,武汉大学生命科学学院,武汉 430072Teaching practice in human genetics integrated into general education
Hanhua Cheng, Rongjia Zhou,College of Life Sciences, Wuhan University, Wuhan 430072, China通讯作者: 周荣家，教授，博士生导师，研究方向：遗传学。E-mail:rjzhou@whu.edu.cn
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编委: 卢大儒
收稿日期:2019-09-19修回日期:2019-11-21网络出版日期:2019-12-06
| 基金资助: |
Received:2019-09-19Revised:2019-11-21Online:2019-12-06
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摘要
通识教育已经成为大学高等教育的重要组成部分,强调通专结合的办学理念,要求践行“以人为本”的教育实践。在教学实践中存在不少困难和困惑,需要不断总结和发展中国特色的通识教育体系。本文凝练了在人类生物学教学实践中如何融入人类遗传学知识的通识教学理念、案例和分析,以“人是什么”为切入点引入贴近生活的教学内容。通过现代进化基因组学知识,解析人类自身发展的过去、现在和未来所涉及的生物学核心问题。剖析人的经典属性及其与通识教育的特殊关联,进而引出基于问题的深层次思考。
关键词：
Abstract
General education is an important part in higher education, which emphasizes the educational idea of integration of generality with specialty, and practices people-oriented education concept. However, there are some difficulties and puzzles in general education. Now the general education system with Chinese characteristics is needed to be established through practice and development. In this paper, we enumerate how to integrate knowledge of human genetics in practice of general education, teaching cases, and relevant analysis with concepts of general education. Using questions as “what are human beings?” as a leverage, we introduce teaching contents closely related to daily life. For example, we explain the past, present and future of human beings through contemporary evolutionary genomics teaching. In addition, we introduce problem-based deep thinking for students, thus integrating classical attributes of human beings into general education.
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本文引用格式
程汉华, 周荣家. 通识教育中融入人类遗传学的教学实践. 遗传[J], 2020, 42(2): 222-229 doi:10.16288/j.yczz.19-292
Hanhua Cheng.
教育的实质应该回归以人为本,培养健全人格,全面提高人的素质,高等教育尤为如此,不仅要追求优质的专业教育,更要践行“以人为本”的通识教育。高等教育为我国现代化建设提供了人才保障,输送了大量国家所需的专业人才。我国普通本科招生规模逐渐扩大,入学率近50%,很快将跨入高等教育普及化发展阶段。高等教育工作任重道远。结合国内外教育历史与现实,我国改革开放40年的高等教育实践已经证明,通识教育与专业教育同等重要,二者相辅相成。本文将通过通识课程人类生物学的教学实践,总结和挖掘“以人为本”的教学理念和教学思路和方法,特别以人类遗传学为案例,分析人的经典属性在通识教育中的核心地位。
1 通识教育的核心理念
