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  • 案例研究结论 - 您的基因可以帮助您拯救生命

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    Case Study Conclusion: Your Genes May Help You Save a Life
    ::案例研究结论:你的基因可以帮助你拯救生命

    As you have learned in this chapter, humans are much more genetically similar to each other than they are different. Any two people on Earth are 99.9 percent genetically identical to each other — but the mere 0.1 percent that is different can be very important, as in the case of bone marrow donation to treat diseases such as leukemia. A good match must exist between a bone marrow donor and recipient in genes that encode for human leukocyte antigen (HLA) proteins. As you have learned, antigens are molecules — often on the surface of cells — that the immune system uses to identify foreign invaders. If a patient receives a bone marrow transplant from a donor that has different types of HLAs than the patient does, antibodies in their immune system will identify the antigens as nonself and will launch an attack on the transplanted cells. Also, since bone marrow produces immune cells, antibodies in the transplanted tissue can actually attack the patient’s own cells using  the same mechanism. 
    ::正如你们在本章中所学到的,人类在基因上比异。地球上的任何一个人都具有99.9%的遗传特征 — — 但只有0.1%的差异可能非常重要,比如用骨髓捐赠治疗白血病等疾病。 骨髓捐赠者与接受者之间必须存在良好的匹配,这些基因是人类白血球抗原蛋白的编码。 正如你们所知道的,抗原是细胞表面的分子 — — 通常在细胞表面 — — 免疫系统用来识别外来入侵者。 如果病人从捐赠者那里得到骨髓移植,而捐赠者与病人不同种类的HLA进行移植,那么其免疫系统中的抗体将确认抗原为非自身,并将对移植细胞发起攻击。 此外,由于骨髓产生免疫细胞,移植组织中的抗体实际上可以使用同样的机制攻击病人自己的细胞。

    As you have also learned, a good HLA match is often difficult to find, even between full siblings. Every year, about 14 thousand people in the United States must try to find a compatible donor from a bone marrow registry. These registries store information on HLA type from potential donors, like the woman shown above. It can take months or years to find a compatible match — if one is found at all.
    ::如你所知,即使完全的兄弟姐妹之间也往往难以找到良好的HLA匹配,每年,美国大约有14 000人必须设法从骨髓登记册中找到一个兼容的捐赠者,这些登记册储存潜在捐赠者(如上述妇女)提供的HLA类型的信息,如果找到匹配者,可能需要数月或数年才能找到匹配者。

    Finding a match in the registries is particularly hard for non-Caucasian people — and even harder for people from multiethnic backgrounds, such as seven-year-old Tyler, who you read about in the beginning of this chapter. Tyler is of African, Japanese, and Caucasian descent — a relatively rare combination. Because HLA matches are more likely to occur between people of the same ethnicity, the donor registries would ideally have sufficient potential donors from every ethnicity and ethnic combination. Unfortunately, some ethnicities are not sufficiently represented in the donor registry. According to the U.S. National Marrow Donor Program, while 97 percent of Caucasian patients find a match, the match rate drops to 83 percent for Hispanic or Latino patients and 76 percent for African American or black patients. Multiethnic patients generally have an even harder time finding a match because the relative rareness of their particular ethnic combination in the general population makes it less likely that enough people of their same ancestry are registered donors.
    ::对于非高加索人来说,在登记簿中寻找匹配对于非高加索人来说尤为困难,对于多族裔背景的人来说则更为困难,例如7岁的泰勒,你在本章开头所读到的泰勒。泰勒是非洲人、日本人和高加索人后裔,这是一个相对罕见的组合。由于HLA的匹配更有可能发生在同一族裔的人之间,因此捐赠者登记册最好有足够的来自各个族裔和族裔组合的潜在捐赠者。不幸的是,一些族裔在捐赠者登记册中的代表性不足。 根据美国国家马罗捐助方案,虽然97%的高加索病人找到了匹配,但西班牙裔或拉丁裔病人的匹配率下降到83%,非裔或黑人病人的匹配率下降到76%。多族裔病人通常更难找到匹配,因为他们在普通人口中的特殊种族组合相对稀少,因此他们同一祖先的足够人口成为注册捐赠者的可能性更小。

    As you learned in this chapter, human variation has historically been classified in several different ways, some of which resulted from or have contributed to racism. Most biological traits in humans exist on a continuum, and attempting to create biological categories of race based on discrete categories using a handful of traits is generally arbitrary and inaccurate. Gene flow through migration and mating between populations, genetic drift, and natural selection results in a gradual, clinal distribution of many human traits, rather than discrete categories. Tyler, for example, cannot be neatly placed into one racial category or another. Race and ethnic identity, however, remain important social and cultural concepts. 
    ::正如你们在本章中所了解到的,人类变异历来以几种不同的方式分类,其中一些是种族主义造成的或促成种族主义的,人类的大多数生物特征是连续存在的,试图利用少数特征根据不同类别建立生物种族类别一般是任意和不准确的。 基因通过人口之间的移徙和交配、基因漂移和自然选择,导致许多人类特征的逐步、横向分布,而不是分立类别。例如,泰勒无法正确地归入一个或另一个种族类别,但种族和族裔特征仍然是重要的社会和文化概念。

    Tyler’s ancestry, however, does play a role in determining his specific types of HLA proteins, and he is more likely to find a bone marrow match with a donor of an ethnic background similar to his own. Although there is much more genetic variation within races than between races, HLA types tend to correlate with ethnicity more than some other traits. As you have seen throughout this chapter, some environmental factors in different geographic regions have provided strong natural selection pressures, resulting in the development of genetic differences between people whose ancestors came from different areas. For example, adaptations to differing UV levels, diseases, altitudes, and climates all likely led to the evolution of human variations in skin color, blood cells, and body morphology. This type of association between race and ethnicity and genetic variation is similar to the link between ethnicity and HLA type.
    ::然而,泰勒的祖先确实在确定他特定类型的HLA蛋白质方面扮演了一定的角色,而且他更有可能发现骨髓与类似他自己的种族背景的捐赠者相匹配。 尽管种族内部的遗传差异比种族之间要多得多,但HLA类型往往与族裔的关系比其他特征要多。 正如你在整个本章中所看到的那样,不同地理区域的一些环境因素造成了强烈的自然选择压力,导致祖先来自不同地区的人之间的遗传差异。 比如,适应不同的紫外线水平、疾病、高度和气候都可能导致人类在肤色、血细胞和身体形态方面的变化。 这种种族和族裔之间的联系和遗传差异类似于族裔和HLA类型之间的联系。

