Saturday, January 15, 2011

Something maybe useful to u..

something related to Bio 5 Edexcel Scientific article A BIT...=))


AP Biology Chapter 18 Regulation of Gene Expression

PROKARYOTIC GENE EXPRESSION

·         Operator- segment of DNA that serves as a switch for gene expression
·         Operon- entire stretch of DNA required for enzyme production; several DNA sequences controlled as a unit
·         Repressor- protein that can switch off the operon by binding to the operator
·         Regulatory gene- gene located some distance from the operon it controls & has its own promoter
·         Corepressor- small molecule that cooperates with a repressor protein to switch an operon off; often a substrate

Figure 18.3 Page 353 (trp operon)

trp operon is a repressible operon – transcription is on until repressed by presence of substrate
lac operon is an inducible operon – transcription is off until activated by presence of substrate

·         Inducer- small molecule that inactivates the repressor

     Figure 18.4 Page 354 (lac operon)

·         Cyclic AMP (cAMP)- cyclic adenosine monophosphate; regulator in lac operon; accumulates when lactose is scarce
·         Activator – protein that binds to DNA and stimulates transcription of a gene

EUKARYOTIC GENE EXPRESSION

Transcriptional Control

·         Differential gene expression – expression of different genes by cells with the same genome
·         Histone acetylation – acetyl groups are attached to lysines in histone tails; acetylated lysines no longer bind to neighboring nucleosomes – transcription is easier

Histones can also be methylated – addition of methyl groups

·         Genomic imprinting – methylation permanently regulates expression of genes from either male or female parent
·         Epigenetic inheritance – inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence; alterations not in DNA, but chromatin structure
·         Control elements – segments of noncoding DNA that help regulate transcription by binding certain proteins
·         Enhancers – thousands of nucleotides upstream or downstream of a gene

Post Transcriptional Control

One gene can produce thousands of different proteins depending on mRNA processing

·         Alternative RNA splicing – different mRNA molecules produced from the same primary transcript; depends on which segments are ‘introns’ & which are ‘exons’

mRNA degradation – mRNA has a life span that differs b/t organisms – longer life spans help adaptability

Initiation of translation – inhibitory action of a protein – blocks translation
Protein activation – polypeptides must be processed into active final products
Protein breakdown – length of time a protein is functional; regulated by selective degradation

·         Proteasomes – protein complexes that recognize tagged proteins and degrade them

·         MicroRNAs (miRNAs) –  single strand RNA; capable of binding to complementary sequences in mRNA molecules; blocks translation
·         RNA interference (RNAi)- silencing of gene expression using double-stranded RNA to trigger breakdown of a gene’s mRNA
·         Small interfering RNAs (siRNAs)- small, single strand RNA; generated from double strand RNA; acts as an miRNA

·         Cell differentiation – process by which cells become specialized in structure and function
·         Morphogenesis – physical processes that give an organism its shape
·         Cytoplasmic determinants – maternal substance in egg that influence the course of early development
·         Induction – signals cause change within target cells
·         Pattern formation – cytoplasmic determinants and inductive signals contribute to spatial organization of tissues and organs
·         Positional information – cues that tell a cell its location relative to body axes and neighboring cells to determine how cell responds to signals
Fruit Fly Gene Specifics
·         Homeotic genes – control pattern formation in embryo, larva & adult
·         Embryonic lethals – mutations w/ phenotypes that cause death at embryonic or larval stage
·         Maternal effect gene – when mutant in mother results in a mutant phenotype in offspring
·         Egg-polarity genes – genes that control orientation
·         Morphogens – establish an embryo’s axes and other features of its form

Cancer and Genes
·         Oncogenes – cancer causing genes
·         Proto-oncogenes – normal versions of cellular genes
·         Tumor-suppressor genes – genes that encode proteins that help prevent uncontrolled cell growth
·         Ras gene – gene that encodes a protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle
·         P53 gene – tumor suppressor gene

感动的霎那

不曾想象自己会去戏院看这类型的电影
家庭剧?本地片?开玩笑……
阴差阳错下,我看了这套戏

后悔?我也说不上,
心情,回到kl压郁的不良情绪一次性爆发
在戏院里,说不上哭了多少回
只懂出了戏院,眼睛很痛,
他们说我眼睛红了,肿了。

下次,要是心情不好
说不定我会独自去戏院
看半夜场,宣泄自己的情绪。
这样也是不错的发泄方式。

哭,不是我喜欢的方式,
但是要是没有别的办法
我想哭,狠狠地哭,
去别人看不见的地方尽情地哭
至少听见,看见我流泪的人
是要陌生人……

绝对不会在我喜欢的人面前
流一滴眼泪,
不哭不是因为不喜欢他,不信任他
而是太在乎他,不想他难过担心想太多
喜欢就是那么地简单,
当你想为他做的东西比自己多^^

Saturday, January 1, 2011

挥别2010 · 我长大了!!

