ Mutations are a source of genetic variation and provide the raw material for natural selection. They are also the source of genetic damage that contributes to cell death, genetic diseases, and cancer.
■ 突变是遗传变异的来源 ， 为自然选择提供原材料。它们也是导致细胞死亡、遗传疾病和癌症的遗传损伤的来源。

■ Mutations have a wide range of effects on organisms depending on the type of base-pair alteration, the location of the mutation within the chromosome, and the function of the affected gene product.
■ 突变对生物体的影响范围很广，具体取决于碱基对改变的类型、突变在染色体内的位置以及受影响基因产物的功能。

■ Mutations can occur spontaneously as a result of natural biological and chemical processes, or they can be induced by external factors, such as chemicals or radiation.
■ 突变可能是自然生物和化学过程自发发生的，也可能是由外部因素（如化学或辐射）诱导的。

■ Single-gene mutations cause a wide variety of human diseases.
■ 单基因突变会导致多种人类疾病。

■ Organisms rely on a number of DNA repair mechanisms to counteract mutations. These mechanisms range from proofreading and correction of replication errors to base excision and homologous recombination repair.
■ 生物体依靠许多 DNA 修复机制来抵消突变。这些机制包括从复制错误的校对和校正到碱基切除和同源重组修复。

■ Mutations in genes whose products control DNA repair lead to genome hypermutability, human DNA repair diseases, and cancers.
■ 其产物控制 DNA 修复的基因突变会导致基因组超突变、人类 DNA 修复疾病和癌症。

■ Transposable elements may move into and out of chromosomes, causing chromosome breaks and inducing mutations both within coding regions and in gene-regulatory regions.
■ 转座因子可能移入和移出染色体，导致染色体断裂并在编码区和基因调控区内诱导突变。

Population and Evolutionary Genetics
种群和进化遗传学

■ Most populations and species harbor considerable genetic variation.
■ 大多数种群和物种都具有相当大的遗传变异。

■ This variation is reflected in the alleles distributed among populations of a species.
■ 这种变异反映在一个物种种群之间的等位基因分布中。

■ The relationship between allele frequencies and genotype frequencies in an ideal population is described by the Hardy–Weinberg law.
■ 理想群体中等位基因频率和基因型频率之间的关系由 Hardy-Weinberg 定律描述。

■ Selection, migration, and genetic drift can cause changes in allele frequency.
■ 选择、迁移和遗传漂变会导致等位基因频率的变化。

■ Mutation creates new alleles in a population gene pool.
■ 突变在群体基因库中产生新的等位基因。

■ Nonrandom mating changes population genotype frequency but not allele frequency.
■ 非随机交配改变种群基因型频率，但不改变等位基因频率。

■ A reduction in gene flow between populations, accompanied by selection or genetic drift, can lead to reproductive isolation and speciation.
■ 种群之间基因流动的减少，伴随着选择或遗传漂变，可导致生殖隔离和物种形成。

■ Genetic differences between populations or species are used to reconstruct evolutionary history.
■ 种群或物种之间的遗传差异用于重建进化历史。