    Tyler’s family was not able to find a match for him in the bone marrow registries, but they are not giving up hope. His parents have started working with organizations to host bone marrow drives, where potential donors can provide cheek swabs to add themselves to the donor registry. His parents have contacted the news media with Tyler’s story, and family and friends are getting the word out on social media that more donors are needed, particular those with Tyler’s specific combination of ethnicities. They hope that even if they are unable to find a match for Tyler, bringing awareness to the issue may increase the ethnic diversity of the donor registry to save other lives.
    ::泰勒的家人无法在骨髓登记簿中找到匹配他的人,但他们并没有放弃希望。 他的父母已经开始与组织合作主办骨髓驱动器,在组织中潜在捐赠者可以提供脸颊擦拭以加入捐赠者登记册。 他的父母已经与新闻媒体联系泰勒的故事,而家人和朋友正在社交媒体上听到消息说需要更多的捐赠者,特别是泰勒特有的种族组合。 他们希望即使他们找不到与泰勒的匹配,但提高对这一问题的认识可能会增加捐赠者登记册的种族多样性以拯救其他生命。

    You Can Help!
    ::你可以帮忙! You can help!

    According to the U.S. Department of Health and Human Services, more donors are needed to join the bone marrow registry, particularly people from the following backgrounds:
    ::据美国卫生与公众服务部称,需要有更多的捐助者加入骨髓登记册,特别是来自以下背景的人:

    • Black or African American
    ::• 黑人或非裔美国人

    • Hispanic or Latino
    ::· 西班牙语或拉丁语

    • Asian
    ::• 亚洲

    • American Indian or Alaska Native
    ::• 美国印第安人或阿拉斯加土著人

    • Native Hawaiian or other Pacific Islander
    ::• 土著夏威夷人或其他太平洋岛民

    • People of multiple races or ethnicities
    ::• 多种族或多族裔人民

    Are you registered? If not, it is a relatively simple process that could save someone’s life. A cheek swab is all that is initially needed. Only about one in 430 potential donors will actually be matched with a patient, and if you are chosen, it means that you are one of the only people on Earth who can donate to this patient because of your genetic similarity! If you decide to donate, bone marrow will either be surgically removed from the back of your pelvic bone, or blood-forming cells will be removed non-surgically from your bloodstream. Most donors are able to return to their normal activities one to seven days after donation — a small price to pay for potentially saving someone’s life! 
    ::你是否注册了?如果不是的话,这是一个相对简单的过程,可以拯救某人的生命。最初需要的只是脸部擦拭。 430个潜在捐赠者中只有大约1个能够真正与病人匹配,如果你被选中,这意味着你是唯一能够因你的基因相似性而向病人捐赠的人之一!如果你决定捐赠,骨髓就会被切除,否则血造细胞就会被从你的血液中除去。 大多数捐赠者能够在捐赠后一到七天恢复正常活动 — — 这是拯救某人生命的一小部分代价!

    Watch this video to find out more about the donation process and to hear experiences of actual donors.
    ::以了解更多捐赠过程, 并了解实际捐赠者的经验。

    Chapter Summary
    ::章次摘要

    In this chapter, you learned about human variation and its origins. Specifically, you learned that:
    ::在本章中,你学会了人类的变异及其起源。具体地说,你学到了:

    • No two human individuals are genetically identical (except for monozygotic twins), but the human species as a whole exhibits relatively little genetic diversity relative to other mammalian species. Genetically, two people chosen at random are likely to be 99.9 percent identical.
      ::与其他哺乳动物物种相比,人类的基因多样性相对较少。 在遗传学上,随机选择的两个人可能达到99.9%。
    • Of the total genetic variation in humans, about 90 percent occurs between people within continental populations, and only about 10 percent occurs between people from different continents. Older, larger populations tend to have greater genetic variation, because there's been more time and there are more people in which to accumulate mutations. 
      ::在人类的全部基因变异中,大约90%发生在大陆人口之间,只有大约10%发生在不同大陆的人之间。 年龄较大的人口往往有更大的基因变异,因为有更多的时间和更多的人可以积累突变。
    • Single nucleotide polymorphisms account for most human genetic differences. Allele frequencies for polymorphic genes generally have a clinal, rather than discrete, distribution. A minority of alleles seem to cluster in particular geographic areas, such as the allele for no antigen in the Duffy blood group. Such alleles may be useful as genetic markers to establish the ancestry of individuals.
      ::单核素化多形态的单一核素化是人类基因差异最大的因素。 多形态基因的异变频率一般具有分泌性而不是分泌性分布。少数异变频似乎聚集在特定地理区域,如Duffy血族中无抗原的异变。这些异变可能作为基因标记对确定个人祖先有用。
    • Knowledge of genetic variation can help us understand our similarities and differences. It can also help us reconstruct our evolutionary origins and history as a species. For example, the distribution of modern human genetic variation is consistent with the out-of-Africa hypothesis for the origin of modern humans.
      ::基因变异的知识可以帮助我们理解我们的异同,也可以帮助我们重建我们作为一个物种的进化起源和历史。 比如,现代人类基因变异的分布符合非洲以外现代人类起源的假设。
    • An important benefit of studying human genetic variation is learning more about the genetic basis of human diseases. This should help us find more effective treatments and cures.
      ::研究人类基因变异的一个重要好处是更多地了解人类疾病的遗传基础,这将有助于我们找到更有效的治疗和治疗方法。
    • Humans seem to have a need to classify and label people based on their similarities and differences. Three approaches to classifying human variation are  typological, populational, and clinal approaches.
      ::人类似乎需要根据异同对人进行分类和标签。 人类变异的分类有三种方法,即类型学、人口学和临床方法。
      • The typological approach involves creating a system of discrete categories, or races. This approach was widely used by scientists until the early 20th century. Racial categories are based on observable phenotypic traits (such as skin color), but other traits and behaviors are often mistakenly assumed to apply to racial groups, as well. The use of racial classifications often leads to racism.
        ::类型学方法涉及建立一个由不同类别或种族组成的系统,直到20世纪初,这一方法一直被科学家广泛使用;种族分类基于可观测到的胎儿特征(如肤色),但其他特征和行为往往被错误地假定适用于种族群体,使用种族分类往往导致种族主义。
      • By the mid-20th century, scientists started advocating a population approach. This assumes that the breeding population, which is the unit of evolution, is the only biologically meaningful group. While this approach makes sense in theory, in reality, it can rarely be applied to actual human populations. With few exceptions, most human populations are not closed breeding populations.
        ::到20世纪中叶,科学家开始倡导人口方法。 这假定繁殖人口是进化的单位,是唯一具有生物意义的群体。 虽然这种方法在理论上是有道理的,但实际上很少能适用于实际的人类人口。 除了少数例外,大多数人类人口不是封闭的繁殖人口。
      • By the 1960s, scientists began to use a clinal approach to classify human variation. This approach maps variation in the frequency of traits or alleles over geographic regions or worldwide. Clinal maps for many genetic traits show variation that changes gradually from one geographic area to another. Gene flow and/or natural selection can cause this type of distribution.
        ::到1960年代,科学家开始使用临床方法对人类变异进行分类,该方法绘制了不同地理区域或世界范围内的特性或异象频率的变化图,许多遗传特性的临床图显示,从一个地理区域逐渐变化到另一个地理区域的变异图。基因流动和/或自然选择可能导致这种类型的分布。

