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  • 案例研究结论:家庭癌症

    lesson content

    Pedigree for Rebecca's family, as described in the beginning of this chapter, showing individuals with cancer (red) and those that do not have cancer (blue). Circles represent women, squares represent men.
    ::如本章开头所述,Rebecca家庭Pedigree显示有癌症(红)和没有癌症(蓝)的个人,圆圈代表妇女,平方代表男子。

    Case Study Conclusion: Cancer in the Family
    ::案例研究结论:家庭癌症

    Rebecca’s family tree, as illustrated in the pedigree above, shows a high incidence of cancer among close relatives. But are genes the cause of cancer in this family? Only genetic testing, which is the sequencing of specific genes in an individual, can reveal whether a cancer-causing gene is being inherited in this family.
    ::Rebecca的家族树(如上文小说所示)表明近亲中癌症的发病率很高。 但基因是这个家族癌症的原因吗? 只有基因测试 — — 这是个人特定基因的顺序 — — 才能揭示这个家族是否继承了致癌基因。

    Fortunately for Rebecca, the results of her genetic testing show that she does not have the mutations in the BRCA1 and BRCA2 genes that most commonly increase a person’s risk of getting cancer. This doesn't mean, however,  that she doesn’t have other mutations in these genes that could increase her risk of getting cancer. There are many other mutations in BRCA genes whose effect on cancer risk is still not known — and there may be many more yet to be discovered. The picture from the National Cancer Institute illustrates many of the different types of known mutations in the BRCA1 gene. It is important to continue to study the variations in genes such as BRCA in different people to better assess their possible contribution to the development of disease. As you now know from this chapter, many mutations are harmless, while others can cause significant health effects, depending on the specific mutation and the gene involved.
    ::幸运的是,对Rebecca来说,她的基因测试结果显示,她没有BRCA1和BRCA2基因的突变,这些突变通常会增加一个人患癌症的风险。 但这并不意味着她在这些基因中没有其他突变,这可能会增加她患癌症的风险。 在BRCA基因中还有许多其他突变,这些突变对癌症风险的影响还不得而知 — — 可能还有更多的变异有待发现。 国家癌症研究所的图片显示了BRCA1基因中已知的多种不同的突变类型。 继续研究不同人群的BRCA等基因的变异非常重要,以更好地评估其对疾病发展可能做出的贡献。 正如你现在从这一章中知道的那样,许多突变是无害的,而其他突变可能造成重大的健康影响,取决于具体的突变和涉及的基因。

    lesson content

    Mutations in the BRCA1 gene. Use the knowledge you gained from this chapter to define nonsense, frameshift, and missense mutations. Do these tend to be neutral or harmful mutations?
    ::BRCA1 基因变异。 使用您从本章获得的知识来定义无稽、 框架变换和 missense 突变。 这些变异倾向于中性还是有害的变异?

    Mutations in BRCA genes are particularly likely to cause cancer because these genes encode for tumor-suppressor proteins that normally repair damaged DNA and control cell division. If these genes are mutated in a way that causes the proteins to not function properly, other mutations can accumulate and cell division can run out of control, which can cause cancer.
    ::BRCA基因中的突变特别可能引发癌症,因为这些基因为通常修复受损的DNA和控制细胞分解的肿瘤抑制蛋白编码。 如果这些基因变异导致蛋白质不能正常运转,其他突变会累积,细胞分解会失去控制,导致癌症。

    BRCA1 and BRCA2 are on chromosomes 17 and 13, respectively, which are autosomes. As Rebecca’s genetic counselor mentioned, mutations in these genes have a dominant inheritance pattern. Now that you know the pattern of inheritance of autosomal dominant genes, if Rebecca’s grandmother did have one copy of a mutated BRCA gene, what are the chances that Rebecca’s mother also has this mutation? Because it is dominant, only one copy of the gene is needed to increase the risk of cancer, and because it is on autosomes instead of sex chromosomes, the sex of the parent or offspring does not matter in the inheritance pattern. In this situation, Rebecca’s grandmother’s eggs would have had a 50 percent chance of having a BRCA gene mutation (Mendel’s law of segregation). Therefore, Rebecca’s mother would have had a 50 percent chance of inheriting this gene. Even though Rebecca does not have the most common BRCA mutations that increase the risk of cancer, it does not mean that her mother does not, because there would also only be a 50 percent chance that she would pass it on to Rebecca. Rebecca’s mother, therefore, should consider getting tested for mutations in the BRCA genes, as well. Ideally, the individuals with cancer in a family should be tested first when a genetic cause is suspected, so that if there is a specific mutation being inherited, it can be identified, and the other family members can be tested for that same mutation.
    ::BRCA1 和 BRCA2 分别出现在17和13个染色体上,这两个染色体是异体。 正如Rebecca的遗传顾问所说,这些基因的突变具有占支配地位的继承模式。 现在,你知道了自动合成主要基因的遗传模式,如果Rebecca的祖母确实拥有一个变异的BRCA基因的复制件,Rebecca的母亲也有这种变异的可能性有多大?由于它具有主导性,因此只需要一份基因的复制件来增加癌症的风险,并且因为它是自动变异体,而不是性染色体,父母或后代的性别在继承模式中并不重要。 在这种情况下,Rebecca的祖母蛋蛋有50%的遗传基因突变机会(Mendel的隔离法 ) 。 因此,Rebecca的母亲有50%的遗传基因遗传基因遗传变异的机会。 尽管Rebecca没有增加癌症风险的最常见的BRCA突变基因,但这并不意味着她母亲不会这样做,因为只有50%的遗传基因变种才能被测试。 因此,她的母亲会认为自己在BRCA中会具有这样的基因变种。

