Richard F, Dutrillaux B
UMR 147 CNRS, Institut Curie, Section Recherche, Paris, France.
Chromosome Res. 1998 Jun;6(4):263-8. doi: 10.1023/a:1009262622325.
Great apes (Pongidae) possess a chromosome similar to human chromosome 21 (HSA21), whose trisomy was described in both chimpanzee and orangutan. Having studied more than 200 mammalian species by chromosome banding techniques and reconstructed Primates phylogeny, we reinvestigated, using fluorescence in situ hybridization, primate and non-primate mammals that we considered to possess a karyotype representative of their taxonomic group. DNA sequences from HSA21 and human chromosome 3 (HSA3) are synthenic and form a large and similar chromosome in species from distinct orders, such as Primates, Carnivora, Artiodactyla and Scandentia. In Primates, this syntheny was maintained in lemurs and was disrupted by a fission in Old World monkeys (catarrhines). Another fission occurred in New World monkeys (platyrrhines), conserving a syntheny between HSA21 and a very short segment of HSA3 DNA sequences. Thus, the ancestral HSA21 was formed after the divergence between platyrrhines and catarrhines and before the emergence of Cercopithecidae. This exposed the human and Pongidae ancestry to trisomy 21 for a period of 30-50 million years, while, in other catarrhines, the equivalent of HSA21 was further involved in various translocations forming large chromosomes whose aneuploidy, very probably incompatible with life, protected them against trisomy 21.
大猩猩科动物拥有一条与人类21号染色体（HSA21）相似的染色体，在黑猩猩和猩猩中都曾描述过该染色体的三体现象。我们通过染色体显带技术研究了200多种哺乳动物，并重建了灵长类动物的系统发育，之后利用荧光原位杂交技术，对我们认为拥有代表其分类群核型的灵长类和非灵长类哺乳动物进行了重新研究。HSA21和人类3号染色体（HSA3）的DNA序列是同线的，并且在不同目（如灵长目、食肉目、偶蹄目和树鼩目）的物种中形成了一条大的相似染色体。在灵长类动物中，这种同线性在狐猴中得以保留，而在旧世界猴（狭鼻猴类）中因一次裂变而被破坏。在新世界猴（阔鼻猴类）中发生了另一次裂变，保留了HSA21与HSA3 DNA序列的一个非常短的片段之间的同线性。因此，祖先的HSA21是在阔鼻猴类和狭鼻猴类分化之后、猕猴科出现之前形成的。这使得人类和大猩猩科动物在3000万至5000万年的时间里存在21号染色体三体的情况，而在其他狭鼻猴类中，相当于HSA21的染色体进一步参与了各种易位，形成了大染色体，其非整倍体很可能与生命不相容，从而保护它们免受21号染色体三体的影响。