      ::类型学方法涉及建立一个由不同类别或种族组成的系统。 这种方法在20世纪初之前一直被科学家广泛使用。 种族类别基于可见的胎儿特征(如肤色),但其他特征和行为往往被错误地假定适用于种族群体。 种族分类的使用往往导致种族主义。 到20世纪中叶,科学家开始倡导人口方法。 这假定繁殖人口(即进化单位)是唯一具有生物意义的群体。 虽然这种方法在理论上是有道理的,但实际上很少适用于实际的人类人口。除了少数例外,大多数人类人口不是封闭的繁殖人口。 到1960年代,科学家开始使用一种直线方法来对人类变异进行分类。这种方法绘制了地理区域或世界范围内的特性或所有要素的频率变化图。许多遗传特征的Clinal地图显示从一个地理区域到另一个地理区域的变异。基因流和/或自然选择可以造成这种类型的分布。
    • Humans may respond to environmental stress in four different ways: adaptation, developmental adjustment, acclimatization, and cultural responses.
      ::人类可以通过四种不同的方式应对环境压力:适应、发展调整、适应、适应和文化应对。
      • An adaptation is a genetically based trait that has evolved because it helps living things survive and reproduce in a given environment. Adaptations evolve by natural selection in populations over a relatively long period to time. Examples of adaptations include sickle cell trait as an adaptation to endemic malaria and the ability to taste bitter compounds as an adaptation to bitter-tasting toxins in plants.
        ::适应是一种遗传特征,它已经演变,因为它有助于生物在特定环境中生存和繁殖。适应随着人口在相当长的一段时间里自然选择而演变。 适应的例子包括镰状细胞特性作为地方性疟疾的适应,以及能够尝苦性化合物作为植物中苦性毒素的适应。
      • A developmental adjustment is a nongenetic response to stress that occurs during infancy or childhood. It may persist into adulthood and may be irreversible. Developmental adjustment is possible because humans have a high degree of phenotypic plasticity. It may be the result of environmental stresses, such as inadequate food — which may stunt growth — or cultural practices, such as orthodontic treatments, which re-align the teeth and jaws.
        ::发育调整是对婴儿或童年时期产生的压力的非遗传反应,它可能持续到成年,并且可能是不可逆转的;发育调整是可能的,因为人类具有很高的雌性可塑性;可能是由于环境压力造成的,例如食物不足——这可能阻碍成长——或诸如矫正牙牙和下巴的矫正等文化习俗。
      • Acclimatization is the development of reversible changes to environmental stress that develop over a relatively short period of time. The changes revert to the normal baseline state after the stress is removed. Examples of acclimatization include tanning of the skin and physiological changes (such as increased sweating) that occur with heat acclimatization.
        ::适应性化是指在相对较短的时间内发展出对环境压力的可逆变化,这些变化在消除压力后恢复到正常基线状态,适应性化的例子包括皮肤晒黑和热化后产生的生理变化(如出汗增加)。
      • Cultural responses consist of learned behaviors and technology that allow us to change our environment to control stress, rather than changing our bodies genetically or physiologically to cope with stress. Examples include using shelter, fire, and clothing to cope with a cold climate.
        ::文化反应包括学习到的行为和技术,使我们能够改变环境以控制压力,而不是在基因上或生理上改变身体以应对压力。 例子包括利用住所、火灾和衣服来应对寒冷的气候。