    Mutations in both BRCA1 and BRCA2 are often found in Ashkenazi Jewish families. However, these genes are not linked in the chromosomal sense, because they are on different chromosomes and are therefore inherited independently, in accordance with Mendel’s law of independent assortment. Why would certain gene mutations be prevalent in particular ethnic groups? If people within an ethnic group tend to produce offspring with each other, their genes will remain prevalent within the group. These may be genes for harmless variations such as skin, hair, or eye color, or harmful variations such as the mutations in the BRCA genes. Other genetically based diseases and disorders are sometimes more commonly found in particular ethnic groups, such as cystic fibrosis in people of European descent, and sickle cell anemia in people of African descent. You will learn more about the prevalence of certain genes and traits in particular ethnic groups and populations in the chapter on Human Variation.
    ::BRCA1和BRCA2的突变经常出现在Ashkenazi犹太家庭中,然而,这些基因在染色体意义上没有联系,因为它们存在于不同的染色体上,因此根据Mendel的独立相色谱法,它们是独立继承的。为什么某些基因突变在特定种族群体中很普遍?如果一个族裔群体中的人倾向于相互产生后代,他们的基因在群体中仍然很普遍。这些基因可能是皮肤、头发或眼色等无害变异的基因,或BRCA基因突变等有害变异的基因。其他基于基因的疾病和失调有时在特定的族裔群体中比较常见,例如欧洲血统的人的细胞纤维化,以及非洲人后裔的镰状细胞贫血。你会在人类变异一章中更多地了解某些基因和特征的流行情况,特别是族裔群体和人口。

    As you learned in this chapter, genetics is not the sole determinant of phenotype. The environment can also influence many traits, including  adult height and skin color. The environment plays a major role in the development of cancer, too. Ninety  to 95 percent of all cancers do not have an identified genetic cause, and are often caused by mutagens in the environment, such as UV radiation from the sun or toxic chemicals in cigarette smoke. But for families like Rebecca’s, knowing their family health history and genetic makeup may help them better prevent or treat diseases that are caused by their genetic inheritance. If a person knows they have a gene that can increase their risk of cancer, they can make lifestyle changes and have early and more frequent cancer screenings. They may even choose to have preventative surgeries that can  help reduce their risk of getting cancer and increase their odds of long-term survival if cancer does occur. The next time you go to the doctor and they ask whether any members of your family have had cancer, you will have a deeper understanding why this information is so important to your health.
    ::正如您在本章中所了解到的,遗传学并非是人型的唯一决定因素。环境也可以影响许多特征,包括成年身高和肤色。环境在癌症发育中也起着重要作用。90%至95%的癌症没有确定的遗传原因,而且往往是环境中的诱变性造成的,如太阳紫外辐射或烟雾中的有毒化学物质。 但是,对于丽贝卡这样的家庭来说,了解他们的家庭健康历史和基因化妆可以帮助他们更好地预防或治疗其遗传遗传遗产造成的疾病。 如果一个人知道他们拥有可以增加癌症风险的基因,他们可以改变生活方式,并进行早期和更频繁的癌症筛查。他们甚至可以选择预防性手术,帮助降低癌症的风险,并在癌症发生时增加他们长期存活的可能性。你下次去看医生时,他们询问你的家人是否有癌症,你会更深入地了解为什么这种信息对你的健康如此重要。

    Chapter Summary
    ::章次摘要

    In this chapter you learned about genetics — the science of heredity. Specifically you learned that:
    ::在本章中,你学到了遗传学——遗传科学。

    • Chromosomes are structures made of DNA and proteins that are encoded with genetic instructions for making RNA and proteins. The instructions are organized into units called genes, which are segments of DNA that code for particular pieces of RNA. The RNA molecules can then act as a blueprint for proteins, or directly help regulate various cellular processes.
      ::染色体是由DNA和蛋白质组成的结构,并配有用于制作RNA和蛋白质的基因说明。 这些说明被组织成称为基因的单位,这些基因是DNA的一部分,可以编码RNA的具体部分。 然后RNA分子可以作为蛋白质的蓝图,或者直接帮助调节各种细胞过程。


      ::染色体是由DNA和蛋白质组成的结构,并配有用于制作RNA和蛋白质的基因说明。 这些说明被组织成称为基因的单位,这些基因是DNA的一部分,可以编码RNA的具体部分。 然后RNA分子可以作为蛋白质的蓝图,或者直接帮助调节各种细胞过程。
    • Humans normally have 23 pairs of chromosomes. Of these, 22 pairs are autosomes, which contain genes for characteristics unrelated to sex. The other pair consists of sex chromosomes (XX in females, XY in males). Only the Y chromosome contains genes that determine sex.
      ::人类通常有23对染色体,其中22对是异体,含有与性别无关特性的基因,另一对是性染色体(女性为XX,男性为XY)。只有Y染色体含有决定性别的基因。
    • Humans have an estimated 20 thousand to 22 thousand genes. The majority of human genes have two or more possible versions, called alleles.
      ::人类估计有2万至2万2千个基因,大多数人类基因有两种或两种以上可能的基因,叫做异灵。
    • Genes that are located on the same chromosome are called linked genes. Linkage explains why certain characteristics are frequently inherited together.
      ::位于同一染色体上的基因被称为关联基因。 链接解释了为什么某些特征经常被一起继承。
    • Determining that DNA is the genetic material was an important milestone in biology.
      ::确定DNA是遗传物质是生物学的一个重要里程碑。
      • In the 1920s, Griffith showed that something in virulent bacteria could be transferred to nonvirulent bacteria, making them virulent, as well.
        ::1920年代,格里菲斯表明 毒细菌中的东西 可以转移到非病毒细菌, 使它们也变得毒害。
      • In the 1940s, Avery and colleagues showed that the "something" Griffith found was DNA and not protein. This result was confirmed by Hershey and Chase, who demonstrated that viruses insert DNA into bacterial cells.
        ::20世纪40年代,艾弗里和同事证明葛里菲斯发现的“某事”是DNA,而不是蛋白质。 赫希和大通证实了这一结果,他们证明病毒将DNA插入细菌细胞。