在通识教育的实践中,各个大学都有自己的理解和实践,也都遇到各种困惑和困难,包括理念的建立和课时的安排等,例如如何从繁多的专业课程学时中给通识课程分出学时等问题。狭义上讲,通识教育是通与专的结合,而更广义的理解应该是如何践行“以人为本”的教育理念。清华大学成立了通识教育实验区新雅学院。北京大学不仅成立了元培学院,而且在“通专”结合方面进行了各种实践。复旦大学在教与学两方面推进改革举措,建立“以人为本,以德为先”的人才培养理念。浙江大学建立了竺可桢学院,在通专结合方面开设了一批高品质的荣誉课程。武汉大学系统地发展了通识教育的核心理念,即“博雅弘毅,文明以止,成人成才,四通六识”。秉持“人文化成”之理念,以“成人”教育统领成才教育(http://gec.whu. edu.cn/tszx/zxjj.htm)。《人类生物学》作为该校最早开设的通识课程之一,始终践行上述通识教育的核心理念,坚持“以人为本”作为经典。从2008年开课以来,一直深受学生欢迎。历经“武大通识1.0”到“武大通识3.0”的建设,已经成为通识教育的重要组成部分。
2 人类生物学的教学实践
2.1 教学目标、大纲与教学方法
素质教育正成为当今大学教育的趋势。作为通识教育课程,《人类生物学》课程旨在培养大学生健全的人格,拓展与完善大学生的知识结构,造就更多有创新潜能的复合型人才。《人类生物学》是为各专业学生开设的全校性通识课程,适合于文科、理科、工科和医学等专业大学生学习人类自身知识的课程。该课程通过现代化多媒体教学手段进行展示,强调人类生物学知识的基础与前沿、科学性与趣味性、实用性与交叉性、热点问题与系统知识的有机组合,注重联系实际,贴近生活,易于了解和接受。教学中反映人类生物学与理、工和人文社科等学科的交叉渗透,反映现代生命科学发展的最新成果,以及地球与人类生存发展的密切关联。课程以“人是什么”为切入点,对人类自身的过去、现在和未来所涉及的生物学问题进行讲授。《人类生物学》教学内容选择上始终体现人文关怀,贴近生命和生活,按照人类生物学知识范围,设计若干知识模块。教学共分6章(表1)。为了便于各专业本科生选修的时间灵活性,在总学时上压缩到最小,安排一个学分,共16学时。在教学方法上,全部采用多媒体教学。教学手段主要包括自制幻灯片、自制多媒体链接、视频短片,VCD播放,以及精准个性化教学与小组交流等丰富多彩的方法。Table 1
表1
表1教学内容、教学方法和学时安排
Table 1
| 教学内容 | 教学方法与手段 | 学时 |
|---|---|---|
| 第一章 人类进化与未来 第一节 人是什么? 第二节 智人的特点及与其他动物的本质区别 第三节 智人的起源与未来 | 多媒体;VCR短片;PPT | 3 |
| 第二章 人类基因组与个人精准医学 第一节 人类基因组组成 第二节 人类基因组计划 第三节 个人精准医学 第四节 人类基因组计划的负面作用 | 多媒体;短片 PPT;讨论与互动 | 3 |
| 第三章 人类遗传与遗传性疾病 第一节 人类给下一代遗传了什么 第二节 人类遗传规律 第三节 遗传性疾病 第四节 遗传因素在遗传性疾病发生中的作用 第五节 癌症遗传 | 多媒体;PPT;色盲基因测试; 分析讨论 | 3 |
| 第四章 人类的生殖与人口性比 第一节 人类的生殖生理与健康 第二节 有性生殖是人类生存繁衍的必经途径 第三节 人类性别决定与人口性比 第四节 辅助生殖策略与潜在新技术 | 多媒体;PPT;试管婴儿 案例分析;讨论 | 3 |
| 第五章 现代生命科学技术对人类的挑战 第一节 转基因技术 第二节 人类干细胞技术 第三节 实验室设计婴儿 | 多媒体;PPT 转基因案例分析;讨论 | 3 |
| 第六章 精准个性化教学与小组交流 | 多媒体;PPT;小组交流 | 1 |
新窗口打开|下载CSV
2.2 教学效果与评估
从“武大通识1.0”到“武大通识3.0”,《人类生物学》始终贯彻落实“通识”教育理念, 满足于大学生对人类自身知识的了解和渴望。至今已开课10年,共有1470余名学生选课,每次选课平均110余人,选课学生覆盖全校文、史、理、工、农、医所有学科专业(图1)。教学评价由学院组织,百分制进行,平均得分为94.92分。不仅学生选课踊跃,而且获得了很好的教学效果。为我国培养具有通识知识背景的高级科学人才做出了贡献。图1
新窗口打开|下载原图ZIP|生成PPT图1人类生物学选课大学生学科专业分布及教学评估
A：饼图显示各学科专业的学生百分比,不同颜色显示学科专业。B：历年教学评估,百分制。红线是平均值。
Fig. 1Subject distribution of students signing up for human biology and teaching evaluation
3 以“通”为境界的人类生物学通识教学
3.1 以“通”为人格境界的总体设计
培养健全人格,以“专”为知识纵深,以“通”为人格境界。人类生物学课程的建设始终贯穿从认识“人”、了解“人”到培养“人”,以及了解自己到了解世界,以“通”为人格境界,打通文理界限。有关人类生物学学习,已经出版了不少教材和参考书,国内以陈守良和郭明德编写的《人类生物学》较为系统[1],中文翻译本有尤瓦尔·赫拉利著的《人类简史 从智人到智神》[2]。人类生物学课程教学中反映了人类生物学知识与理、工、人文社科等学科的交叉与渗透,体现了现代生命科学发展的最新成果及其产生的意义,同时关注地球与人类生存发展的密切关联。引导学生从喜欢学、主动学到无形之中塑形自我健全人格的“通”境界。3.2 人是什么?
