如果存在時(shí)間機(jī)器,，那么把一種生物放進(jìn)去,，能不能使它逆轉(zhuǎn)退回遠(yuǎn)祖的狀態(tài)呢？
葡萄牙和美國的科研人員用果蠅作為對(duì)象研究了這個(gè)有趣的問題,，他們?cè)趯?shí)驗(yàn)室中模擬重建了果蠅遠(yuǎn)祖生活的環(huán)境,。實(shí)驗(yàn)用果蠅是1975年從野外捕捉的果蠅的后代，已經(jīng)在各種環(huán)境中經(jīng)歷了500代的進(jìn)化,，許多特性已經(jīng)隨環(huán)境變化而發(fā)生了改變,。
實(shí)驗(yàn)中，科研人員把這些果蠅放回類似其祖先曾經(jīng)生活過的環(huán)境中,，讓它們?cè)俳?jīng)歷50代的進(jìn)化,。如果果蠅出現(xiàn)逆向進(jìn)化，那么它們3號(hào)染色體上的DNA（脫氧核糖核酸）一個(gè)片斷將會(huì)有所變化,。
研究得出的結(jié)論是什么呢,？果蠅的確會(huì)“返祖”，但到一定程度就停止了。
科研人員在新一期英國《自然·遺傳學(xué)》雜志上報(bào)告說,，一旦果蠅能自如適應(yīng)新環(huán)境,，逆向進(jìn)化的時(shí)鐘就會(huì)停止，但這時(shí)果蠅的DNA與其遠(yuǎn)祖并不一定一致,。
科研人員說,，平均來說，只有一半的基因序列逆轉(zhuǎn)變回到和其祖先相同的狀態(tài),。這項(xiàng)研究也表明,，進(jìn)化比人們想像的要復(fù)雜得多，甚至有時(shí)取決于偶然事件,。
這項(xiàng)研究也從一方面表明,，物種能夠通過基因重組而非基因突變一代代地進(jìn)化。（生物谷Bioon.com）
生物谷推薦原始出處：
Nature Genetics 11 January 2009 | doi:10.1038/ng.289
Experimental evolution reveals natural selection on standing genetic variation
Henrique Teotónio1, Ivo M Chelo1, Martina Bradi2, Michael R Rose3 & Anthony D Long3
Evolution depends on genetic variation generated by mutation or recombination from standing genetic variation. In sexual organisms, little is known about the molecular population genetics of adaptation and reverse evolution1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11. We carry out 50 generations of experimental reverse evolution in populations of Drosophila melanogaster, previously differentiated by forward evolution, and follow changes in the frequency of SNPs in both arms of the third chromosome. We characterize the effects of sampling finite population sizes and natural selection at the genotype level. We demonstrate that selection has occurred at several loci and further that there is no general loss or gain of allele diversity. We also observe that despite the complete convergence to ancestral levels of adaptation, allele frequencies only show partial return.
1 Instituto Gulbenkian de Ciência, Apartado 14, P-2781-901 Oeiras, Portugal.
2 Department of Biology, New York University, New York, New York 10003, USA.
3 Department of Ecology and Evolutionary Biology, University of California, Irvine, California 92697, USA.