      ::1920年代,格里菲斯(Griffith)指出,毒细菌中的某些东西可以转移到非病毒细菌,使它们也成为毒药。 在1940年代,艾弗里(Avery)和同事(同事)指出,葛里菲斯发现的“东西”是DNA,而不是蛋白质。 赫希(Hershey)和大通(Chase)证实了这一结果,他们证明病毒将DNA插入细菌细胞。
    • In the 1950s, Chargaff showed that in DNA, the concentration of adenine is always the same as the concentration of thymine, and the concentration of guanine is always the same as the concentration of cytosine. These observations came to be known as Chargaff's rules.
      ::20世纪50年代,电源显示,在DNA中,的浓度总是与甲状腺的浓度相同,而的浓度总是与乙酸的浓度相同。 这些观察结果被称为“电源规则 ” 。
    • In the 1950s, James Watson and Francis Crick, building on the prior X-ray research of Rosalind Franklin and others, discovered the double helix structure of the DNA molecule.
      ::1950年代,詹姆斯·沃森和弗朗西斯·克里克在Rosalind Franklin和其他人先前的X光研究的基础上,发现了DNA分子的双螺旋结构。
    • Knowledge of DNA's structure helped scientists understand how DNA replicates, which must occur before cell division. DNA replication is semi-conservative because each daughter molecule contains one strand from the parent molecule and one new strand that is complementary to it.
      ::对DNA结构的了解有助于科学家了解DNA复制的方式,而DNA复制必须在细胞分裂之前发生。 DNA复制是半保守性的,因为每个女分子都含有母分子的一丝和补充该分子的新一丝。
    • The central dogma of molecular biology can be summed up as: DNA → RNA → Protein. This means that the genetic instructions encoded in DNA are transcribed to RNA. From RNA, they are translated into a protein.
      ::分子生物学的核心教条可以概括为:DNA RNA Protein。 这意味着DNA编码的基因指示被转录到 RNA 。 从 RNA 中,它们被转化成蛋白质 。
    • RNA is a nucleic acid. Unlike DNA, RNA consists of just one polynucleotide chain instead of two, contains the base uracil instead of thymine, and contains the sugar ribose instead of deoxyribose.
      ::RNA是一种核酸。 与DNA不同的是,RNA只包含一个聚核酸链,而不是两个链,含有基极核素,而不是甲状腺,并含有糖核素而不是脱氧核素。
    • The main function of RNA is to help make proteins. There are three main types of RNA: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
      ::RNA的主要功能是帮助制造蛋白质,有三种主要的RNA类型:信使RNA(mRNA)、RNA(rRNA)和传输RNA(tRNA)。
    • According to the RNA world hypothesis, RNA was the first type of biochemical molecule to evolve, predating both DNA and proteins.
      ::根据RNA世界假设,RNA是第一种进化的生化分子,先是DNA和蛋白质。
    • The genetic code was cracked in the 1960s by Marshall Nirenberg. It consists of the sequence of nitrogen bases in a polynucleotide chain of DNA or RNA. The four bases make up the "letters" of the code. The letters are combined in groups of three to form code "words," or codons, each of which encodes for one amino acid or a start or stop signal.
      ::马歇尔·尼伦贝格于1960年代破解了遗传代码。 它由DNA或RNA的多核核酸链条中的氮基序列组成。 四个基点组成代码的“ 字母 ” 。 字母由三组组成, 组成代号“ 字 ” 或 codon, 每种代号都编码为一种氨酸或开始或停止信号 。
      • AUG is the start codon, and it establishes the reading frame of the code. After the start codon, the next three bases are read as the second codon, and so on until a stop codon is reached.
        ::AUG是开始的codon, 它确定了代码的阅读框架 。 在开始的codon之后, 接下来的3个基点被解读为第二个codon, 直至达到停止的codon。
      • The genetic code is universal, unambiguous, and redundant.
        ::遗传法是普遍、明确和多余的。

      ::AUG是开始的codon, 它确定了代码的阅读框架 。 在开始的codon 之后, 接下来的3个基点被解读为第二个codon, 直至达到停止的codon。 遗传代码是通用的、明确的和多余的。
    • Protein synthesis is the process in which cells make proteins. It occurs in two stages: transcription and translation.
      ::蛋白质合成是细胞制造蛋白质的过程,分两个阶段进行:转录和翻译。
      • Transcription is the transfer of genetic instructions in DNA to mRNA in the nucleus. It includes the steps of initiation, elongation, and termination. After the mRNA is processed, it carries the instructions to a ribosome in the cytoplasm.
        ::Transnation 是指将DNA中的遗传指示转移到核中的 mRNA 。 它包括启动、延展和终止步骤。 在处理 mRNA 后, 它将指示传送到细胞托盘中的血清 。
      • Translation occurs at the ribosome, which consists of rRNA and proteins. In translation, the instructions in mRNA are read, and tRNA brings the correct sequence of amino acids to the ribosome. Then rRNA helps bonds form between the amino acids, producing a polypeptide chain.
        ::由 RRNA 和 蛋白质组成 的 REBOSM 进行 翻译 。 在翻译中, 读取 mRNA 的指令, TRNA 将氨基酸的正确序列带到 REBOSM 。 然后 RRNA 帮助氨基酸 之间形成债券, 产生聚石化链 。
      • After a polypeptide chain is synthesized, it may undergo additional processing to form the finished protein.
        ::在合成了聚石化物链之后,它可能经过额外的加工,以形成成品蛋白质。