人们对大猩猩好奇,人与大猩猩、黑猩猩以及金丝猴到底是什么关系?这就要先回答人是什么?人类生物学教学中以此问题为切入点,阐明人的属性。让学生了解自己,只有充分认识自己,才能完善人的属性,并树立健全人格。长臂猿、猩猩、大猩猩、黑猩猩与人都属于人猿超科大家族。然而,他们在不同的演化年代各自分歧独立成群,最早是长臂猿在约距今18百万年前分开独立演化,之后是猩猩在11百万年前分出,大猩猩于7~8百万年前与黑猩猩和人分开演化,最后是人类在5~7百万年前与黑猩猩分开独立演化(图2)。看来与人类更近源的是黑猩猩,而非电影中场景描述的大猩猩与人类更亲近。在教科书中没有更新关于人类的演化知识。人类生物学教学中更关注前沿热点问题,引入了新内容,使学生认识人更全面。比如,在黑猩猩与人类分开演化后不久,约4.4百万年前,人类演化的这一支出现过一类与人类更近源的猿人,即拉密达猿人。2009年美国科学家在Science杂志上发表系列报道,在埃塞俄比亚境内发现了距今已有4.4百万年的女性原始人骨骼化石[3,4,5],这是迄今发现的年代最久远的原始人骨骼化石,科学家根据出土的骨骼“复原”了其整体特征(图2)。她具有与猿类似的头部和脚趾,手掌、手腕以及骨盆格局,表明她可以用两只脚直立行走,类似人类,但脚掌的拇指分得更开,这有利于野外生存。这可能是目前已知的最早的人类祖先,即使不是,它也为研究者提供了新的参考,了解人类是怎样从大猩猩和黑猩猩等共同拥有的祖先那里演化来的。更多疑问留给学生课后思考,比如：拉密达猿人为什么没有成功演化,而在地球上消失?人类是否还在进一步演化?人类的未来如何?图2
新窗口打开|下载原图ZIP|生成PPT图2人猿超科进化树及拉密达猿人复原形态
数值显示进化分歧年代,以百万年(MYA)为单位。右下图显示拉密达猿人复原形态及脚掌化石及复原形态。
Fig. 2Phylogeny of Hominoidea and feet morphology of Ardipithecus ramidus
人的属性及与其他动物的本质区别也是学生常常提出的疑问。人类生物学课程引入如下几点思考：(1)智慧：源自人类高度发育的大脑。现代人的脑容量是近亲黑猩猩的3倍以上。增大的容量使得人类大脑具有更多的神经细胞和更复杂的神经网络。同时,介绍在人群中大脑容量也存在个体差异,以及存在智商差异等问题。(2)劳动：直立人的出现解放前肢发展为手,为劳动创造了条件。劳动在人类进化中具有决定性作用,发展劳动工具为人类演化新的一步,北京人用的石锥,非洲发现的石器组合等。劳动促进了人类进化,人类的每一代人都不是简单地重复前一代人的活动,而是在继承前一代人的劳动成果,传承现存的生产力以及与之相适应的社会关系,在继承以语言文字等形式存在的文化知识成果的基础上,进行新的创造活动,从而使人类改造自然的能力不断提高,使社会生活、社会关系不断丰富和发展,人类也由此获得了新的演化。从这个意义上讲,爱劳动是人的本能,劳动不仅为人类创造财富,更是人类演化的自然属性。(3)语言﹑文字与音乐：人类的属性首先是有了交流的语言,语言的诞生就是人类的诞生。音乐是人类的共同语言。早在3500年前的商代,中国就有了编钟,这为人类的演化提供了源泉。音乐起源于劳动,劳动赋予音乐以内容,劳动的呼声赋予音乐节奏和音调,劳动的动作给予音乐舞姿。古代与现代的诗歌、音乐和舞蹈3者是一体的,音乐-舞蹈-劳动-大脑,协调演化,因此,音乐是人类演化的产物,也促进了人类向更高级的演化。人类的语言是以命名为基础的,而动物的语言则不是。动物也可以通过有声语言进行简单的沟通和情感的表达等,但都不是以对事物的命名为基础。根据考古研究成果,人类至少在40~50万年前就开始发明出口头语言,创造出最初的词语。只有到了4~5千年前,欧亚大陆的一些民族逐步创造出比较完善的文字系统。在中国就是以表意为基础的汉字,最早是甲骨文。中国的殷墟遗址出土了距今近4千年的甲骨文,清楚地记载了甲骨文字与日历。说明中华民族的近5千年的演化历史,就是近代人类的演化史。这些关键历史的介绍,极大地激发了学生的民族自豪感和爱国热情。体现了“以人为本”统领成才教育的理念。
3.3 美洲人起源自亚洲
