mRNAs.
Mutation DNA damage that causes a heritable change in the DNA.
Negative regulation With respect to transcription, means that the binding of a protein causes repression of transcription.
Nitrogenous base One or two-ringed molecules that are an important 突变
使DNA发生可遗传变化的DNA损伤。 负调控 关于转录，意思是当一种蛋白质结合上去以后引起转录的阻遏。
含氮碱基
一种一个环或两个环的分子，是核酸的重
component of nucleic acids. Each ring has a number of nitrogen atoms.
Nitrous acid A mutagenic chemical that causes deamination and conversion of several bases into abnormal bases.
Non-homologous end joining (NHEJ) A form of double-stranded break repair in which broken ends are directly rejoined, without using homologous recombination.
Non-homologous recombination Rearrangement of DNA regions that are not similar (homologous) to each other.
Non-LTR retrotransposons see LTR retrotransposons. Non-LTR retrotransposons do not have long terminal repeats, and integrate into DNA using a completely different mechanism.
Nonsense mutation A point mutation that introduces a stop codon before the normal stop codon of the gene. In normal English, ‘nonsense’ = something that has no meaning. The introduction of a stop codon is a serious mutation, and often leads to mRNAs that cannot be transcribed or that make seriously damaged proteins.
Northern blotting A technique to identify individual RNA molecules after gel electrophoresis. Name origin: the word ‘Northern’ here is a play on words. The first such technique to be developed was for DNA. It was called a Southern blotting because the scientist who developed the technique was named Southern. Southern is also a word that indicates direction. When a similar technique was developed for RNA, scientists wanted to give the technique a similar but different name, so they called it a Northern blotting. ‘Northern’ is not anybody’s last name, but it is the opposite direction as ‘southern’.
N-terminus The end of a protein containing a free amino group. The ‘N-’ derives from the fact that amino groups contain nitrogen.
要组成部分。每个环有几个氮（nitrogen）原子。
亚硝酸
能引起脱氨基和将几种碱基转变成异常碱基的诱变性化学物质。
非同源末端连接（NHEJ） 一种双链断裂的修复形式，修复时将断头直接连接起来，不需要进行同源重组。 非同源重组
互相不相似的（即不同源的）DNA区域之间的重排。
非LTR反转录转座子
参照‘LTR反转录转座子’。非LTR反转录转座子没有长末端重复序列，采用完全不同的机理整合到DNA中。 无义突变
在基因的正常终止密码子之前产生一个终止密码子的点突变。在日常英语中，‘nonsense’ = 没有意义的事物。产生终止密码子是一种严重的突变，常常导致mRNA不能被转译或产生严重损坏的蛋白质。
Northern印迹法
在凝胶电泳后对单个RNA分子进行鉴定的技术。名称来源：‘Northern’在这儿是个双关语。第一种这样的技术是用在DNA上的。它被称为Southern印迹法，因为发展出这一技术的科学家名叫Southern。Southern（南方的）也是一个指方向的词。当在RNA上发展出类似的技术时，科学家想为它取一个类似的、但又不同的名称，所以他们把它叫做Northern印迹法。‘Northern’ 不是任何人的姓，它是‘southern’的对应词。
N末端
蛋白质的含有自由氨基的末端。‘N-’来自于氨基中含有氮（nitrogen）这一事实。
Nuclear pores Large protein complexes in the nuclear membrane that allow molecules to pass between the nucleus and the cytoplasm. A ‘pore’ = a small hole in a surface.
Nucleic acids Macromolecules that are polymers of nucleotides. They are acidic because of the phosphodiester bond, and are found in high concentrations in the nuclei of 核孔
核膜上的大的蛋白质复合体，允许分子在细胞核与细胞质之间通行。‘pore’ = 表面上的小孔。
核酸
一种大分子，是核苷酸的聚合物。由于它们含有磷酸二酯键，所以它们是酸性（acidic）的，并且在细胞核（nuclei）中cells.
Nucleosome A structure with DNA wrapped around a core of histones. In normal English, ‘nuclear’ = ‘core’.
Nucleotide excision repair (NER) A kind of excision repair usually used to fix nucleotides that have undergone large or unusual modifications.
Nucleotides Small molecules that can be polymerized to form nucleic acids.
Nucleus The compartment of eukaryotic cells that houses most of the DNA. In normal English, ‘nucleus’ = ‘core’ or ‘center’. The nucleus of an atom is the small core of protons and neutrons.
Okazaki fragments Individual pieces of newly synthesized DNA created during discontinuous synthesis. Okazaki is the name of the scientist who discovered these fragments.