      ::Transnation 是指将DNA中的遗传指示转移到核中的 mRNA 。 它包括启动、 延展和终止步骤。 在处理 mRNA 后, 它将指示传送到细胞图拉斯姆的血清。 翻译发生在核中, 它由 RRNA 和蛋白组成。 在翻译中, 读取 mRNA 的指令, tRNA 将氨酸的正确序列带给核体。 然后 RRNA 帮助氨酸之间的粘合形式, 产生聚苯二酸链 。 在合成聚苯二酸链后, 它可能会经过额外的加工形成成蛋白质 。
    • Mutations are random changes in the sequence of bases in DNA or RNA. They are the ultimate source of all new genetic variation in any species.
      ::突变是DNA或RNA中基数序列的随机变化,是任何物种所有新的基因变异的最终来源。
      • Mutations may happen spontaneously during DNA replication or transcription. Other mutations are caused by environmental factors called mutagens.
        ::在DNA复制或转录过程中,变异可能自发发生,其他变异是由称为变异的环境因素引起的。
      • Germline mutations occur in gametes and may be passed on to offspring. Somatic mutations occur in cells other than gametes and cannot be passed on to offspring.
        ::阳性突变发生在调子中, 并可能传给后代。 体性突变发生在除调子以外的细胞中, 不能传给后代 。
      • Chromosomal alterations are mutations that change chromosome structure and usually affect the organism in multiple ways. Charcot-Marie-Tooth disease type 1  is an example of a chromosomal alteration.
        ::染色体变异是改变染色体结构的突变,通常以多种方式影响有机体。 染色体变异是染色体变异的一个例子。
      • Point mutations are changes in a single nucleotide. The effects of point mutations depend on how they change the genetic code, and may range from no effects to very serious effects.
        ::点突变是单核核酸的变化,点突变的影响取决于它们如何改变基因编码,从无影响到非常严重的影响可能不一而足。
      • Frameshift mutations change the reading frame of the genetic code and are likely to have a drastic effect on the encoded protein.
        ::框架变异改变了遗传代码的读数框架,可能对编码蛋白质产生剧烈影响。
      • Many mutations are neutral and have no effects on the organism in which they occur. Some mutations are beneficial and improve fitness, while others are harmful and decrease fitness.
        ::许多变异是中性的,对发生变异的有机体没有影响,有些变异有益,改善身体健康,而另一些变异有害,降低身体健康。

      ::在DNA复制或转录过程中,突变可能自发发生。其他突变是由环境因素(称为诱变)引发的。变异发生在调子中,并可能传给后代。体突变发生在除调子以外的细胞中,不能传给后代。染色体变异是变异,改变染色体结构,通常以多种方式影响生物体。Charcot-Marie-Tooth疾病类型1是染色体变异的一个例子。点突变是单核酸的变化。点突变的效果取决于它们如何改变遗传代码,从没有影响到非常严重的影响。框架变异会改变遗传代码的阅读框架,可能对编码蛋白产生剧烈影响。许多突变是中性的,对发生突变的有机体没有影响。一些突变有利于和增进健康,而另一些则有害和降低健康。
    • Using a gene to make a protein is called gene expression. Gene expression is regulated to ensure that the correct proteins are made when and where they are needed. Regulation may occur at any stage of protein synthesis or processing.
      ::基因表达方式受管制,以确保正确的蛋白质在需要的时候和地点产生,在蛋白质合成或加工的任何阶段都可实行管制。
      • The regulation of transcription is controlled by regulatory proteins that bind to regions of DNA called regulatory elements, which are usually located near promoters. Most regulatory proteins are either activators that promote transcription or repressors that impede transcription.
        ::转录管理由调控性蛋白控制,调控性蛋白与DNA区域结合,称为调控性元素,通常位于促销者附近,大多数调控性蛋白要么促进转录,要么阻碍转录的抑制剂。
      • A regulatory element common to almost all eukaryotic genes is the TATA box. A number of regulatory proteins must bind to the TATA box in the promoter before transcription can proceed.
        ::几乎所有电子基因的共同监管要素是TATA箱,许多监管蛋白质在转录之前必须与推广商的TATA箱捆绑,然后才能进行转录。
      • The regulation of gene expression is extremely important during the early development of an organism. Homeobox genes, which encode for chains of amino acids called homeodomains, are important genes that regulate development.
        ::基因表达的规范在生物的早期发育中极为重要。 将氨基酸链编码为家腔坏疽杆菌的Homeobox基因是调节发展的重要基因。
      • Some types of cancer occur because of mutations in genes that control the cell cycle. Cancer-causing mutations most often occur in two types of regulatory genes, called tumor-suppressor genes and proto-oncogenes.
        ::某些类型的癌症是由于控制细胞循环的基因突变而发生的,致癌突变最经常发生在两类监管基因,即肿瘤抑制基因和原致癌基因。

      ::对转录的监管由监管性蛋白控制,这些蛋白通常与DNA区域相关,称为监管性元素,通常位于促销者附近,大多数监管性蛋白要么是促进转录的活性者,要么是阻碍转录的抑制剂。几乎所有雌激素基因的一个共同监管性元素是TATA盒。一些监管性蛋白在转录之前必须与促销者中的TATA盒捆绑在一起。基因表达的监管在生物的早期发育中极为重要。为氨基酸链编码的Homeobox基因是调节发展的重要基因。某些类型的癌症是因控制细胞循环的基因突变而发生的。致癌突变通常发生在两类监管性基因中,称为肿瘤抑制基因和蛋白质。
    • Mendel experimented with the inheritance of traits in pea plants, which have two different forms of several visible characteristics. Mendel crossed pea plants with different forms of traits.
      ::Mendel实验了豆类植物特性的继承,这些植物有两种不同形式的几种可见特征,而Mendel则跨过具有不同形式的特性的豆类植物。
      • In Mendel's first set of experiments, he crossed plants that only differed in one characteristic. The results led to Mendel's first law of inheritance, called the law of segregation. This law states that there are two factors controlling a given characteristic, one of which dominates the other, and these factors separate and go to different gametes when a parent reproduces.
        ::在门德尔的第一组实验中,他跨越了只有一个不同特征的植物。结果导致了门德尔的第一个继承法,称为隔离法。 这部法律规定,有两个因素控制着一个特定特征,其中之一支配着另一个特征,而这些因素在父母生育时是分开的,转到不同的调子上。
      • In Mendel's second set of experiments, he experimented with two characteristics at a time. The results led to Mendel's second law of inheritance, called the law of independent assortment. This law states that the factors controlling different characteristics are inherited independently of each other.
        ::在Mendel的第二套实验中,他一次实验两个特征,结果导致Mendel的第二个继承法,称为独立等级法,该法规定,控制不同特征的因素是相互独立继承的。