人们始终疑惑美洲人是从哪里来的?是什么时候迁移到美洲的?美洲人的起源与中国人有无关联?人类生物学教学始终关注这些科学问题的最新进展,让学生思考。考古学记录提示,西伯利亚人群于2.2~3万年前通过白令陆桥来到美洲,成为克罗维斯人(Clovis),即古印第安人[6]。近年来,古基因学技术的发展,为探索美洲人的起源开辟了新途径。考古研究显示,克罗维斯时代,有着丰富的劳动工具,称其为克罗维斯工具(图3A)。一般认为这些古克罗维斯人起源于亚洲,并与现代美洲人存在关联[7]。最近在美国蒙大拿州Anzick考古点找到一具婴儿(Anzick-1)骨遗物,考古分析显示,Anzick-1距今约1.2556~1.2707万年,并从中分离了古DNA。基因组测序和遗传学分析显示,Anzick-1起源于亚洲,并非来自欧洲。进一步的基因组参数分析显示,Anzick-1基因组特征与现代的美洲人相似,说明Anzick人群在后来的繁衍扩散到了整个北美洲,属于美洲原住民。后来演化为现代美洲人[8]。而且,Anzick-1基因组与中国汉人基因组聚类在一个大进化分支之内,提示其与中国汉族存在遗传关联。结合现代基因组和考古研究,说明北美洲原住民起源自亚洲(图3B)。然而,Anzick人是否来自中国古汉族人有待进一步探索,这一科学问题值得学生深思,比如,美国美洲原住民与中国古汉族人在演化历史上是否早就联系在一起?而美洲人起源于中国人?其实,北美洲原住民另外一支起源于贝加尔湖中南西伯利亚。在该地区发现的Ma-1少年化石属于这一支,约2.4万年前迁移至北美洲。Ma-1基因组测序分析显示,其Y染色体和常染色体序列与西部欧亚人相似,而不是东部亚洲[9]。这一支约占北美洲原住民祖先14%~38%。而大多数北美洲原住民起源于东部亚洲。图3
新窗口打开|下载原图ZIP|生成PPT图3美洲人起源自亚洲
A：克罗维斯人使用的劳动工具[7,8];B：北美洲原住民起源示意图,Anzick-1迁移年代约是1.26万年前跨过百令海峡,之后可能有多次从亚洲迁移到北美。北美洲原住民另外一支起源于贝加尔湖中南西伯利亚,Ma-1化石属于这一支,约2.4万年前迁移至北美洲。
Fig. 3Asian ancestry of the Clovis people in America
4 贴近生活的教学模式
人类生物学教学以通为引领,贴近生活的教学模式最能让学生热爱通识教育,从而达到塑形自我健全人格的通识教育目的。在人类基因组与个人精准医学章节的教学中,着重讨论了人类基因组计划的前因后果,以及个人基因组计划的实施对每个人生活的影响。比如,随着个人基因组测序的普及,如何保护个人基因组的隐私。在个性化给药与精准医学方面,不仅介绍最新进展,使学生了解最新学术成果,更要让学生结合自身健康,以及生病时吃药情况进行思考。目前的治病用药基本是“One-Size-Fits-All”即“一种剂量适合所有”,精准医学的发展不久将实施“Right Drug-Right Dose- Right Person”即“正确的药物-正确的剂量-正确的人”。通过体验贴近生活的教与学,学生轻松掌握了人类基因组与个人精准医学知识。同时,也提出一些问题让学生讨论,比如,随着基因组测序费用的降低,你愿意测序你的个人基因组吗?因为人基因组记录了一个生命的全部奥秘和隐私,包括疾病基因等,一方面这对于疾病的预防、诊断与治疗很有帮助;另一方面,如何保护个人及家人的基因隐私也是普遍关心的问题。在人类遗传学章节的教学中,以色盲基因的遗传为例,让每个学生都亲自参与到教与学的教学过程中,学习和了解自己的色盲基因。为了保护个人隐私,课程通过对学生一对一的教学测试,让每个学生了解自己的视力与色盲基因的遗传方式。统计显示正常视力为绝大多数,色弱也不少,还有少数色盲(图4A)。通过贴近生活的教学活动,学生普遍关心的一些问题也就迎刃而解了,比如,为什么色盲总是出现在男生,而女生没有?因为色盲基因位于X染色体,属于性连锁遗传。为什么有些人得病是绿色盲,另一些人得红色盲,因为这是两个连锁遗传基因的控制,即红视蛋白基因(red opsin)和绿视蛋白基因(green opsin)。为什么会得色盲?因为这两个基因的染色体区域DNA序列的相似性,在减数分裂时容易产生配对交换错配,导致产生突变配子所致(图4,B和C)。
图4
新窗口打开|下载原图ZIP|生成PPT图4色盲的遗传学
A：人群中色盲检查统计,显示正常、色弱和色盲3组的相对百分比;B：X染色体上红视蛋白基因与绿视蛋白基因的连锁遗传,及其减数分裂时配对交换错误导致基因重复和丢失;C：杂合子母亲中产生突变卵子,与正常男性精子受精及其后代色盲出现。
Fig. 4Genetics of color blindness
5 教学展望