Operator DNA element in prokaryotes downstream of the promoter. Binding site for proteins that regulate transcription. In normal English, an ‘operator’ = somebody who controls a system.
Operons An organization of related genes in which all genes are under the control of one regulatory region and are expressed on one mRNA transcript.
OriC
The origin of replication on an E. coli chromosome.
Overexpression A technique in which a particular protein is expressed in a cell in large concentrations, over the normal concentration.
P (petpidyl) site Site on a ribosome to which a tRNA moves after being in the A site. In the P site, the bond that joins the tRNA to a polypeptide is broken, and the polypeptide is rejoined to the tRNA (+ amino acid) in the A site by a peptide bond.
以很高的浓度存在。
核小体
DNA包裹在组蛋白核心外面形成的结构。在日常英语中，‘nuclear’ = ‘核心’。 核苷酸切除修复（NER） 一种切除修复方法，通常用来修复经受了大的或不同寻常修饰的核苷酸。 核苷酸
能够聚合形成核酸的小分子。
细胞核
为大多数DNA提供停留场所的真核细胞内的隔离空间。在日常英语中，‘nucleus’ = ‘核心’或‘中心’。原子的核是由质子和中子组成的小核心。
冈崎片段
在不连续合成中产生的新合成的单独DNA片段。冈崎是发现这些片段的科学家的姓名。
操纵基因
原核生物中位于启动子下游的DNA元件。是转录调控蛋白的结合位点。在日常英语中，‘operator’ = 控制某一系统的人。 操纵子
一种相关基因的组织方式，其中所有基因位于一个调控区域的控制之下并且被表达成一个mRNA转录本。
OriC
大肠杆菌染色体（chromosome）上复制的起点（origin）。
过量表达
一种在细胞中大量表达（expressed）某种特殊蛋白的技术，其表达量超出了（over）正常的浓度。
P（肽基）位
核糖体上的一个位置，是tRNA从A位移出后所处的位置。在P位上，tRNA与多肽链之间的连接被打断，之后此多肽链与A位上的tRNA（+氨基酸）之间形成肽键。
Partial diploids Organisms to which an extra set of certain genes has 部分二倍体
指一些特殊的生物，其体内的一些基因有been added (see diploid).
Peptide
A term often used to denote a small polypeptide. Peptide bond
The bond that connects amino acids in a polypeptide.
Peptidyl transferase The enzyme functioning in ribosomes that transfers the polypeptide from the P site tRNA to the A site tRNA (+ amino acid), creating a new peptide bond.
Phosphodiester bond A bond joining nucleotides in a nucleic acid. The bond contains one phosphorous atom, and two ester bonds. The prefix ‘di-’ = ‘two’.
Photolyase Enzyme that directly reverses pyrimidine dimers, which usually are caused by UV light. Prefix ‘photo’ = ‘light’.
Point mutations Mutations to individual bases in DNA, usually leading to substitution of a base with another base. In normal English, a ‘point’ = something very small and precisely localized. Likewise, point mutations only occur to single bases, a very small part of the whole DNA molecule.
Poly(A) polymerase Specialized RNA polymerase that adds many adenine nucleotides to the end of pre-mRNAs to form the poly(A) tail.
Poly(A) tail A post-transcriptional addition to mRNA in eukaryotes that involves addition of many adenine (A) nucleotides to the 3’ end of the transcript. Prefix ‘poly-’ = ‘many’.
Polycistronic mRNA mRNA in prokaryotes that contains more than one gene to be translated. Cistron = gene. Prefix ‘poly-’ = ‘many’ or ‘more than one’.
Polymerase chain reaction (PCR) A technique used to replicate specific regions of a DNA template many times. A chain reaction = reaction that grows larger and larger over time. With each cycle of PCR, the amount of DNA copies produced grows almost exponentially.