      ::在Mendel的第一组实验中,他跨越了只有一个特点的植物。结果导致Mendel的第一部继承法,称为隔离法。该法指出,有两个因素控制着一个特定特征,其中一个主宰着另一个特征,而这些因素在父母生育时分开并转到不同的组合。在Mendel的第二组实验中,他一次试验两个特征。结果导致Mendel的第二个继承法,称为独立分类法。该法规定,控制不同特征的因素是相互独立继承的。
    • Mendel's laws of inheritance, now expressed in terms of genes, form the basis of genetics, the science of heredity. Mendel is often called the father of genetics.
      ::孟德尔的继承法现在以基因的形式表达,构成遗传学和遗传科学的基础。 孟德尔常常被称为遗传学之父。 孟德尔的继承法是遗传学之父。
    • The position of a gene on a chromosome is its locus. A given gene may have different versions called alleles. Paired chromosomes of the same type are called homologous chromosomes and they have the same genes at the same loci.
      ::染色体上的基因位置是其位置。 给定的基因可能有不同的版本, 叫做异形。 同类型的同种染色体被称为同种染色体, 在同一地点也有相同的基因。
    • The alleles an individual inherits for a given gene make up the individual's genotype. An organism with two of the same alleles is called a homozygote, and an individual with two different alleles is called a heterozygote.
      ::个体继承给定基因的等同体是个人的基因型。 两种同异异体的有机体被称为同子体,而两种异异子体则被称为异体。
    • The expression of an organism's genotype is referred to as its phenotype. A dominant allele is always expressed in the phenotype, even when just one dominant allele has been inherited. A recessive allele is expressed in the phenotype only when two recessive alleles have been inherited.
      ::有机体基因型的表达方式被称为其pheno类型。 支配型异名总是以苯型表示, 即使只继承了一个占支配地位的异名。 只有当两个隐性异名被继承时, 才会以苯型表示中性异名。
    • In sexual reproduction, two parents produce gametes that unite in the process of fertilization to form a single-celled zygote. Gametes are haploid cells with only one of each pair of homologous chromosomes, and the zygote is a diploid cell with two of each pair of chromosomes.
      ::在性生殖方面,双亲生产在受精过程中结合成单一细胞的zygote。 双胞胎是单细胞细胞,每对同族染色体中只有一对,双胞胎是每对染色体中只有两对。 双胞胎是每对染色体中只有一对。 双胞胎是每对同族染色体中只有一对。 双胞胎是每对染色体中只有两对的浸泡细胞。
    • Meiosis is the type of cell division that produces four haploid daughter cells that may become gametes. Meiosis occurs in two stages, called meiosis I and meiosis II, each of which occurs in four phases (prophase, metaphase, anaphase, and telophase).
      ::Meisisis 是一种细胞分裂型,可产生4个可能变成游戏的散发女儿细胞。 Meisis 分两个阶段发生,称为 meisisis I 和 meisis II, 每一个阶段分四个阶段( 预阶段、 元阶段、 周期阶段和 调频阶段 ) 。
    • Meiosis is followed by gametogenesis, the process in which the haploid daughter cells change into mature gametes. Males produce gametes called sperm through spermatogenesis, and females produce gametes called eggs through oogenesis.
      ::雄性动物通过精子产生基因精子,而雌性动物则通过卵子产生基因组。 雄性动物通过精子产生基因组,而雌性动物则通过卵子产生基因组。
    • Sexual reproduction produces offspring that are genetically unique. Crossing-over, independent assortment, and the random union of gametes result in a high degree of genetic variation.
      ::性生殖产生遗传上独特的后代。 交叉、独立的组合和随机的交织导致遗传变异。
    • Mendelian inheritance refers to the inheritance of traits controlled by a single gene with two alleles, one of which may be completely dominant to the other. The pattern of inheritance of Mendelian traits depends on whether the traits are controlled by genes on autosomes or by genes on sex chromosomes.
      ::孟德尔人的继承是指由两种异形的单一基因所控制的特性的继承,其中一种可能完全主导另一种。 孟德尔人的继承模式取决于这些特性是否由异体基因或性染色体基因所控制。 孟德尔人的继承模式取决于这些特性是否由异体基因或性染色体基因所控制。
      • Examples of human autosomal Mendelian traits include albinism and Huntington's disease. Examples of human X-linked traits include red-green color blindness and hemophilia.
        ::人类蛋白质蛋白质和亨廷顿病等人类蛋白质的个体蛋白质包括白化病和亨廷顿病,与人类X相关的特征包括红绿色失明和血友病。