通识教育已经成为高等教育的重要部分,科技社会大发展要求高等教育适应新形势,对高级人才的培养要求通专结合,强调素质教育。人类生物学是通识教育的很好模式课程,坚持“以人为本”的办学理念以及素质教育的教育实践在人类生物学教学实践中得到了体现。在教学中以“人是什么”、“精准医疗”、“红绿色盲”和“现代人起源”等一系列详细生动的案例,突出了教学内容在“人格教育”中的重要作用,并以此贯穿了贴近生活的教学方式,把人类遗传学知识巧妙地融入到通识教育的教学实践中。10年的教学改革与探索,取得了较好的效果。我国遗传学教学40年的实践探索与改革,成效显著[10,11,12,13]。我国早期****编著的经典遗传学教材(如方宗熙主编的《普通遗传学》[14]、刘祖洞主编的《遗传学》[15]以及戴灼华等主编的《遗传学》[16]等)为人类生物学中遗传学知识的教学奠定了基础。这些背景知识为人类生物学的教学提供了借鉴。近年来的遗传学教学改革实践逐步建立了我国遗传学教学体系。然而,人类生物学的教学在人类生殖、人类演化、人类伦理、人类生活与环境等方面还将继续补充和加强,争取更多的通识教学学时,逐步完善人类生物学的课程和教学体系建设,同时,在教学手段上采用线上如MOOC等手段,使其成为通识教育的典范课程。参考文献 原文顺序
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URLPMID:19810198 [本文引用: 1]
Several elements of the Ardipithecus ramidus foot are preserved, primarily in the ARA-VP-6/500 partial skeleton. The foot has a widely abducent hallux, which was not propulsive during terrestrial bipedality. However, it lacks the highly derived tarsometatarsal laxity and inversion in extant African apes that provide maximum conformity to substrates during vertical climbing. Instead, it exhibits primitive characters that maintain plantar rigidity from foot-flat through toe-off, reminiscent of some Miocene apes and Old World monkeys. Moreover, the action of the fibularis longus muscle was more like its homolog in Old World monkeys than in African apes. Phalangeal lengths were most similar to those of Gorilla. The Ardipithecus gait pattern would thus have been unique among known primates. The last common ancestor of hominids and chimpanzees was therefore a careful climber that retained adaptations to above-branch plantigrady.
DOI:10.1126/science.326_36URLPMID:19797636 [本文引用: 1]
URLPMID:19810190 [本文引用: 1]
Hominid fossils predating the emergence of Australopithecus have been sparse and fragmentary. The evolution of our lineage after the last common ancestor we shared with chimpanzees has therefore remained unclear. Ardipithecus ramidus, recovered in ecologically and temporally resolved contexts in Ethiopia's Afar Rift, now illuminates earlier hominid paleobiology and aspects of extant African ape evolution. More than 110 specimens recovered from 4.4-million-year-old sediments include a partial skeleton