????本期的內(nèi)容是第四章-DNA與染色體的最后一節(jié)：4c Structure of Chromatin (eukaryotic cells) . 如果有不太明白的或者有錯誤的地方隨時來找UP主喔~ 文集本部分的參考文獻Essential Cell Biology, 5th ed. Alberts, et al. 2019. 部分內(nèi)容來自khanacademy與維基百科.

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

? ? 本期內(nèi)容筆記以文本+筆記圖片混合的形式呈現(xiàn)。

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

接下來的兩頁為筆記圖片：

本次內(nèi)容到此結(jié)束，感謝閱讀！下一期將開始第五章內(nèi)容：DNA復(fù)制。

作者：離久-張所長