2010 年,就这样从我的眼前溜走。很是不舍,但是也无可奈何。日子,活着就是要过的,人是向前看的,而不是往后眺望,有云,:往事不可谏,来者犹可追。

2010, 我看见很多东西,让我学了很多,体会更多。很多事情,往往你不会了解它的严重性,或是后果,若你不曾体会。这一年来,尝试了一些我根本不应该参与的事情,得到了一些我不想得到的东西。不听话的孩子,就是会有不一样的收获……(自嘲)

期待2011到来的同时,我心里更存在着我对朋友的感激。你们对我的好,我是会察觉并珍惜。很多时候,我会忽略身边一直在守护着我的朋友,因为他们太好了,我常常会将之视为理所当然。开始变得不珍惜眼前的一切,开始要求更多,开始无理取闹,开始变成一位很白痴的人。我很清楚,很明白我是一个不足的人,很多时候都得靠朋友填满我的空缺。眼前的美好一度让我忘了身边的你们,梦醒了,发现现实没有童话般的完美。庆幸的是,泪湿的眼眶前,还有你们伸出的援手。

朋友阿,是我在2010发掘的宝。无价的。老实说,你们也因为有我,日子才那么大发光彩的吧~都让你们看到我不堪的一面,很难得吧,那么伟大、坚强、后知后觉兼天塌下来也不理的我,也会有那么楚楚动人的一面…… 哈哈哈,我功不可没哦!我明白乐观,开朗,整天把笑脸往脸上挂的,才是你们期待的我,我会尽量办到的啦,因为,我可是周芷琦。呵呵,不让期待的眼神落空。

2010年,让我真正体会到健康的重要,朋友阿,孩子们,健康往往是在我们不留神时流失的。不健康的身体,可是会让一切的努力白费。某位我很敬爱的亲戚在年中,被症断出患有乳癌的噩耗。很晴天霹雳,但是也无可奈何,但是也必须去面对。人生就是那么的无奈,很多时候我们没有选择的余地,因为我们是渺渺的人类。我也有我必须面对的健康问题,所以才会感触。都说了,人是在遇到问题时,才懂得珍惜。你就别问是什么问题了,隐私!

2010,我度过了二十岁前的大关。为了闯这关,我费了很多力气,泪水,心酸还有心疼。在意识到可能要面对问题,我选择了逃避的方式,我没有勇气与信心去面对。怎知,逃避反而让我正面去迎接另一个更大的关。哈哈,天意难违。很后悔当初要去接近这扇门,很天真地以为门后有桃源。其实不然,是一个能煎熬人心的地狱。被背叛的人才会懂得背叛人的可憎度,背叛人的人自己也会有地狱等她,所以活在世上要对得起天地良心。闯关后都会有得到宝物吧,这就是2010得到的另一个宝典。患难见真情,哈哈,老套的话恰恰是我今年的写照。朋友,虽然有让我心寒的,但正是心寒的让我发现何为真正的朋友。(不用暗爽拉)


2010,我学会要珍惜生命。
2010,我学会要坚强懂事
2010,我学会要勇敢面对,逃避解决不了问题
2010,我学会要惜福,幸福不是必然的
2010,我学会要精打细算,钱得来不易
2010,我学会朋友是家外的靠山
2010,我学会放下,不要太执着,最后会得不偿失,因为分离/失去是必然的。

其实,对2010我没有太多的好感,毕竟发生太多不愉快的事,是不幸的一年,能回忆的乐事似乎也不怎么多。但是人要保有知足的心啊,所以今年我很开心,很满足了,期待会有更美好的明天。2011年,我仍会继续冲的!!

PS:2010真地让我变成熟很多涅~挫折让人变得更坚强。
还有,爱我的人们,我也爱你!大爱大爱!!