Polymer
额外的一套拷贝（参照‘二倍体’）。 肽
时常用来说明小多肽的术语。 肽键
在多肽中连接氨基酸的键。
肽基转移酶
在核糖体中发挥作用的一种酶，它将P位tRNA上的多肽转移（transfer）到A位的tRNA（+氨基酸）上，产生新的肽（peptide）键。
磷酸二酯键
在核酸中连接核苷酸的键。该键含有一个磷原子和两个酯键。前缀‘di-’ = ‘二’。 光解酶
直接逆转嘧啶二聚体突变（通常由UV光线引起）的酶。前缀‘photo’ = ‘光’。 点突变
DNA中单个碱基的突变，通常造成某个碱基被另一个碱基替换。在日常英语中，‘point’ = 很小、很精确地定位的事物。同样，点突变只发生在单个的碱基上，在整个DNA分子很小的部分上。
Poly(A)聚合酶
在前体mRNA的末尾加上许多腺嘌呤核苷酸以形成poly(A)尾的特殊酶。 Poly(A)尾
真核生物在转录后加在mRNA 3’末端后面的许多腺嘌呤（A）核苷酸。前缀‘poly-’ = ‘许多’。
多顺反子mRNA
含有不止一个需转译基因的原核生物mRNA。cistron（顺反子） = 基因。前缀‘poly-’ = ‘许多’或‘不止一个’。
聚合酶链式反应（PCR）
一种用来对DNA模板上特殊区域进行许多次复制的技术。链式反应 = 随时间推移变得越来越多的反应。经过每一循环的PCR，产生出的DNA量几乎以指数形式增长。
聚合物
Macromolecule created by linking many smaller molecules. Prefix ‘poly-’ = ‘many’. Suffix ‘-mer’ = ‘subunits’ or ‘smaller components’.
Polypeptide
A polymer of amino acid connected by peptide bonds.
通过连接许多小分子而产生出的大分子。前缀‘poly-’ = ‘许多’。 后缀‘-mer’ = ‘亚基’或‘更小的组分’。
多肽
氨基酸由肽键连接在一起形成的聚合物。 多核糖体
一种转译复合体，其中有多个核糖体同时Polysome
A translation complex in which multiple ribosomes are translating one mRNA at the same time. Prefix ‘poly-’ = ‘many’ or ‘more than one’.
Positive regulation In reference to transcription, denotes the activation of transcription by binding of a protein.
Pre-initiation complex The group of general transcription factors II (TFIIs) and RNA polymerase II that assemble at the promoter of each Class II gene before initiation of transcription. Prefix ‘pre-’ = ‘before’.
Pre-mRNA The precursor to a eukaryotic mRNA, which has been transcribed but has not yet undergone post-transcriptional modifications. Prefix ‘pre-’ = ‘before’.
Pre-replicative complex (Pre-RC) Complex of proteins that mark origins of replication in eukaryotes and initiate replication. Often forms long before replication begins. Prefix ‘pre-’ = ‘before’.
Primary structure Amino acid sequence of a protein. Perhaps termed a ‘structure’ because the sequence is often enough to determine the folded structure of the protein.
Primary transcript see pre-mRNA. In normal English, a transcript = a copy of something. Primary = first. The primary transcript is the first RNA copy of the DNA, before any modifications have been made. Primase
The enzyme that adds primers to DNA.
Primers Short pieces of RNA that are hybridized to DNA so that DNA polymerase can initiate replication. Prefix ‘prim-’ = ‘first’. Primers must be made first, before DNA synthesis can begin.
Processivity The amount of DNA that DNA polymerase can replicate in one run, before falling off the template.
Promoter DNA element responsible for binding to RNA 在转译同一条mRNA。前缀‘poly-’ = ‘许多’或‘不止一个’。
正调控 关于转录，表示通过一种蛋白质的结合而激活转录。
前起始复合体
在转录起始前一组通用转录因子II（TFIIs）和RNA聚合酶II在每个II类基因启动子位置组装产生的结构。前缀‘pre-’ = ‘在……之前’。
前体mRNA
真核mRNA的前体，已经被转录出来但还没有经过转录后修饰。前缀‘pre-’ = ‘在……之前’。
前复制复合体（Pre-RC）
真核生物中标明复制起点并启动转录的蛋白质复合体。常常在复制开始前好久就形成了。前缀‘pre-’ = ‘在……之前’。 初级结构
蛋白质的氨基酸序列。称之为‘结构’的原因也许是因为这样的序列常常足以决定该蛋白质折叠出的结构。
初级转录物
参照‘pre-mRNA’。在日常英语中，a transcript = 某种事物的拷贝。primary = 第一、首先。初级转录物是DNA的第一个RNA拷贝，是在任何修饰发生前的拷贝。
引发酶
将引物加到DNA上去的酶。
引物
短的RNA片段，与DNA杂交以便DNA聚合酶启动转录。前缀‘prim-’ = ‘第一、首先’。在开始DNA合成前必须先有引物。 持续合成能力
DNA聚合酶在从模板上脱落前一次能够合成的DNA量的大小。
启动子
负责与RNA聚合酶结合的DNA元件（在
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