Four core domains:
Two transmembrane (T) domains: forming the passageway through which the transported molecules cross the membrane
Two cytosolic ATP-binding (A) domain
在哺乳动物中ABC family蛋白转运的物质有：phospholipids，small lipophilic drugs，cholesterol
13请简述通过Transmembrane transport转运到ER膜上的蛋白质中的Stop-Transfer Anchor Sequence以及Signal-Anchor Sequence的作用
Stop-Transfer Anchor Sequence: this sequence has dual function, one is to stop the passage of polypeptide chain through the translocon, another is to become a hydrophobic transmembrane segment in the membrane bilayer.
Signal-Anchor Sequence: functions both as ER signal sequence and membrane-anchor sequence.
14 请简述三种coated vesicles的包被蛋白及其转运方向
The three different types of coated vesicles.
1） COPII: ER to cis-Golgi
2） COPI: cis-Golgi to ER; later to earlier cis-Golgi
3） Clathrin: trans-Golgi to endosome; PM to endosome; Golgi to lysosome
15。You are a graduate student tasked with writing a research proposal on germ cell
development.You learned in a stem cell biology class that primordial germ cells(PGCs) can either be specified by inheritance of asymmetrically-localized cytoplasmic factors, or by receiving an external signal from neighboring cells. You remember that mouse PGCs are specified from epiblast cells, supposedly by an external BMP4 signal received from extra-embryonic tissue You read that BMP4 knockout mouse embryos don?t form PGCs but you aren?t sure if that is enough data to differentiate between the two mechanisms described above. A helpful classmate points you to the figure below. The figure legend indicates that the pictured cells were taken from mouse embryo epiblasts of the indicated genotype. They have been in culture for a few days; half were treated with exogenous BMP4.
Q：Do these data support the specification of mouse PGCs via an external BMP4 signal rather than a cell-intrinsic mechanism? Explain why or why not, including specific mention of BMP4 necessity and sufficiency？
A：This data supports specification of mouse PGCs via an external BMP4 signal. Using blimp1staining as a readout for initial germline specification, the experiment shows (1) that cell-intrinsic BMP4 is not necessary for germline formation and(2) exogenous BMP4 is both
necessary ands ufficient, in this context, for germline specification.
(b)The experiment in figure, along with your interest in future clinical relevance, have convinced you to write your proposal on in vitro production of male germline stem cells from mouse ESCs. You will direct their differentiation with exogenous BMP4. Since directed ESC differentiation rarely produces a pure population of cells, how will you monitor your cultures for the appearance of germline cells while keeping the cells alive? (hint:what is a less invasive method of tracking the germline markers in the figure)
A: Since blimp1 is expressed early in germline development, I would put the expression of a genetic label(GFPetc) under the regulatory control of blimp1. I would monitor my cultures by microscopy and/or FACS. (Alternate methods: antibiotic resistance rather than visible label--apply drug selection to differentiating cells; homologous recombination to create blimp-driven Cre-ER and permanent label expression from ubiquitous locus upon Cre expression).