      ::适应是一种遗传特征,因为它有助于生活物在特定环境中生存和繁殖,因此是一种演变的遗传特征。适应随着人口在相当长的时期内自然选择而演变。适应的例子包括:镰状细胞特征,作为地方性疟疾的适应,以及作为植物中苦性毒素的适应而尝苦性化合物的能力。发育调整是对婴儿或童年时期产生的压力的非遗传反应,它可能持续到成年,并且可能是不可逆转的。发育调整是可能的,因为人类具有高度的细微可塑性而有可能发生。它可能是环境压力的结果,例如食物不足——这可能阻碍成长——或文化习俗,例如牙牙和下部重新调和牙牙牙的牙牙治疗等。发育调整是指在相对较短的时间内发展出对环境压力的可逆性变化。在消除压力之后,变化会恢复到正常的基准状态。进化的例子包括皮肤和生理变化(例如汗量增加)随着热化而发生的环境压力——例如,食物不足——可能阻碍成长——或诸如牙和下牙合牙合牙的治疗等文化习俗。适应能力是发展出在较短的时期内对环境压力的可逆性变化。文化反应,包括我们学习和生理压力的适应环境的适应。我们学会反应,包括学会反应,我们学会反应,我们学会反应,包括了变化,我们学会反应,以及适应环境的适应环境,我们学会反应,包括了变化,包括了我们学会反应,我们学会反应,我们学会反应,我们学会反应,我们学会性反应到的习惯反应,包括了变化,我们适应。 以及适应了变化的习惯性反应。
    • Human skin color is correlated with the intensity of solar radiation. This produces a clinal distribution in skin color, with the darkest skin found near the equator and lighter skin found at increasing latitudes.
      ::人类皮肤颜色与太阳辐射强度相关,产生皮肤颜色的阴道分布,在赤道附近发现最暗的皮肤,在不断升高的纬度上发现较轻的皮肤。
    • Human skin color is determined mainly by a pigment called melanin. Most of the variation in skin color is due to differences in the amount of melanin that is produced in the skin.
      ::人类的肤色主要是由一种称为美兰素的色素决定的,肤色的变化大多是由于皮肤产生的美兰素数量的差异。
      • Melanin is produced in skin cells called melanocytes located at the bottom of the outer layer of skin (epidermis). Within melanocytes, organelles called melanosomes synthesize melanin. They also store and transport the melanin to other epidermal cells, where the melanin absorbs UV light and prevents it from causing damage.
        ::在皮肤外层底部的皮肤细胞中产出梅兰宁,称为梅兰宁,在皮肤外层底部的皮细胞中产出梅兰尼,在黑兰尼的皮肤细胞中,称为黑兰尼的有机物合成了美兰尼,它们还储存和将梅兰尼运到其他上皮细胞,其中梅兰尼吸收紫外线,防止它造成破坏。
      • Both the type and amount of melanin are controlled by several genes with multiple alleles.
        ::甲状腺素的类型和数量都由多种蛋白的几种基因控制。

      ::米兰宁产于皮肤外层底部的皮肤细胞中,称为梅兰尼(melanocytes)的皮肤细胞中,位于皮肤外层底部(epidimis),在梅兰诺氏菌中,称为黑素的有机体合成了梅兰尼,它们还储存和将梅兰宁运到其他上皮细胞中,其中梅兰尼吸收紫外线,防止它造成损害。梅兰尼的种类和数量都由多种异性基因控制。
    • Dark skin evolved in human ancestors about 1.2 million years ago in Africa as an adaptation to UV radiation on hairless skin. Dark skin protects from DNA damage and skin cancer, as well as the destruction of folic acid, a B vitamin important in reproduction.
      • People who later left Africa for Europe and East Asia independently evolved light skin as an adaptation to lower levels of UV light. Lighter skin can synthesize more vitamin D than darker skin, thus reducing the risk of disorders like  osteoporosis and rickets. Some arctic people did not evolve very light skin as one might expect, because their traditional diet provided adequate vitamin D.
        ::后来离开非洲前往欧洲和东亚的人独立地将光皮肤演变为适应低紫外线光线的适应。 较轻的皮肤可以合成更多的维生素D而不是更深的皮肤,从而降低骨质疏松症和类等疾病的风险。 一些北极人没有像人们预期的那样发展出非常浅的皮肤,因为他们的传统饮食提供了足够的维生素D。

      ::在120万年前的非洲,人类祖先染色变黑,以适应无毛皮肤的紫外线辐射。 黑皮肤保护人们免受DNA损伤和皮肤癌以及叶酸(一种对生殖非常重要的维生素B)的破坏。 后来离开非洲前往欧洲和东亚的人将光皮肤独立演变为对低紫外光的适应。 较轻的皮肤可以合成更多的维生素D,而不是更深的皮肤,从而减少骨质疏松症和类等疾病的风险。 一些北极人没有像人们预期的那样发展出非常浅的皮肤,因为他们的传统饮食提供了足够的维生素D。
    • Tanning of the skin is an example of acclimatization to seasonal changes — in this case, to changes in UV radiation. It occurs when melanocytes detect UV light and produce more melanin in response.
      ::皮肤色素是适应季节性变化的一个例子——在本案中,适应紫外线辐射的变化,当甲状腺素检测紫外线光线并生产更多的美兰素时,就会出现这种情况。
    • After puberty, females generally have somewhat less melanin than males. This may reflect stronger natural selection for vitamin D-synthesizing ability, because of the greater vitamin D requirements during pregnancy and lactation.
      ::青春期后,女性的梅拉宁一般比男性少一些,这也许反映出维生素D合成能力的自然选择能力较强,因为怀孕和哺乳期间对维生素D的需求更大。
    • Blood type is a genetic characteristic associated with the presence or absence of antigens on the surface of red blood cells. A blood group system refers to all of the gene(s), alleles, and possible genotypes and phenotypes that exist for a particular set of blood type antigens.
      ::血型是一种遗传特征,与红细胞表面是否存在抗原有关,血组系统是指特定血型抗原中存在的所有基因、异象、可能存在的基因型和苯型。
      • Antigens are molecules that the immune system identifies as either self or nonself. If antigens are identified as nonself, the immune system responds by forming antibodies that are specific to the nonself antigens, leading to the destruction of cells bearing the antigens.
        ::抗原是免疫系统确定为自有或非自有的分子,如果抗原被确定为非自有,免疫系统的反应是形成非自有抗原特有的抗体,导致带有抗原的细胞被摧毁。

