分子与细胞生物学 10 - L4c DNA and Chromosomes (2)

    本期的内容是第四章-DNA与染色体的最后一节：4c Structure of Chromatin (eukaryotic cells) . 如果有不太明白的或者有错误的地方随时来找UP主喔~ 文集本部分的参考文献Essential Cell Biology, 5th ed. Alberts, et al. 2019. 部分内容来自khanacademy与维基百科.

    本期封面图：https://www.onlinebiologynotes.com/wp-content/uploads/2020/06/Chromatin-structure-composition-and-packaging.jpg

    本期内容笔记以文本+笔记图片混合的形式呈现。

Chromatin in the Chromosome, packs DNA. (Human - 3 billion base pairings) 

    Dividing cells - 10000x compaction 

    Non-dividing cells - 500x compaction

Chromatin Packing Level 1:

    Histones: Basic protein found in eukaryotic cell nuclei that pack and order DNA into structural units called nucleosomes

    Nucleosome = Octamer (8 core histones) + naked DNA

    Histones: non-specific, can bind to any DNA sequence. Histones are positively charged, abundant in lysine and arginine - interact with the negatively charged backbone.

    Every histone protein has a unstructured tail that sticks out of the nucleosome disk.

Chromatin Packing Level 2:

    DNA less accessible, more tightly packed; DNA not need to be transcribed; Nucleosomes twist into a 30-nm fiber: Need naked DNA, nucleosomes with octameric histone core, and when H1 histone that binds the linker DNA.

Higher levels: involve non-histone proteins

接下来的两页为笔记图片：

本次内容到此结束，感谢阅读！下一期将开始第五章内容：DNA复制。

作者：離久-張所長