with much of the skull, hands, feet, limbs, and pelvis. This hominid combined arboreal palmigrade clambering and careful climbing with a form of terrestrial bipedality more primitive than that of Australopithecus. Ar. ramidus had a reduced canine/premolar complex and a little-derived cranial morphology and consumed a predominantly C3 plant-based diet (plants using the C3 photosynthetic pathway). Its ecological habitat appears to have been largely woodland-focused. Ar. ramidus lacks any characters typical of suspension, vertical climbing, or knuckle-walking. Ar. ramidus indicates that despite the genetic similarities of living humans and chimpanzees, the ancestor we last shared probably differed substantially from any extant African ape. Hominids and extant African apes have each become highly specialized through very different evolutionary pathways. This evidence also illuminates the origins of orthogrady, bipedality, ecology, diet, and social behavior in earliest Hominidae and helps to define the basal hominid adaptation, thereby accentuating the derived nature of Australopithecus.
[本文引用: 1]
DOI:10.1126/science.1153569URLPMID:18339930 [本文引用: 2]
When did humans colonize the Americas? From where did they come and what routes did they take? These questions have gripped scientists for decades, but until recently answers have proven difficult to find. Current genetic evidence implies dispersal from a single Siberian population toward the Bering Land Bridge no earlier than about 30,000 years ago (and possibly after 22,000 years ago), then migration from Beringia to the Americas sometime after 16,500 years ago. The archaeological records of Siberia and Beringia generally support these findings, as do archaeological sites in North and South America dating to as early as 15,000 years ago. If this is the time of colonization, geological data from western Canada suggest that humans dispersed along the recently deglaciated Pacific coastline.