      ::抗原是免疫系统确定为自有或非自有的分子,如果抗原被确定为非自有,免疫系统的反应是形成非自有抗原特有的抗体,导致带有抗原的细胞被摧毁。
    • The ABO blood group system is a system of red blood cell antigens controlled by a single gene with three common alleles on chromosome 9. There are four possible ABO blood types: A, B, AB, and O. The ABO system is the most important blood group system in blood transfusions. People with type O blood are universal donors, and people with type AB blood are universal recipients.
      ::ABO血族系是一个红血细胞抗原系统,由单一基因控制,在染色体9上有三个常见的异差。 ABO血族有四种可能:A型、B型、AB型和O型。 ABO血族系是输血中最重要的血族系。 O型血族系是普遍捐赠者,ABB血族为普遍接受者。
    • The frequencies of ABO blood type alleles and blood groups vary around the world. The allele for the B antigen is least common, and blood type O is the most common. Evolutionary forces of founder effect, genetic drift, and natural selection are responsible for the geographic distribution of ABO alleles and blood types. For example, people with type O blood may be somewhat resistant to malaria, possibly giving them a selective advantage where malaria is endemic.
      ::ABO血型异源和血族的频率在世界各地各异。 B抗原的异源最不常见,而O的异源最普遍。 创建效应、遗传漂移和自然选择的进化力量对ABO血型和血型的地理分布负责。 例如,O型血型的人可能在一定程度上抗疟疾,在疟疾流行的地方,可能给他们选择性优势。
    • The Rhesus blood group system is a system of red blood cell antigens controlled by two genes with many alleles on chromosome 1. There are five common Rhesus antigens, of which antigen D is the most significant. Individuals who have antigen D are called Rh+, and individuals who lack antigen D are called Rh-. Rh- mothers of Rh+ fetuses may produce antibodies against the D antigen in the fetal blood, causing hemolytic disease of the newborn (HDN).
      ::Rhesus血族系系由两种基因控制的红色血细胞抗原系统,两种基因在染色体1上含有多种异象,五种普通Rhesus抗原,其中抗原D最为重要,有抗原D的人称为Rh+,缺乏抗原D的人称为Rh-Rh-Rh-Rh-Rh-Rh+胎儿的母亲可能会产生抗体,对抗胎儿血液中的D抗原,导致新生儿的血液疾病(HDN)。
    • The majority of people worldwide are Rh+, but there is regional variation in this blood group system. This variation may be explained by natural selection that favors heterozygotes for the D antigen, because this genotype seems to be protected against some of the neurological consequences of the common parasitic infection toxoplasmosis.
      ::全世界大部分人都是Rh+,但这种血族系统存在区域差异。 这种差异的原因可能是自然选择偏向于D抗原的异体,因为这种基因类型似乎受到保护,免受常见寄生虫感染过氧化性硬化症的某些神经学后果的影响。
    • Malaria is an infection of the red blood cells caused by protozoan parasites in the genus  Plasmodium.  The species  Plasmodium   falciparum  causes the most cases of malaria and is also the most deadly. Humans are hosts to the parasite, as are  Anopheles  mosquitoes, which are also vectors for malaria. They spread the pathogen  between human hosts. 
      • Symptoms of malaria include recurrent debilitating fevers, fatigue, vomiting, and headaches. Prevention efforts include reducing the risk of exposure to mosquito bites and the size of mosquito populations. There is no vaccine to prevent malaria, but the disease can be treated with a combination of drugs.
        ::疟疾的症状包括经常发病、疲劳、呕吐和头痛,预防工作包括减少蚊子咬伤的风险和蚊子人口数量,没有预防疟疾的疫苗,但这种疾病可以混合药物治疗。
      • Malaria is endemic in tropical and subtropical regions of the world. In 2015, there were 214 million cases of malaria worldwide, and an estimated 438 thousand deaths from malaria — mainly in Africa, and primarily in young children. Malaria causes not only excess early mortality, but also loss of fertility, making it a potent agent of natural selection.
        ::疟疾在世界热带和亚热带地区流行,2015年,全世界疟疾病例为2.14亿,疟疾死亡人数估计为43.8万,主要在非洲,主要在幼儿中,疟疾不仅造成过早死亡率过高,而且造成生育率丧失,使其成为自然选择的有力因素。

      ::疟疾是原生虫寄生虫在原虫疟原虫中引起的红细胞感染,恶性疟原虫是疟疾的最主要病原体,也是最致命的。人类是寄生虫的宿主,阿诺斐尔蚊子也是疟疾的媒介,也是疟疾的媒介。它们传播人体宿主之间的病原体。疟疾的症状包括反复出现的致弱热、疲劳、呕吐和头痛。预防努力包括减少蚊子咬伤的风险和蚊子人口的数量。没有预防疟疾的疫苗,但这种疾病可以混合药物治疗。疟疾在世界热带和亚热带地区流行。2015年,全世界有2.14亿疟疾病例,估计有43.8万人死于疟疾,主要在非洲,主要是幼儿。疟疾不仅导致过早死亡,而且导致生育力丧失,使其成为自然选择的有力因素。
    • Most Old World human populations with a long history of endemic malaria have evolved genetic adaptations to malaria parasites. Most of the adaptations are abnormalities of red blood cells or hemoglobin, the oxygen-carrying protein that is the principal component of red blood cells. The genetic adaptations also produce anemia in a portion of the populations where the adaptations are prevalent.
      ::具有长期疟疾地方病历史的多数老世界人类对疟疾寄生虫进行了基因改造,大多数适应是红血细胞或血红蛋白的异常现象,血红蛋白是红血细胞的主要成份,基因改造也使部分适应流行的人口产生贫血症。
      • Abnormal hemoglobins that confer resistance to malaria include hemoglobin S, hemoglobin C, and hemoglobin E. Thalassemia is an inherited anemia caused by another hemoglobin abnormality that also confers resistance to malaria.
        ::对疟疾产生抗药性的异常血红蛋白包括血红蛋白S、血红蛋白C和血红蛋白E。 血红蛋白贫血是一种遗传性贫血症,由另一种血红蛋白异常现象造成,也会导致对疟疾的抗药性。
      • Other red blood cell abnormalities that confer resistance to malaria include ovalocytosis, pyruvate kinase (PK) deficiency, glucose-6-phosphate dehydrogenase (G6PD) deficiency, and Duffy antigen negativity.
        ::其他导致抗疟疾的红细胞异常情况包括:卵巢细胞病症、气压动脉(PK)缺乏症、葡萄糖-6-磷酸盐脱氢酶(G6PD)缺乏症和Duffy抗原中性。

