What are 'model organisms'?
28/8/02 By Richard Twyman
A model organism is a species that has been widely studied, usually becau it is easy to maintain and breed in a laboratory tting and has particular experimental advantages.
Over the years, a great deal of data has accumulated about such organisms and this in itlf makes them more attractive to study. Model organisms are ud to obtain information about other species – including humans – that are more difficult to study directly.
We can distinguish three major types of model organism:
Genetic model organisms
The are species that are amenable to genetic analysis, i.e. they breed in large numbers and have a short generation time so large-scale cross can be t up and followed over s
everal generations. Many different mutants are generally available and highly detailed genetic maps can be created. Examples include baker's yeast (Saccharomyces cerevisiae), the fruit fly (Drosophila melanogaster) and the nematode worm (Caenorhabditis elegans).
Experimental model organisms
The species may not necessarily be genetically amenable (i.e. they may have long generation intervals and poor genetic maps) but they have other experimental advantages. For example, the chicken and the African clawed frog Xenopus laevis have many disadvantages in terms of genetics but they produce robust embryos that can be studied and manipulated with ea. The species are widely ud model organisms in developmental biology.
Genomic model organisms
Regardless of their genetic or experimental advantages and disadvantages, certain speci
es are chon as model organisms becau they occupy a pivotal position in the evolutionary tree or becau some quality of their genome makes them ideal to study.
An example is the puffer fish (Fugu rubripes) which has a similar gene repertoire to humans but a much smaller genome (400 million ba pairs instead of 3000 million). The difference in size is mainly due to the prence of more repetitive DNA, larger gments of DNA between genes and larger introns in the human genome.
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Another consideration that must be addresd is the relevance of model organisms to humans. Surprisingly, over 60 per cent of the human dia genes that have been identified thus far have counterparts in the fly and worm, revealing a core of about 1500 gene families that is conrved in all animals.
Genes affecting more evolutionarily advanced features, such as our immune system, are less likely to have direct counterparts in simple animals. For the systems, we require clor models such as the mou . A great deal has been learned about humans by mapping and isolating mou genes and using the as a short cut to find corresponding
human genes. The mou genome is similarly organid to the human genome and large blocks of genes are even arranged in the same order (e Comparative genomics ). Mice have been extensively ud to establish dia models by mimicking the gene defects en in humans, and the models can be ud to test the efficacy of new drugs.
小家鼠
小家鼠（学名Mus musculus）也称为家鼠、小鼠或老鼠。世界各地也有小家鼠。是生物学上的模式生物之一，它们和人类的构造是很相似的，而且鼠繁殖得很快，价钱也便宜。它们也是很受欢迎的宠物。不过，家鼠也是一种害兽，它们会吃掉农作物和传播疾病。人类饲养的鼠可以活两年，但在野外的鼠通常只会活三个月。鼠通常吃素，但是它们其实是杂食的。
无危 (IUCN 2.3)
科学分类 |
界： | 动物界 Animalia | 门： | 脊索动物门 Chordata | 纲： | 哺乳纲 Mammalia | 目： | 啮齿目 Rodentia | 科： | 鼠科 Muridae | 属： | 鼠属 Mus | 种： | 小家鼠 M. musculus | | |
|
二名法 |
Mus musculus
Linnaeus, 1758 |
|
小巢状曲菌
维基百科，自由的百科全书
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小巢状曲菌
Aspergillus nidulans |
接种于真菌培养基的小巢状曲菌 |
科学分类 |
界： | 真菌界 Fungi | 环评师 亚界： | 双核亚界 Dikarya | 门： | 子囊菌门 Ascomycota | 亚门： | 盘菌亚门 Pezizomycotina | 纲： | 散囊菌纲 Eurotiomycetes | 亚纲： | 散囊菌亚纲 Eurotiomycetidae | 目： | 散囊菌目 Eurotialesac green | 科： | 发菌科 Trichocomaceae | 属： | 曲菌属 Aspergillus | 种：留学预科班 | 小巢状曲菌 A. nidulans | | |
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二名法 |
Aspergillus nidulans
(Eidam) G Winter, 1884 |
异名 do第三人称单数 |
Emericella nidulans |
|
小巢状曲菌（学名：Aspergillus nidulans），又称为构巢曲霉、构巢曲霉或钩巢曲霉等名称，有一异名hold it against me构巢裸胞壳（Emericella nidulans），是属于子囊菌门的一种丝状真菌。它已经成为真核生物细胞生物学[1]上一个重要研究生物对象超过50多年[2]，它被研究的学术主题领域相当地广，这些主题包括了遗传重组、去氧核糖核酸修复、突变、细胞周期控制、致病原理（pathogenesis）与代谢等等[3]。小巢状曲菌在它所属的曲菌属（Aspergillus）之中是少数可以经由在实验室中菌株交互减数分裂来形成有性孢子的其中一种物种。小巢状曲菌是一种雌雄同体（homothallic）真菌，这是指小巢状曲菌可以自花授粉（lf-fertilize），并且在没有其他交配个体的情形下形成子实体（sporocarp，或称孢子果，fruiting body）。
[编辑] 基因体
小巢状曲菌的基因体，是由美国麻省理工学院和哈佛大学合设的布洛德研究所（Broad Institute）定序完成，并于2005年12月发表[4]。小巢状曲菌基因体大小总共约有3000万个碱基对，并且据判断在总共8个染色体上总共大约包括了9,500个用来编码蛋白质的基因。
最近的研究从小巢状曲菌样本中成功分离出类似半胱天冬酶（caspa）的蛋白酶，这样的蛋白酶会在细胞凋亡时会发生作用[5]。这些发现都在真核细胞中的线粒体introduction用法演化完整性的测定上扮演了重要的角色，这个角色就像是古老的变形菌引起细胞死亡的能力。
[编辑] 参考文献
1. ^ Osmani SA, Mirabito PM. The early impact of genetics on our understanding of cell cycle regulation in Aspergillus nidulans. Fungal Genet Biol. 2004, 41 (4): 401–10. doi:10.1016/j.fgb.2003.11.009. PMID 14998523.
2. ^ Martinelli, S. D.; J. R. Kinghorn. rpm是什么意思Aspergillus: 50 years on. Elvier. 1994. ISBN 0-444-81762-X.
bearish
3. ^ Nierman WC, May G, Kim HS, Anderson MJ, Chen D, Denning DW. What the Aspergillus genomes have told us. Med Mycol. 2005, 43 Suppl 1: S3–5. doi:10.1080/136********029049. PMID 16110785.
4. ^ Galagan JE et al. Sequencing of Aspergillus nidulans and comparative analysis with
A. fumigatus and A. oryzae. Nature. 2005, 438 (7071): 1105–15. doi:男人美白的方法10.1038/nature04341. PMID 16372000.
