澳洲南美洲有袋类动物家族树归类研究取得进展
文章来源:未知 文章作者:meng 发布时间:2010-07-28 02:27 字体: [ ]  进入论坛
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Debates have raged for decades about how to arrange the Australian and South American branches of the marsupial1(有袋类动物) family tree. While marsupials like the Australian tammar wallaby(塔马尔沙袋鼠) and the South American opossum(负鼠) seem to be quite different, research by Maria Nilsson and colleagues at the University of Münster, soon to be published in the online open access journal PLoS Biology, shows otherwise. Using sequences of a kind of "jumping gene," the team has reconstructed the marsupial family to reveal that all living Australian marsupials have one ancient origin in South America. This required a simple migration2 scenario3 whereby theoretically only one group of ancestral South American marsupials migrated across Antarctica to Australia. Previous studies theorize that marsupials originated in Australia and that some lineages(血统,家系) might have been split when the landmasses separated 80 million years ago. There are few ancient marsupial fossils found in South America or Australia, and previous genetic4 studies based on nuclear and mitochondrial(线粒体的) genes5 have revealed contradictory6 results about which lineages are most closely related and which split off first.

Nilsson, Jürgen Schmitz, and colleagues screened the genomes of the South American opossum and the Australian tammar wallaby, as well as the DNA7 of 20 other marsupial species, including the wallaroo(大袋鼠) , the common wombat8(袋熊) , and the marsupial mole9 for retroposons(逆转录子) . Retroposons are unlikely to independently arise in both these species in exactly the same part of the genome by chance and can be used as unambiguous(清楚的,明白的) phylogenetic markers. Thus, the overwhelming likelihood is that retroposons shared between species are derived10 from a long-lost ancestor.

Today's Australian marsupials appear to have branched off from a South American ancestor to form all currently known marsupials—kangaroos, the rodent-like bandicoots(袋狸) , and the Tasmanian devil. It is still a mystery how the two distinct Australian and South American branches of marsupials separated so cleanly, but perhaps future studies can shed light on how this occurred.



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1 marsupial 47zzn     
adj.有袋的,袋状的
参考例句:
  • Koala is an arboreal Australian marsupial.考拉是一种澳大利亚树栖有袋动物。
  • The marsupial has been in decline for decades due to urban sprawl from car accidentsdog attacks.这种有袋动物其数量在过去几十年间逐渐减少,主要原因是城市的扩张、车祸和狗的袭击。
2 migration mDpxj     
n.迁移,移居,(鸟类等的)迁徙
参考例句:
  • Swallows begin their migration south in autumn.燕子在秋季开始向南方迁移。
  • He described the vernal migration of birds in detail.他详细地描述了鸟的春季移居。
3 scenario lZoxm     
n.剧本,脚本;概要
参考例句:
  • But the birth scenario is not completely accurate.然而分娩脚本并非完全准确的。
  • This is a totally different scenario.这是完全不同的剧本。
4 genetic PgIxp     
adj.遗传的,遗传学的
参考例句:
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
5 genes 01914f8eac35d7e14afa065217edd8c0     
n.基因( gene的名词复数 )
参考例句:
  • You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因,所以能够活得很长。 来自《简明英汉词典》
  • Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪
6 contradictory VpazV     
adj.反驳的,反对的,抗辩的;n.正反对,矛盾对立
参考例句:
  • The argument is internally contradictory.论据本身自相矛盾。
  • What he said was self-contradictory.他讲话前后不符。
7 DNA 4u3z1l     
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句:
  • DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
  • Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。
8 wombat RMvzA     
n.袋熊
参考例句:
  • Wombat wanted to wiggle along the ground.袋熊想在地面上扭动前进。
  • A wombat stops in front a ranger's vehicle.袋熊停在护林员的车辆前面。
9 mole 26Nzn     
n.胎块;痣;克分子
参考例句:
  • She had a tiny mole on her cheek.她的面颊上有一颗小黑痣。
  • The young girl felt very self- conscious about the large mole on her chin.那位年轻姑娘对自己下巴上的一颗大痣感到很不自在。
10 derived 6cddb7353e699051a384686b6b3ff1e2     
vi.起源;由来;衍生;导出v.得到( derive的过去式和过去分词 );(从…中)得到获得;源于;(从…中)提取
参考例句:
  • Many English words are derived from Latin and Greek. 英语很多词源出于拉丁文和希腊文。 来自《简明英汉词典》
  • He derived his enthusiasm for literature from his father. 他对文学的爱好是受他父亲的影响。 来自《简明英汉词典》
TAG标签: species genome marsupials
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