      ::人类蛋白质蛋白质和亨廷顿病等人类蛋白质的个体蛋白质包括白化病和亨廷顿病,与人类X相关的特征包括红绿色失明和血友病。
    • Two tools for studying inheritance are pedigrees and Punnett squares. A pedigree is a chart that shows how a trait is passed from generation to generation. A Punnett square is a chart that shows the expected ratios of possible genotypes in the offspring of two parents.
      ::研究继承的两个工具是小儿科和Punnett 方块。小儿科是一张图表,显示一个特质如何代代相传。Punnett 方块是一张图表,显示双亲后代中可能基因型的预期比率。
    • Non-Mendelian inheritance refers to the inheritance of traits that have a more complex genetic basis than one gene with two alleles and complete dominance.
      ::非endelian继承是指具有比一个基因更复杂的遗传基础的遗传特征的继承,该基因有两个异系和完全占支配地位。
      • Multiple allele traits are controlled by a single gene with more than two alleles. An example of a human multiple allele trait is ABO blood type.
        ::多重异长特性由两个以上异长基因的单一基因控制。 人类多个异长特性的一个例子是ABO血型。
      • Codominance occurs when two alleles for a gene are expressed equally in the phenotype of heterozygotes. A human example of codominance occurs in the AB blood type, in which the I A  and I B  alleles are codominant.
        ::当一种基因的两个异象在异体zygots的苯型中以等同的表达方式表示时,就会出现共性。 在AB血型中出现人类的共性例子,在AB血型中,IA和IB异象是共性。
      • Incomplete dominance is the case in which the dominant allele for a gene is not completely dominant to a recessive allele, so an intermediate phenotype occurs in heterozygotes who inherit both alleles. A human example of incomplete dominance is Tay Sachs disease, in which heterozygotes produce half as much functional enzyme as normal homozygotes.
        ::完全占支配地位的情况是,基因的主宰异端并不完全占支配地位,因此,一种中间苯型出现在继承这两种异端的异体中。 人类不完全占支配地位的一个例子是Tay Sachs病,在这种疾病中,异端异端会产生功能性酶,其数量是正常同系物的一半。
      • Polygenic traits are controlled by more than one gene, each of which has a minor additive effect on the phenotype. This results in a continuum of phenotypes. Examples of human polygenic traits include skin color and adult height. Many of these types of traits, as well as others, are affected by the environment, as well as by genes.
        ::多基因特征由一个以上基因控制,其中每种基因都对苯型具有微小的添加效应,从而产生一系列苯型,人类多基因特征的例子包括肤色和成年身高,许多这类特征以及其它特征都受到环境以及基因的影响。
      • Pleiotropy refers to the situation in which a gene affects more than one phenotypic trait. A human example of pleiotropy occurs with sickle cell anemia, which has multiple effects on the body.
        ::Pleiotropy指一种基因影响不止一种胎儿特征的情况,人类的性激素例与镰状细胞贫血发生,对身体产生多重影响。
      • Epistasis is when one gene affects the expression of other genes. An example of epistasis is albinism, in which the albinism mutation negates the expression of skin color genes.
        ::Epistasisis是当一种基因影响其他基因的表达时。 癫痫的一个例子是白化,白化突变否定了肤色基因的表达。

      ::单基因控制着多个异变特性。 人类多重异变特性的示例是 ABO 血型。 当一种基因的两种异变基因在异性宫内同样表现在异体阳性球类中时, 就会出现常态。 AB 血型中会出现一种人类的共发异变特征, 即IA 和 IB 异变体具有共附性。 完全占支配地位的情况是, 基因的主导异变异性并不完全占居于静态异变异变异变的主导性, 因此在继承两种异种的异变异种中会出现一种中间异变异体。 一个人类的异变异性基因异变变异性的例子就是皮肤色和成年高。 Tay Sachs 疾病是人类不完全支配的异变异变异体, 其中, 异变异变变异性变异性基因变异体的变异性会比其他基因变异性, 其变异性会比其他基因变异性变异。
    • Genetic disorders are diseases, syndromes, or other abnormal conditions that are caused by mutations in one or more genes or by chromosomal alterations.
      ::遗传疾病是指一种或多种基因突变或染色体改变引起的疾病、综合症或其他异常情况。
      • Examples of genetic disorders caused by single-gene mutations include Marfan syndrome (autosomal dominant), sickle cell anemia (autosomal recessive), vitamin D-resistant rickets (X-linked dominant), and hemophilia A (X-linked recessive). Very few genetic disorders are caused by dominant mutations because these alleles are less likely to be passed on to successive generations.
        ::单基因突变引起的遗传障碍的例子包括:马凡综合症(黄素占多数)、镰状细胞贫血(黄素消退)、抗维他命D抗性(X-连带主导)和血友病A(X-连带休眠),很少有遗传障碍是主要突变造成的,因为这些异象不太可能传给后代。
      • Nondisjunction is the failure of replicated chromosomes to separate properly during meiosis. This may result in genetic disorders caused by abnormal numbers of chromosomes. An example is Down syndrome, in which the individual inherits an extra copy of chromosome 21. Most chromosomal disorders involve the X chromosome. An example is Klinefelter's syndrome (XXY, XXXY).
        ::非相容性是指复制的染色体在梅氏病期间未能适当分离,这可能导致染色体数量异常造成的遗传障碍,例如唐氏综合症,其中个人继承了另外一份染色体21。大多数染色体紊乱都涉及X染色体。Klinefelter综合症(XXY,XXXY)就是一个例子。
      • Prenatal genetic testing (by amniocentesis, for example) can detect chromosomal alterations in utero . The symptoms of some genetic disorders can be treated or prevented. For example, symptoms of phenylketonuria (PKU) can be prevented by following a low-phenylalanine diet throughout life.
        ::产前遗传检测(例如,通过氨基血清检测)可以检测出子宫的染色体变化,某些遗传障碍的症状可以治疗或预防,例如,苯丙酮尿(PKU)的症状可以通过在整个生命中采用低苯丙烯饮食来预防。
      • Cures for genetic disorders are still in the early stages of development. One potential cure is gene therapy, in which normal genes are introduced into cells by a vector such as a virus to compensate for mutated genes.
        ::基因紊乱的症候仍处于早期发育阶段,一种潜在的解药是基因疗法,在这种疗法中,正常基因由病毒等媒介引入细胞,以弥补变异基因。