DOI:10.1038/nature13025URLPMID:24522598 [本文引用: 2]
Clovis, with its distinctive biface, blade and osseous technologies, is the oldest widespread archaeological complex defined in North America, dating from 11,100 to 10,700 (14)C years before present (bp) (13,000 to 12,600 calendar years?bp). Nearly 50?years of archaeological research point to the Clovis complex as having developed south of the North American ice sheets from an ancestral technology. However, both the origins and the genetic legacy of the people who manufactured Clovis tools remain under debate. It is generally believed that these people ultimately derived from Asia and were directly related to contemporary Native Americans. An alternative, Solutrean, hypothesis posits that the Clovis predecessors emigrated from southwestern Europe during the Last Glacial Maximum. Here we report the genome sequence of a male infant (Anzick-1) recovered from the Anzick burial site in western Montana. The human bones date to 10,705?±?35 (14)C years?bp (approximately 12,707-12,556 calendar years?bp) and were directly associated with Clovis tools. We sequenced the genome to an average depth of 14.4×?and show that the gene flow from the Siberian Upper Palaeolithic Mal'ta population into Native American ancestors is also shared by the Anzick-1 individual and thus happened before 12,600 years?bp. We also show that the Anzick-1 individual is more closely related to all indigenous American populations than to any other group. Our data are compatible with the hypothesis that Anzick-1 belonged to a population directly ancestral to many contemporary Native Americans. Finally, we find evidence of a deep divergence in Native American populations that predates the Anzick-1 individual.
DOI:10.1038/nature12736URL [本文引用: 1]
The origins of the First Americans remain contentious. Although Native Americans seem to be genetically most closely related to east Asians(1-3), there is no consensus with regard to which specific Old World populations they are closest to(4-8). Here we sequence the draft genome of an approximately 24,000-year-old individual (MA-1), from Mal'ta in south-central Siberia(9), to an average depth of 1x. To our knowledge this is the oldest anatomically modern human genome reported to date. The MA-1 mitochondrial genome belongs to haplogroup U, which has also been found at high frequency among Upper Palaeolithic and Mesolithic European hunter-gatherers(10-12), and the Y chromosome of MA-1 is basal to modern-day western Eurasians and near the root of most Native American lineages(5). Similarly, we find autosomal evidence that MA-1 is basal to modern-day western Eurasians and genetically closely related to modern-day Native Americans, with no close affinity to east Asians. This suggests that populations related to contemporary western Eurasians had a more north-easterly distribution 24,000 years ago than commonly thought. Furthermore, we estimate that 14 to 38% of Native American ancestry may originate through gene flow from this ancient population. This is likely to have occurred after the divergence of Native American ancestors from east Asian ancestors, but before the diversification of Native American populations in the New World. Gene flow from the MA-1 lineage into Native American ancestors could explain why several crania from the First Americans have been reported as bearing morphological characteristics that do not resemble those of east Asians(2,13). Sequencing of another south-central Siberian, Afontova Gora-2 dating to approximately 17,000 years ago(14), revealed similar autosomal genetic signatures as MA-1, suggesting that the region was continuously occupied by humans throughout the Last Glacial Maximum. Our findings reveal that western Eurasian genetic signatures in modern-day Native Americans derive not only from post-Columbian admixture, as commonly thought, but also from a mixed ancestry of the First Americans.
URLPMID:369473 [本文引用: 1]
End-stage kidneys in patients who are receiving long-term intermittent treatment with hemodialysis are metabolic structures that participate in many body processes and that themselves develop and change despite severe excretory deficiencies. Nephron loss is severe. Other lesions in such kidneys include the following: smooth muscle nodules that arise in necrotic arteries and arterioles; embryonal hyperplasia of Bowman's capsular epithelium; remodeling of the arteries and veins; tubular atrophy; dilation and cyst formation (acquired cystic disease); arteriolar granular cell hyperplasia and hypertension; deposits of oxalate, calcium, and immune complexes; interstitial fibrosis with collagen and smooth muscle; mucoid change; and cellular infiltration. This list does not include all pathologic conditions found in the end-stage--dialysis kidney. The necessity of and the criteria for an experimental model of human long-term intermittent hemodialysis for end-stage renal disease, presently lacking, are indicated.