      ::对疟疾产生抗药性的异常血红蛋白包括血红蛋白S、血红蛋白C和血红蛋白E。 血红蛋白是一种遗传性贫血,由另一种血红蛋白异常导致,也导致对疟疾的抗药性。 其他导致对疟疾产生抗药性的红细胞异常包括卵巢细胞病、血压血清血清血清素(PK)缺乏、葡萄糖-6-磷酸盐脱氢酶(G6PD)缺乏和Duffy抗原神经性。
    • At high altitudes, humans face the stress of hypoxia, or a lack of oxygen. Hypoxia occurs at high altitude because there is less oxygen in each breath of air and lower air pressure, which prevents adequate absorption of oxygen from the lungs.
      • Initial responses to hypoxia include hyperventilation and elevated heart rate, but these responses are stressful to the body. Continued exposure to high altitude may cause high altitude sickness, with symptoms such as fatigue, shortness of breath, and loss of appetite. At higher altitudes, there is greater risk of serious illness.
        ::对缺氧的初步反应包括超通风和心率升高,但这些反应对身体造成压力。 继续高空接触可能导致高海拔疾病,症状如疲劳、呼吸短促和食欲丧失。 在高海拔地区,严重疾病的风险更大。
      • After several days at high altitude, acclimatization starts to occur in someone from a lowland population. More red blood cells and capillaries form, along with other changes . Full acclimatization may take several weeks. Returning to low altitude causes a reversal of the changes to the pre-high altitude state in a matter of weeks.
        ::在高海拔数天后,低地人口的某人开始进入适应状态。更多的红血细胞和刺绣形式以及其他变化。完全适应可能要花几个星期时间。回到低海拔状态会在几周内导致高地前状态变化的逆转。
      • Well over 100 million people live at altitudes higher than 2,500 meters above sea level. Some indigenous populations of Tibet, Peru, and Ethiopia have been living above 2,500 meters for thousands of years, and have evolved genetic adaptations to high altitude hypoxia.  Different high altitude populations have evolved different adaptations to the same hypoxic stress. Tibetan highlanders, for example, have a faster rate of breathing and wider arteries, whereas Peruvian highlanders have larger red blood cells and a greater concentration of the oxygen-carrying protein hemoglobin.
        ::西藏、秘鲁和埃塞俄比亚的一些土著居民数千年来一直生活在2,500米以上,并发展了适应高海拔缺氧的基因适应,不同的高海拔人口对同一缺氧压力的适应程度不同,例如西藏高地居民呼吸速度更快,动脉更宽,而秘鲁高地居民的红血细胞较多,含氧蛋白的血红蛋白浓度较高。

      ::在高地,人类面临缺氧或缺氧的压力。高海拔时出现缺氧,因为空气呼吸每口气氧量减少,空气压力降低,导致无法从肺部充分吸收氧气。对缺氧的初步反应包括超通风和心率升高,但这些反应对身体造成压力。继续接触高海拔可能导致高海拔疾病,症状如疲劳、呼吸不足和食欲丧失。在高地,严重疾病的风险更大。在高海拔几天后,低地人口开始出现血化现象。更多的红血细胞和心血管形式,加上其他变化。全面消化可能需要几周时间。回到低地可能使高度状态在数周内发生逆转。超过1亿人口生活在海拔2 500米以上的高度。西藏、秘鲁和埃塞俄比亚的一些土著人口在高海拔2 500米以上居住数千年,并逐渐对高海拔地的血基细胞进行遗传适应。不同高海拔的海拔人口比例和高海拔的氧浓度是更高的。不同的高海拔人口对高海拔水平进行了不同的适应,而高海拔的海拔和高海拔水平的海拔水平也具有更高的海拔压力。
    • Both hot and cold temperatures are serious environmental stresses on the human body. In the cold, there is risk of hypothermia, which is a dangerous decrease in core body temperature. In the heat, there is risk of hyperthermia, which is a dangerous increase in core body temperature.
      ::热温和冷温都是人体的严重环境压力。 在寒冷中,有低温的风险,这是核心体温的危险下降。 在热热中,有高温的风险,这是核心体温的危险上升。
    • According to Bergmann’s rule, body size tends to be negatively correlated with temperature, because larger body size increases heat production and decreases heat loss. The opposite holds true for small body size. Bergmann’s rule applies to many human populations that are hot or cold adapted.
      ::根据Bergmann的规则,身体体积往往与温度呈负相关关系,因为体积大会增加热量,减少热量损失。 体积小的情况正好相反。 Bergmann的规则适用于许多适应热度或冷度的人口。
    • According Allen’s rule, the length of body extremities is positively correlated with temperature, because longer extremities are better at dissipating excess body heat. The opposite applies to shorter extremities. Allen’s rule applies to relative limb lengths in many human populations that have adapted to heat or cold.
      ::根据艾伦的规则,体外体外长度与温度呈正比关系,因为更长的体外长度更能消散过度体热。 相反,更短的体外长度也适用。 艾伦的规则适用于许多适应热或冷的人群的相对四肢长度。
    • Sweating is the primary way humans lose body heat. The evaporation of sweat from the skin cools the body. This only works well when the relative humidity is fairly low. At high relative humidity, sweat does not readily evaporate to cool us down. The heat index (HI) indicates how hot it feels due to the humidity.
      ::汗水是人类失去体温的主要方式。 皮肤的汗水蒸发会冷却身体。 只有在相对湿度相当低的情况下, 汗水才会有效。 在较高的相对湿度下, 汗水不会轻易蒸发来冷却我们。 热指数(HI)表明湿度导致的热感。
    • Gradually working longer and harder in the heat can bring about heat acclimatization, in which the body has improved responses to heat stress. Sweating starts earlier, sweat contains less salt, and vasodilation brings heat to the surface to help cool the body. Full acclimatization takes up to 14 days and reverses just as quickly when the heat stress is removed.
      ::逐渐地在热中更长时间、更辛苦地工作,可以带来热加速化,使身体对热应力的反应得到改善。 更早地开始,汗水中含盐更少,血管通热会让表面变热,帮助体温。 完全加速化需要14天时间,在消除热应力时,反转速度同样快。
    • The human body can respond to cold by producing more heat (by shivering or increasing the basal metabolic rate) or by conserving heat (by vasoconstriction at the body surface or a layer of fat-insulating internal organs).
      ::人体可以通过产生更多热量(通过发抖或增加巴萨尔代谢速率)或通过保护热量(通过身体表面的血管收缩或一层脂肪隔热内器官)对寒冷作出反应。
    • At temperatures below freezing, the hunting response occurs to prevent cold injury (such as frostbite). This is a process of alternating vasoconstriction and vasodilation in extremities that are exposed to dangerous cold. Where temperatures are repeatedly cold but rarely below freezing, the hunting response may not occur, and the skin may remain cold due to vasoconstriction alone.
      ::在冰冻以下的温度下,狩猎反应是为了防止寒伤(如冻伤)而发生的,这是一种交替进行血管收缩和血管血管膨胀的过程,在面临危险寒冷的极端地区,这种过程是交替进行血管收缩和血管膨胀。 在温度反复寒冷但很少低于冰冷的地方,狩猎反应可能不会发生,而皮肤可能仅仅由于血管收缩而保持寒冷。
    • Milk contains the sugar lactose, a disaccharide. Lactose must be broken down into its two component sugars to be absorbed by the small intestine, and the enzyme lactase is needed for this process.
      • In about 60 percent of people worldwide, the ability to synthesize lactase and digest lactose declines after the first two years of life. These people become lactose intolerant, and cannot consume much milk without suffering symptoms such as bloating, cramps, and diarrhea.
        ::在世界上大约60%的人中,合成乳腺和消化乳糖的能力在生命的头两年后下降。 这些人变得不耐乳糖,不能在不患浮肿、抽搐和腹泻等症状的情况下消费大量牛奶。
      • In populations that herded milking animals for thousands of years, lactase persistence evolved. People who were able to synthesize lactase and digest lactose throughout life were strongly favored by natural selection. People who descended from these early herders generally still have lactase persistence. That includes many Europeans and European-Americans.
        ::在牛群挤奶数千年的人群中,乳酶的持久性不断演化。 能够合成乳酶和消化乳糖的人一生都受到自然选择的强烈青睐。 从这些早期牧民中下来的人通常仍然有乳酶的持久性。 其中包括许多欧洲人和欧洲裔美国人。

