Developmental Biology 抗体分子的结构 heavy chain light chain antigen-binding sites Fig 9.7 Schematic drawing of an antibody molecule. the molecule is made up of two light and two heavy chains. Most of the molecule has a constant structure but the antigen-binding sites are located in the variable region After Janeway, C A, et al.: 1997. 凵 constant region口 arable region
Developmental Biology 抗体分子的结构
Developmental Biology 抗体变异的分子基础 Germine DNA 二二m Somate recognation WJ-joined rearranged DNA Primary transcript RNA vJ c Light-chain mRN Translato Light chain protein ig 9.8 DNA rearrangements generate a functional s transcribed into RNA, together with the constant (C)region immunoglobulin light-chain gene. At the immunoglobulin sequence RNA splcing removes the RNA between the end of light chain locus, germ line DNA carnes a set of V gene the J segment and the begnning of the C region to give a segments and a set of J gene segments During B lymphocyte light-chain mRNA which is then translated into protein. In the development. one v gene segment and one J gene segment antibody molecule(illustrated bottom night). the V J, and C are joined at random by somatic recombination to give a DNA regons of the light-chain protein are indicated in red. yello sequence coding for a unique light chan variable region. This and blue, respectively. After Janeway, C.A. et al: 1997
Developmental Biology 抗体变异的分子基础
Developmental Biology 四、基因活性状的錐持和传递决定 于调控蛋白和DNA的修饰 在发育的不同阶段,不同的基因处于不同的活性 状态。 一个转录因子可以调控其它许多基因的活性,但 其作用取决于多个因素 靶基因是否含有其调控区; 其本身是否处于活化状态(eg,是否磷酸化); 其本身是否结合了其它调控因子。 调控区是否结合了其它的调控因子
Developmental Biology 在发育的不同阶段，不同的基因处于不同的活性 状态。 一个转录因子可以调控其它许多基因的活性，但 其作用取决于多个因素： 靶基因是否含有其调控区； 其本身是否处于活化状态(e.g., 是否磷酸化)； 其本身是否结合了其它调控因子。 调控区是否结合了其它的调控因子 四、基因活性状态的维持和传递决定 于调控蛋白和DNA的修饰
Developmental Biology 维持细胞基因活性状态依赖调控因子的连续存在 Protein product of gene A enters nucleus and binds control region for gene A ina positive feedback Fig 9.10 Continued expression of gene oop. Protein A also represses gene B and activates gene C regulatory proteins could maintain a pattern of differentiated gene activity T on factor A is pr gene C M uced by gene A, and acts as a positive gene regulatory protein for its own control egion. Once activated therefore, gene A remains switched on and the cell always contains A. Bottom panel: transcription factor A also acts on the control regions of genes B and C to repress and activate Transcription of gene A, Following cell division none Protein a enters the nucleus them respectvely setting up a cel-spocic repression of gene B and activation of gene c of the genes are active and the original pattem of pattern of gene expression. After cell ne activity is e division, the cytoplasm of both daughter cells contains sufficient amounts of protein A to reactivate gene A and thus maintain the pattern of expression of genes B and c
Developmental Biology 维持细胞基因活性状态依赖调控因子的连续存在
Developmental Biology 基因活性状态与染色质的结构有关 Cell in early embryo P滤eaX Maternal X 哺乳动物失活的X染色 Inactivation and 体在生殖细胞形成时才 condensation of a randomly selected x chromosome 重新恢复活性状态。 Fig 9.11 Inheritance of an inactivated Direct inheritance of the pattern X chromosome. In early mammalian of chromosome condensation embryos one of the two x chromosomes. either the patemal x (Xp) or the maternal X(Xm), is randomly inactivated In the figure, Xp is inactivated and this inactivation is maintained through many cell divisions. The inactivated chromo- some becomes highly condensed Direct inheritance of the pattern After Alberts. B et al. 1989 of chromosome condensation Only X active
Developmental Biology 基因活性状态与染色质的结构有关 哺乳动物失活的X染色 体在生殖细胞形成时才 重新恢复活性状态