URLPMID:369473 [本文引用: 1]
End-stage kidneys in patients who are receiving long-term intermittent treatment with hemodialysis are metabolic structures that participate in many body processes and that themselves develop and change despite severe excretory deficiencies. Nephron loss is severe. Other lesions in such kidneys include the following: smooth muscle nodules that arise in necrotic arteries and arterioles; embryonal hyperplasia of Bowman's capsular epithelium; remodeling of the arteries and veins; tubular atrophy; dilation and cyst formation (acquired cystic disease); arteriolar granular cell hyperplasia and hypertension; deposits of oxalate, calcium, and immune complexes; interstitial fibrosis with collagen and smooth muscle; mucoid change; and cellular infiltration. This list does not include all pathologic conditions found in the end-stage--dialysis kidney. The necessity of and the criteria for an experimental model of human long-term intermittent hemodialysis for end-stage renal disease, presently lacking, are indicated.
[本文引用: 1]
[本文引用: 1]
DOI:10.16288/j.yczz.16-192URLPMID:27867153 [本文引用: 1]
The classroom is the main venue for undergraduate teaching. It is worth pondering how to cultivate undergraduate's research ability in classroom teaching. Here we introduce the practices and experiences in teaching reform in genetics for training the research quality of undergraduate students from six aspects: (1) constructing the framework for curriculum framework systematicaly, (2) using the teaching content to reflect research progress, (3) explaining knowledge points with research activities, (4) explaining the scientific principles and experiments with PPT animation, (5) improving English reading ability through bilingual teaching, and (6) testing students' analysing ability through examination. These reforms stimulate undergraduate students' enthusiasm for learning, cultivate their ability to find, analyze and solve scientific problems, and improve their English reading and literature reviewing capacity, which lay a foundation for them to enter the field of scientific research.
DOI:10.16288/j.yczz.16-192URLPMID:27867153 [本文引用: 1]
The classroom is the main venue for undergraduate teaching. It is worth pondering how to cultivate undergraduate's research ability in classroom teaching. Here we introduce the practices and experiences in teaching reform in genetics for training the research quality of undergraduate students from six aspects: (1) constructing the framework for curriculum framework systematicaly, (2) using the teaching content to reflect research progress, (3) explaining knowledge points with research activities, (4) explaining the scientific principles and experiments with PPT animation, (5) improving English reading ability through bilingual teaching, and (6) testing students' analysing ability through examination. These reforms stimulate undergraduate students' enthusiasm for learning, cultivate their ability to find, analyze and solve scientific problems, and improve their English reading and literature reviewing capacity, which lay a foundation for them to enter the field of scientific research.
URLPMID:1106780 [本文引用: 1]
The kinetics of the inactivation of yeast inorganic pyrophosphatase by sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide were studied. Micellar forms of detergents were shown to be an active reagetns under conditions tudied. The possible scheme of the inactivation including reversible formation of the micellar-protein complex and subsequent penetration of the bound detergent molecules in the protein is proposed. The enzyme ionogenic group with pK 7-8 by 25 degrees C is found to be responsible for conformational changes of the enzymes. The influence of the specific ligands on inactivation of yeast pyrophosphatase by SDS is studied, and dissociations constants of corresponding enzyme-ligand complexes are calculated.
URLPMID:1106780 [本文引用: 1]
The kinetics of the inactivation of yeast inorganic pyrophosphatase by sodium dodecyl sulfate (SDS) and cetyltrimethyl ammonium bromide were studied. Micellar forms of detergents were shown to be an active reagetns under conditions tudied. The possible scheme of the inactivation including reversible formation of the micellar-protein complex and subsequent penetration of the bound detergent molecules in the protein is proposed. The enzyme ionogenic group with pK 7-8 by 25 degrees C is found to be responsible for conformational changes of the enzymes. The influence of the specific ligands on inactivation of yeast pyrophosphatase by SDS is studied, and dissociations constants of corresponding enzyme-ligand complexes are calculated.
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