細胞分裂新形式

<p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><font face="宋體">正常細胞分裂每次都是一個母細胞變成兩個子細胞。細胞先按照原有成分復(fù)制出一套完全一樣的副本，包括細胞核中的</font>DNA<font face="宋體">染色體；然后進入有絲分裂階段，將這兩套完全一樣的成分朝相反方向分開，此時它們還在同一個細胞內(nèi)；最后是胞質(zhì)分裂，一個細胞分成兩個子細胞，時間恰好在有絲分裂結(jié)束時。</font></span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p> <p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><font face="宋體">一個世紀前，德國生物學(xué)家西奧多</font>&middot;博韋里通過海 膽卵實驗提出假說，錯誤分裂會導(dǎo)致細胞染色體倍數(shù)異常和細胞不受遏制地生長，這就是癌癥。在</span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p> <p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><font face="宋體">癌細胞的細胞核中，染色體常常會在分裂過程中形成不止兩套而是多套，約</font>14%<font face="宋體">的乳腺癌和</font><font face="Calibri">35%</font><font face="宋體">的胰腺癌細胞會有</font><font face="Calibri">3</font><font face="宋體">套或更多染色體，沒有多余染色體的癌細胞則含有錯誤染色體。</font></span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p> <p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;">研究小組給人類細胞復(fù)制出了多倍染色體，以模擬癌癥。他們用一種常規(guī)化學(xué)物質(zhì)阻止了胞質(zhì)分裂，結(jié)果發(fā)現(xiàn)分裂并未顯出異常，子細胞在大部分情況下看起來都很正常，這和博韋里假設(shè)相悖。</span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p> <p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><font face="宋體">他們進一步觀察了人類細胞是怎樣恢復(fù)正常染色體倍數(shù)的。該校醫(yī)學(xué)與公共衛(wèi)生學(xué)院醫(yī)學(xué)部血液</font>&mdash;腫瘤學(xué)副教授、主管研究員馬克&middot;博卡德說：&ldquo;我們從一個細胞變成兩個核開始觀察，吃驚地發(fā)現(xiàn)細胞沒經(jīng)過有絲分裂，而是直接由一個細胞變成了兩個細胞。&rdquo;</span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p> <p class="MsoNormal"><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><font face="宋體">每個新細胞都遺傳了一個完整無缺的細胞核，包含一套完整染色體。分裂發(fā)生的時間出乎預(yù)料，是在延遲生長階段，而不是在有絲分裂結(jié)束時。他們還做了大量額外實驗，以確定這種分裂和正常的細胞分裂形式</font>&ldquo;胞質(zhì)分裂&rdquo;不同。</span><span style="mso-spacerun:'yes';font-family:宋體;mso-ascii-font-family:Calibri;mso-hansi-font-family:Calibri;mso-bidi-font-family:'Times New Roman';font-size:9.0000pt;mso-font-kerning:1.0000pt;"><o:p></o:p></span></p>