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03 Jun 09

研究者發現垃圾 DNA 的重要角色

  • 在單細胞、池生的（pond-dwelling）生物體，Oxytricha（尖毛蟲屬）中，稱為轉位子（transposons）的基因，製造出一種細胞蛋白質，稱為轉位酶（transposases）。在生長期間，轉位酶顯然 首先影響成千上萬個 DNA 片段重組（regroup）
31 May 09

人為何生而為人？

人類和黑猩猩的基因組只有些微不同，但是科學家在其中找到了人類獨有的DNA片段，這些片段在腦、手與其他部位作用，讓人類與黑猩猩大不相同。

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biology brain DNA

  • 在600萬年前人類和黑猩猩的譜系分開後，人類基因組的30億個核酸中，僅有約1%，也就是約1500萬個核酸鹼基改變了
  • 基因組中有些改變較快的區域，是受到了正向天擇的記號，那些突變有利於生物的生存和繁衍，因此更有可能傳給後代。換句話說，在人類和黑猩猩分開後變化最多的編碼，就是最有可能塑造我們成為人類的序列
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28 Jun 07

癌症的另一種理論：染色體錯亂

  • 嚴重的毒性、有限的效力

    以及最終的抗藥性
  • 染色體理論
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27 Jun 07

研究發現晝夜節律主宰生命機能

  • 每個基

    因表現路徑都受到晝夜節律的影響，而且每組基因節律時間（timing of

    the rhythms）的同步化很重要
07 Jun 07

Chemotaxis in Bacteria

  • To the advantage of these bacteria, they are able to detect both attractant and repellant chemicals (6). When an increasing concentration of an attractant (sugar) or decreasing concentration of a repellant (fatty acid) is detected, the bacteria will decrease the frequency at which it tumbles and will thus swim for longer periods (5). This gives the bacteria more of an opportunity to swim into an area where the concentration of a needed chemical is high and away from areas which contain toxic chemicals. Conversely, detection of decreasing concentrations of attractants or increasing concentrations of repellants causes bacteria to increase their tumbling frequencies (5). While the tumbling remains random, increasing the amount of tumbling allows bacteria to change direction more often, hopefully oriented away from a repellant and toward an attractant gradient. What must be understood here is that the movement of these bacteria is still random just as it would be in a solution where there was no detection of chemical gradients; however, the bacteria modify their movement patterns by increasing and decreasing the frequency at which they change from swimming to tumbling.
  • motile bacteria move via rotation of one or more flagella, turning counter-clockwise when swimming and clockwise when tumbling

简单生物也能“记住”觅食路线 -单细胞生物|运动-生物通

  • 当一只阿米巴虫向右转弯后，下一次向左转的可能是向右转的2倍，反之亦然
  • 转弯时，阿米巴虫向预方向伸展部分“躯体”，在细胞的同侧产生了一道蛋白痕，这道痕使细胞临时性更倾向于向相反方向运动，这种机制使阿米巴虫来避免了圆周运动，“周游”的领域更广阔。
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