細(xì)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(xì)胞分裂每次都是一個(gè)母細(xì)胞變成兩個(gè)子細(xì)胞。細(xì)胞先按照原有成分復(fù)制出一套完全一樣的副本，包括細(xì)胞核中的</font>DNA<font face="宋體">染色體；然后進(jìn)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(shí)它們還在同一個(gè)細(xì)胞內(nèi)；最后是胞質(zhì)分裂，一個(gè)細(xì)胞分成兩個(gè)子細(xì)胞，時(shí)間恰好在有絲分裂結(jié)束時(shí)。</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(gè)世紀(jì)前，德國(guó)生物學(xué)家西奧多</font>&middot;博韋里通過海 膽卵實(shí)驗(yàn)提出假說，錯(cuò)誤分裂會(huì)導(dǎo)致細(xì)胞染色體倍數(shù)異常和細(xì)胞不受遏制地生長(zhǎng)，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(xì)胞的細(xì)胞核中，染色體常常會(huì)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(xì)胞會(huì)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(xì)胞則含有錯(cuò)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(xì)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(xì)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(jìn)一步觀察了人類細(xì)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(gè)細(xì)胞變成兩個(gè)核開始觀察，吃驚地發(fā)現(xiàn)細(xì)胞沒經(jīng)過有絲分裂，而是直接由一個(gè)細(xì)胞變成了兩個(gè)細(xì)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(gè)新細(xì)胞都遺傳了一個(gè)完整無缺的細(xì)胞核，包含一套完整染色體。分裂發(fā)生的時(shí)間出乎預(yù)料，是在延遲生長(zhǎng)階段，而不是在有絲分裂結(jié)束時(shí)。他們還做了大量額外實(shí)驗(yàn)，以確定這種分裂和正常的細(xì)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>