      ::单基因突变引起的遗传障碍的例子有:马凡综合症(美甲主要病)、镰状细胞贫血(美甲消化)、抗维生素D抗性硬性激素(X-链接主导症)和血友病A(X-连接消化素),很少有遗传障碍是由支配性突变引起的,因为这些虫子不太可能传给后代。不相干是复制的染色体在梅氏病期间无法适当分离。这可能导致染色体数量不正常造成的遗传障碍。一个例子是唐氏综合症,其中个人继承了一种额外的染色体。21 多数染色体紊乱涉及Xromocome。一个例子是Klinefelter综合症(XXY,XXXY)。产前基因测试(例如通过免疫中心)可以检测出子宫内的染色体变异异。一些遗传病的症状可以治疗或预防。例如,苯丙胺细胞(PKU)的症状可以继承一种额外的染色体综合症,其中个人继承一种额外的染色体,21 多数染色体紊乱症涉及X-染色体;一个例子是Klinefelter综合综合症(通过基因系的基因疗法在基因的早期的基因治疗中可以预防生命中的早期中防止基因病变)。
    • Genetic engineering  is the use of technology to change the genetic makeup of living things for human purposes.
      ::遗传工程是利用技术改变人类生物的遗传构成。
      • Genetic engineering  methods include gene cloning and the polymerase chain reaction. Gene cloning is the process of isolating and making copies of a DNA segment, such as a gene. The polymerase chain reaction makes many copies of a gene or other DNA segment.
        ::遗传工程方法包括基因克隆和聚合酶链反应,基因克隆是分离和复制基因等DNA部分的过程,聚合酶链反应产生许多基因或其他DNA部分的复制品。
      • Genetic engineering  can be used to transform bacteria so they are able to make human proteins, such as insulin. It can also be used to create transgenic crops, such as crops that yield more food or resist insect pests.
        ::遗传工程可以用来改造细菌,以便它们能够制造人类蛋白质,如胰岛素,也可以用来制造转基因作物,如产生更多食物或抗虫害的作物。
      • Genetic engineering  has raised a number of ethical, legal, and social issues including health, environmental, and privacy concerns.
        ::遗传工程引起了一些伦理、法律和社会问题,包括健康、环境和隐私问题。

      ::遗传工程方法包括基因克隆和聚合酶链反应。基因克隆是分离和复制基因等DNA片段的过程。聚合酶链反应使基因或其他DNA片段有许多复制件。遗传工程可以用来改造细菌,使其能制造胰岛素等人类蛋白质。遗传工程也可以用来制造转基因作物,如产生更多食物或抵抗昆虫虫害的作物。遗传工程引起了一些伦理、法律和社会问题,包括健康、环境和隐私问题。
    • The human genome refers to all of the DNA of the human species. It consists of more than 3.3 billion base pairs divided into 20,500 genes on 23 pairs of chromosomes.
      ::人类基因组是指人类的所有DNA,由33亿对基对组成,在23对染色体上分为20,500个基因和23对染色体。
    • The Human Genome Project (HGP) was a multi-billion dollar international research project that began in 1990. By 2003, it had sequenced and mapped the location of all of the DNA base pairs in the human genome. It published the results as a human reference genome that is available to anyone on the Internet.
      ::人类基因组项目(人基因组项目)是1990年开始的耗资数十亿美元的国际研究项目,到2003年,该项目对人类基因组中所有DNA基对的位置进行了排序和绘图,并将结果作为人类参考基因组公布,供任何人在因特网上查阅。
    • Sequencing of the human genome is helping researchers better understand cancer and genetic diseases. It is also helping them tailor medications to individual patients, which is the focus of the new field of pharmacogenomics. In addition, it is helping researchers better understand human evolution.
      ::人类基因组的分级有助于研究人员更好地了解癌症和遗传疾病,还帮助他们为个别病人量身定制药物,这是新药理学领域的重点,此外,还有助于研究人员更好地了解人类进化。

    Now you know how traits are passed down through generations and how genetic variability can be generated through sexual reproduction and mutations. These concepts are critical for the understanding of evolution, which you will learn about in the next chapter.
    ::现在,你知道性特征是如何传承代代相传的,以及如何通过性繁殖和突变产生基因变异。这些概念对于理解进化至关重要,将在下一章中学习。

    Chapter Summary Review
    ::" 概述 " 章次

    1. Put the following units in order from the smallest to the largest:
    ::1. 将下列单位从最小单位改为最大单位:

    chromosome; gene; nitrogen base; nucleotide; codon
    ::染色体; 基因; 氮基; 核酸; codon

    2. Put the following processes in the correct order of how a protein is produced, from earliest to latest:
    ::2. 将下列过程按照蛋白质如何生产的正确顺序,从最早到最晚:

    (1) tRNA binding to mRNA; (2) transcription; (3) traveling of mRNA out of the nucleus; (4) folding of the polypeptide
    :伤心1) tRNA 与 mRNA 捆绑的 tRNA; (2) 转录; (3) mRNA 从核体外旅行; (4) 聚极化物折叠

    3. Which sentence is correct?
    ::3. 哪个句子正确?

    a. Different alleles of the same gene are located at the same locus on homologous chromosomes.
    ::a. 同一基因的不同异源位于同族染色体的同一极点。

    b. Different alleles of the same gene are located at different loci on homologous chromosomes.
    ::b. 同一基因的不同异源位于同族染色体的不同地点。

    c. Different genes of the same alleles are located at the same locus on homologous chromosomes.
    ::c. 同一异系染色体的同一极点有同一异系异系不同基因。

    d. Different alleles of the same gene are located at different loci on the same chromosome.
    ::d. 同一基因的不同异源位于同一染色体的不同地点。

    4. What are the differences between a sequence of DNA and the sequence of mature mRNA that it produces?
    ::4. DNA序列与其产生的成熟的MRNA序列之间有什么区别?

    5. Scientists sometimes sequence DNA that they “reverse transcribe” from the mRNA in an organism’s cells, which is called complementary DNA (cDNA). Why do you think this technique might be particularly useful for understanding an organism’s proteins versus sequencing the whole genome (i.e. nuclear DNA) of the organism?
    ::5. 科学家有时会排序他们 " 反向转录 " 的DNA,从一个生物细胞中 " 转录 " 的MRNA,即所谓的互补DNA(cDNA),为什么你认为这种技术对于了解一个生物的蛋白质和测算整个生物基因组(即核DNA)的顺序特别有用?