      ::乳糖含有甘蔗甘蔗, 一种分解法。 乳糖必须分解成两个组成部分的糖, 由小肠吸收, 这一过程需要酶乳酶。 在世界上大约60%的人中, 合成乳糖酶和消化乳糖的能力在生命的头两年过后会下降。 这些人变得不耐乳糖, 并且不能在不出现诸如浮肿、 抽搐和腹泻等症状的情况下大量消费牛奶。 在几千年来放牧哺乳动物的人群中, 乳糖持久性会演变。 能够合成乳糖酶和整个生命消化乳糖的人受到自然选择的极大青睐。 这些早期牧民的后代通常仍然具有乳糖持久性。 这包括许多欧洲人和欧裔美国人。
    • Human populations may vary in how efficiently they use calories in food. Some people (especially South Pacific Islanders, Native Americans, and sub-Saharan Africans) may be able to get by on fewer calories than would be adequate for others, so they tend to easily gain weight, become obese, and develop diseases such as diabetes.
      ::人类在食物中使用卡路里的效率可能各不相同。 一些人(特别是南太平洋岛民、美洲原住民和撒哈拉以南非洲人)的热量可能低于其他人的足够量,因此他们往往容易增加体重、肥胖和患糖尿病等疾病。
    • The thrifty gene hypothesis proposes that “thrifty genes” were selected for because they allowed people to use calories efficiently and store body fat when food was plentiful so they had a reserve to use when food was scarce. According to the hypothesis, thrifty genes become detrimental and lead to obesity and diabetes when food is plentiful all of the time.
      ::精密基因假设认为,选择“精密基因”是因为允许人们高效使用卡路里,在食物充足时储存体脂肪,从而在食物稀缺时拥有储备。 根据这一假设,节食基因会变得有害,导致肥胖和糖尿病,而食物充足时也会导致肥胖和糖尿病。
    • Several assumptions underlying the thrifty gene hypothesis have been called into question, and genetic research has been unable to actually identify thrifty genes. Alternate hypotheses to the thrifty gene hypothesis have been proposed, including the drifty gene hypothesis. The latter hypothesis explains variation in the tendency to become obese by genetic drift on neutral genes.
      ::自由基因假设背后的几种假设受到质疑,基因研究无法实际确定自由基因。 已经提出了对自由基因假设的替代假设,包括流基因假设。 后一种假设解释了中性基因遗传漂移导致肥胖趋势的变化。

    In this chapter, you learned about how genetic variation can lead to differences in human characteristics. Genes encode for proteins, which carry out our bodies’ life processes. In the next chapter, you will learn about how proteins and other molecules make up the cells, tissues, and organs of the human body, and how these units work together in interacting systems to allow us to function.
    ::在本章中,你学会了基因变异如何导致人类特性的差异。基因编码蛋白质,这些蛋白质会影响我们身体的生命过程。在下一章中,你会知道蛋白质和其他分子是如何组成细胞、组织和人体器官的,以及这些细胞单位如何在互动系统中共同工作,让我们得以运作。

    Chapter Summary Review
    ::" 概述 " 章次

    1. Explain why an evolutionarily older population is likely to have more genetic variation than a similarly-sized younger population.
    ::1. 解释为什么不断演变的老年人口的遗传变异可能大于年龄相似的年轻人口。

    2. The genetic difference between any two people on Earth is only about 0.1 percent. B ased on our evolutionary history, d escribe one reason why humans are relatively homogeneous genetically. 
    ::2. 地球上任何两个人之间的基因差异只有0.1%左右,根据我们的进化历史,说明了人类相对同质的遗传学原因之一。

    3. What aspect(s) of human skin color are due to adaptation? Be sure to define adaptation in your answer.  What aspect(s) of human skin color are due to acclimatization? Be sure to define acclimatization in your answer.
    ::3. 人类肤色的哪些方面因适应而引起? 请确定在您的答复中定义适应。 人类肤色的哪些方面因适应而引起? 请确定在您的答复中定义适应。