15、说明细胞骨架在细胞分裂中的作用。 微丝：胞质分裂环。有丝分裂末期，两个即将分裂的子细胞之间产生一个收缩环。研究表明，收缩环是由大量平行排列的微丝组成，由分裂末期胞质中的肌动蛋白装配而成。随着收缩环的收缩，两子细胞被分开。胞质分裂后，收缩环即消失。收缩环是非肌肉细胞中具有收缩功能的微丝束的典型代表，在很短的时间内，微丝能迅速装配以完成细胞功能，其收缩机制也是肌动蛋白和肌球蛋白的相对滑动。
微管：纺锤体和染色体运动。当细胞进入分裂期时，间期细胞质微管网架崩解，微管解聚成微管蛋白，经重新装配形成纺锤体，介导染色体的运动；分裂末期，纺锤体微管解聚为微管蛋白，经重装配形成胞质微管网。微管纺锤体可分类如下：①动粒微管：连接动粒与两极的微管；②极微管：从两极发出，在纺锤体中部互相交错重叠的微管；③星体微管：组成星体的微管。有关染色体运动的分子机制曾有两种学说：①动力平衡学说：认为染色体的运动与微管的装配-去装配有关；②滑行学说：认为染色体的运动与微管间的相互滑动有关。
16、说明微管的分子组成、装配特点及其主要功能。
分子组成：α-微管蛋白和β-微管蛋白二者形成微管蛋白异二聚体，是微管装配的基本单位。微管二聚体上有GTP结合部位。 装配特点：微管装配是一个动态不稳定过程
装配过程：①首先α-微管蛋白和β微管蛋白形成长度为8nm的二聚体；②二聚体头尾相连再形成环形或螺旋形的多聚物；③环形或螺旋形的多聚物展开成原纤维(protofilament) ，原纤维并列成片，最终形成13根原纤维；④片状物合拢成一个圆柱体，形成微管的一段；⑤二聚体不断附着到已形成的微管上，使微管进一步延长。⑤装配一般从微观组织中心开始，并且确定极性，此过程需要水解GTP。
主要功能：◆维持细胞形态
◆细胞内物质的运输 ◆细胞器的定位
◆鞭毛(flagella)运动和纤毛(cilia)运动 ◆纺锤体与染色体运动 形成基粒和中心体
17、什么是细胞周期，细胞周期各时期的主要变化是什么。
细胞从一次有丝分裂结束到下一次有丝分裂完成所经历的一个有序过程。其间细胞遗传物质和其他内含物分配给子细胞。
G1：与DNA合成启动相关，开始合成细胞生长所需要的多种蛋白质、RNA、碳水化合物、脂类等，同时染色质去凝集。G1晚期有一特定时期，完成G1/S转换。酵母称为起始点（start）。真核细胞称为限制点（R点）或检验点（checkpoint）。通过该点，细胞进入S期合成DNA
S 期：DNA合成期DNA进行半保留复制，合成新的组蛋白。新合成的DNA立即与组蛋白共同组成核小体串珠结构。DNA复制与组蛋白合成同步。 G2：DNA复制完成，DNA含量增加1倍，由G1 期的2n变成了4n。在G2期合成一定数量的蛋白质和RNA分子细胞能否进入M期要受到G2/M期检验点的检查。如细胞是否已生长到合适大小，环境因素是否有利于细胞分裂等。 M：M期即细胞分裂期，真核细胞的细胞分裂主要包括两种方式，即有丝分裂和减数分裂。遗传物质和细胞内其他物质分配给子细胞。
18、细胞周期中有哪些检验点，各起什么作用。
G1：检验点， 酵母菌称起始点，动物细胞叫限制点。作用：检查细胞体积、营养物质、生长因子、DNA损伤。 S期检验点：DNA
G2：细胞大小，DNA复制情况。
纺锤体装配检验点：染色体附着情况(所有染色体是否都与纺锤丝相连并排列在赤道版上)。装配完全才才能激活APC，促进中期向后期转化。检测MPF是否失活。
19、举例说明CDK激酶在细胞周期中是如何执行调节功能的？ 不同的CDK激酶与不同的周期蛋白结合在不同的细胞周期执行功能。 CDK1激酶和周期蛋白B结合形成MPF，在G2/M 转化过程中起调节作用： 1）CDK1激酶的激活：
周期蛋白B积累到一定量时，与CDK结合成无活性的的复合体。 Week/Mik1 和 CAK激酶催化CDK的Thr14、 Tyr15、Thr161 磷酸化。 Cdc25c 催化Thr14、 Tyr15 去磷酸化，使复合物活化。
2）MPF功能：使组蛋白磷酸化，促进染色体凝集；使核纤层蛋白磷酸化，促使核纤层解聚；使核仁蛋白磷酸化，促使核仁解体；促使细胞骨架重排；调整细胞形态。
3）G1/S 期转化：G1周期蛋白与CDK2、CDK4、CDK6.等CDK激酶
4）分裂中期向后期转化：M期CDK激酶可以激活APC。
19。 Please introduce why the concentration of receptors is important during
Activation of signal transportation.
20 The
balance of cell functions is necessary, could you use one signal pathway
to illustrate the activation and inhibition of signal transduction (which kind of
molecules are involved in this process.).
21 could you list the types of cell adhesions?
22 could you use one cell adhesion molecule and its ECM to introduce
the signal transduction from outside to inside?
23 why the cytoskeleton organization (actin) is important for cell adhesions?