    6. A person has a hypothetical Aa genotype. Answer the following questions about this genotype:
    ::6. 一个人有一个假想的Aa基因型,回答关于这个基因型的下列问题:

    a. What do A and a represent?
    ::a. A和a代表什么?

    b. If the person expresses only the phenotype associated with A , is this an example of complete dominance, codominance, or incomplete dominance? Explain your answer. Also, describe what the observed phenotypes would be if it were either of the two incorrect answers.
    ::b. 如果该人只表示与A有关的苯型,这是完全支配地位、共占或不完全支配地位的例子吗?解释你的答复。此外,请说明如果是两种不正确的答案之一,观察到的苯型将是什么。

    7. Explain how a mutation that occurs in a parent can result in a genetic disorder in their child. Be sure to include which type of cell or cells in the parent must be affected in order for this to happen.
    ::7. 解释父母中发生的突变如何导致子女遗传紊乱,确保包括父母中的哪一类细胞或细胞必须受到影响才能发生。

    8. What is the term for an allele that is not expressed in a heterozygote?
    ::8. 异体兹哥特未用异体兹哥特表示的异形方言,其用词是什么?

    9. Proteins are made in the cytoplasm on small organelles called ___________ .
    ::9. 蛋白质在称为的小有机物的细胞托盘上制造。

    10. True or False:  Sex is determined by a gene on an autosome.
    ::10. 真实或虚假:性是由体形上的基因决定的。

    11 . True or False:  In sexual reproduction, parents and offspring are never identical.
    ::11. 真实或虚假:在性生殖方面,父母和子女从来就不一样。

    12. True or False:  In humans, a gamete will have 23 chromosomes.
    ::12. 真实或假:在人类中,网友将拥有23种染色体。

    13. True or False:  The expression of an organism’s phenotype produces its genotype.
    ::13. 真实或假:一个生物体的苯型的表达方式产生其基因型。

    14. True or False:  Meiosis is involved in the production of egg cells in humans.
    ::14. 真实或假:在人类生产蛋细胞时涉及美思病。

    15. True or False:  It is entirely likely for a gene to have more than two alleles.
    ::15. 真实或假:基因极有可能具有两个以上相位数。

    16. True or False:  Initiation of transcription occurs when the enzyme (DNA polymerase) binds to the promoter of a gene.
    ::16. 真实或假的:当酶(DNA聚合酶)与基因促进者结合时,即开始转录。

    17. What might happen if codons encoded for more than one amino acid?
    ::17. 如果codon为不止一种氨基酸编码,会发生什么情况?

    18. Mendel’s law of independent assortment states that
    ::18. 门德尔的独立的各类人法规定:

    a. Two factors of the same characteristic separate into different gametes.
    ::a. 同一特点的两个因素分别分为不同的调子。

    b. There are dominant and recessive factors.
    ::b. 有支配性和暂时性因素。

    c. Factors controlling different characteristics are inherited independently of each other.
    ::c. 控制不同特性的因素是相互独立继承的。

    c. There are two factors that control inheritance.
    ::c. 有两个因素可以控制遗产继承。

    19. A silent point mutation codes for the same _______ _______ as the original gene.
    ::19. 与原始基因相同的无声点突变编码。

    20. Explain why a human gene can be inserted into bacteria and can still produce the correct human protein, despite being in a very different organism.
    ::20. 解释为什么人类基因可以插入细菌,并且仍然可以产生正确的人类蛋白质,尽管它处在一个完全不同的有机体中。

    21. Linked genes...
    ::21. 连接基因. . . .

    a. are on homologous chromosomes
    ::a. 在同族染色体上

    b. are on the same chromosome
    ::b. 在同一染色体上

    c. are on adjacent chromosomes
    ::c. 相邻染色体上的染色体

    d. are on non-homologous chromosomes
    ::d. 在非血色染色体上。

    22. Something in the environment that can cause a mutation is called a __________ .
    ::22. 环境中某些可引起突变的东西被称为___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

    23. True or False:  All of your genes are expressed by all the cells of your body.
    ::23. 真实或假:你的所有基因都由你身体的所有细胞表示。

    24. Which of the following increase genetic variation:
    ::24. 下列哪一种增加遗传变异:

    a. mutations
    ::a. 变异

    b. crossing-over during meiosis
    ::b. 流行病期间跨越过境点

    c. sexual reproduction
    ::c. 性生殖

    d. all of the above
    ::d. 以上所有情况

    25. A woman has red-green color blindness, which is an X-linked recessive trait. Her husband does not have red-green color blindness. Which of the following is correct?
    ::25. 妇女有红绿色失明,这是与X有关的休眠特征,丈夫没有红绿色失明,以下哪一种正确?

    a. Half of their daughters will have red-green color blindness.
    ::a. 半数女儿将失明红绿色。

    b. All of their daughters will have red-green color blindness.
    ::b. 所有女儿都将失明红绿色。

    c. All of their sons will have red-green color blindness.
    ::c. 其所有儿子都将失明红绿色。

    d. All of their children will have red-green color blindness.
    ::d. 所有子女都将失明红绿色。

    26. Which of the following is an example of Mendelian inheritance?
    ::26. 以下哪些是门德利人继承遗产的例子?

    a. a trait that has three alleles
    ::a. 具有三个等同特性的特性

    b. a trait that is controlled by two genes
    ::b. 由两个基因控制的特性

    c. a trait that is controlled by a single gene with one dominant and one recessive allele
    ::c. 由单一基因控制的特性,该基因具有一种支配性和一种闭合性异性。

    d. a trait that has two alleles, both of which are expressed equally in the phenotype
    ::d. 具有两种异差的特性,两种异差均以苯型表示等同。

    27. What is gene therapy?  Why is gene therapy considered a type of biotechnology?
    ::27. 什么是基因疗法?为什么基因疗法被视为一种生物技术?

    28. The central dogma of molecular biology essentially describes how ____________ are made.
    ::28. 分子生物学的中心教条基本上描述了如何制造。