    4. For each of the following human responses to the environment, list whether it can be best described as an example of adaptation, acclimatization, or developmental adjustment:
    ::4. 对于下列每一种人类对环境的反应,请列出是否可以将其最好描述为适应、适应化或发展调整的例子:

    a. reduction in height due to lack of food in childhood
    ::a. 因童年缺乏食物而降低身高

    b. resistance to malaria
    ::b. 疟疾抗药性

    c. shivering in the cold
    ::c. 寒冷中颤抖

    d. changes in body size and dimensions to better tolerate heat or cold
    ::d. 改变身体大小和尺寸,以更好地忍受热或冷

    5. Give an example of a human response to environmental stress that involves changes in behavior, instead of changes in physiology.
    ::5. 举人类对环境压力的反应为例,这种压力涉及行为变化,而不是生理变化。

    6. What are two types of environmental stresses that caused genetic changes related to hemoglobin in some populations of humans?
    ::6. 造成某些人群中与血红蛋白有关的基因变化的两类环境压力是什么?

    7. True or False:  In general, people of European descent tend to have less genetic variation and more archaic human DNA than people of African descent.
    ::7. 真实或假:一般而言,欧洲裔人的基因变异程度较低,与非洲裔人相比,人类DNA更古老。

    8. True or False:  Air pressure is higher at higher altitudes.
    ::8. 真实或假:高空的空气压力较高。

    9. True or False:  The distribution of where fat is deposited in the body can be a response to climate.
    ::9. 真实或假:脂肪沉积在体内的分布可以作为对气候的一种反应。

    10. True or False:  There is only one blood group system in humans.
    ::10. 真实或假:人类只有一个血族系统。

    11. What has been the most rapid, phenotypically observable example of evolution in humans?
    ::11. 人类进化方面最迅速、最能见人性的典型例子是什么?

    12. The ability of an organism to change their phenotype in response to the environment is called phenotypic __________ .
    ::12. 生物体因应环境而改变其苯型的能力称为胸腔。

    13. ________ may have evolved, in part, to protect the body’s folic acid levels, while ________ may have evolved, in part, to protect vitamin D levels.
    ::13. 部分是为了保护身体叶酸水平而演变的,部分是为了保护维生素D水平而演变的。

    a. light skin; dark skin
    ::a. 浅皮肤;深皮肤

    b. dark skin; light skin
    ::b. 深皮肤;浅皮肤

    c. normal hemoglobin; hemoglobin S
    ::c. 正常血红蛋白;血红蛋白 S

    d. hemoglobin S; normal hemoglobin
    ::d. 血红蛋白S;正常血红蛋白

    14. List four natural selection pressures that differ geographically across the world and  contributed to the evolution of human genetic variation in different regions.
    ::14. 列出四种自然选择压力,这些压力因地域而异,并促使不同区域的人类基因变异演变。

    15. You may have noticed that when a sudden hot day occurs during a cool period, it can feel even more uncomfortable than higher temperatures during a hot period — even with the same humidity levels. Using what you learned in this chapter, explain why you think that happens.
    ::15. 你可能已经注意到,当突然的热日发生在一个寒冷时期时,它会比热时期的气温升高感到更不舒服,即使湿度相同,利用本章中学到的东西,解释你为什么认为会发生这种情况。

    16. Increasing the basal metabolic rate ____________ body heat.
    ::16. 增加巴萨尔代谢率

    a. dissipates
    ::a. 散散

    b. reduces
    ::b. 减少

    c. increases
    ::c. 增加数

    d. evaporates
    ::d. 蒸发

    17. Which of the following is a human adaptation to high altitude?
    ::17. 以下哪些是人类适应高海拔的适应?

    a. expansion of blood vessels
    ::a. 扩大血管

    b. increase in the volume of red blood cells
    ::b. 红细胞数量增加

    c. greater concentration of hemoglobin
    ::c. 血红蛋白浓度增加

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

    18. Out of all mammals, why are humans the only ones that evolved lactase persistence?
    ::18. 在所有哺乳动物中,为什么人类是唯一进化乳腺持久性的人?

    19. If the Inuit people who live in the Arctic were not able to get enough vitamin D from their diet, what do you think might happen to their skin color over a long period of time? Explain your answer.
    ::19. 如果生活在北极的因努伊特人无法从他们的饮食中获得足够的维生素D,那么你认为他们的肤色在很长一段时间内会发生什么后果?解释你的答复。

    20. Explain why malaria has been such a strong force of natural selection on human populations.
    ::20. 解释为什么疟疾是人类自然选择的强大力量。

    21. Give one example of “heterozygote advantage” (i.e. when the heterozygous genotype has higher relative fitness than the dominant or recessive homozygous genotype) in humans.
    ::21. 举一例说明人类的 " 异体兹古特优势 " (即异体兹古斯基因型比主要或封闭性同质古斯基因型更适合)。

    22. What is one way in which humans have evolved genetic adaptations in response to their food sources?
    ::22. 人类根据自己的食物来源而改变基因适应的方式之一是什么?

    23. What kind of response to environmental stresses can occur in adults?
    ::23. 成人对环境压力可以作出何种反应?

    a. acclimatization
    ::a. 升级化

    b. cultural response
    ::b. 文化反应

    c. developmental adjustment
    ::c. 发展调整

    d. A and B
    ::d. A和B

    24. Do you think adaptation to high altitude evolved once or several times? Explain your reasoning.
    ::24. 你认为对高海拔的适应是否演变了一次或几次?解释一下你的推理。

    25. A dangerous increase in the body’s core temperature is also known as...
    ::25. 人体核心温度的危险上升也被称为:

    a. hyperthermia
    ::a. 高温

    b. hypothermia
    ::b. 低温

    c. hypoxia
    ::c. 缺氧

    d. heat acclimatization
    ::d. 热通热

    26. Which of the following are diseases caused by parasites?
    ::26. 以下哪些是寄生虫引起的疾病?

    a. toxoplasmosis
    ::a. 透析病

    b. hemolytic disease of the newborn
    ::b. 新生儿血液性疾病

    c. malaria
    ::c. 疟疾

    d. A and C
    ::d. A和C

    e. all of the above
    ::e. 以上所有内容