医学遗传学词汇英语术语英文(Glossary) 8
Relative risk --- A comparison of the risk for a disease or trait in individuals who share a particular factor (such as genotype, an environmental exposure, or a drug) versus the risk among individuals who lack the factor.
Affected Unaffected Total
Factor present a b a+b
Factor absent c d c+d
Total a+c b+d a+b+c+d
The risk of being affected in individuals who have the factor =(a/a+b), the risk of being affected when the factor is absent =(c/c+d), and the relative risk ratio =(a/a+b)/(c/c+d)=a(c+d)/c(a+b). Note that relative risk ratio ≈ad/bc, the odds ratio, when the disease is relatively rare (c<<d and a<<b). See odds ratio.
相对风险：某因素对某性状或患病的效应强度。通过比较疾病或性状组与正常对照组的基因型、环境接触因子或药物等特定的因素，得出风险的比值。具体计算方法如下：
患病（性状）对照 合计
携带某因素 a b a+b
不携带某因素 c d c+d
合计 a+c b+d a+b+c+d
患病组携带某因素的风险=(a/a+b)，患病组不携带某因素的风险=(c/c+d)，故相对风险值=(a/a+b)/(c/c+d)=a(c+d)/c(a+b)。注意，当疾病相对罕见时（c<<d，a<<b），相对风险值≈ad/bc，等同于比值比。参见比值比。
Relative risk ratio (λr) --- In complex disorders, the risk that a disease will occur in a relative of an affected person compared with the risk for disease in any random person in the general population.
相对风险比值（λr）：在复杂疾病中，患者亲属罹患疾病的风险与一般个体风险的比值。
Repetitive DNA (repeats) --- DNA sequences that are present in multiple copies in the genome.
重复DNA：基因组中有多份拷贝的DNA序列。
Replication error positive --- A phenotype of cancer cells in which loss of function of mismatch repair genes causes errors such as slipped mispairing to go unrepaired when microsatellite sequences are replicated. These errors lead to tissue mosaicism so that the cancer appears to contain more than two alleles at many short tandem repeat polymorphic loci.
阳性复制差错：癌细胞的一种表型，即在微卫星DNA序列发生重复扩增时，错配修复基因功能的丢失所引起的差错（如滑脱错配）无法得到修复。这些复制差错导致组织镶嵌现象，故癌症的许多短串联重复多态性基因座上有2个以上的等位基因。
Replicative segregation --- Random distribution of mitochondria into daughter cells.
复制分离：线粒体随机分布到子细胞当中。
Repulsion --- Describes the phase of two alleles at two different but syntenic loci, in which one allele at one of the loci is not on the same chromosome as the allele at the second locus. See phase and coupling.
互斥相：描述2个同线性基因座上的2个等位基因排列关系的术语。如一个显性基因与另一个基因座的隐性基因连锁时其杂合体的排列方式为Ab/aB。参见相和互引相。
Restriction endonuclease (restriction enzyme) --- An enzyme, derived from bacteria, that can recognize a specific sequence of DNA and cleave the DNA molecule within the recognition site or at some nearby site.
限制性内切酶（限制酶）：特异识别短的DNA序列并且切割耙位点或别处的DNA双链酶。
Restriction fragment length polymorphism (RFLP) --- A polymorphic difference in DNA sequence between individuals that can be recognized by restriction endonucleases. See polymorphism.
限制性片段长度多态性：同一物种的亚种、品系或个体间基因组DNA受同一种限制性内切酶作用而形成不同酶切图谱的现象。参见多态性。
Restriction map --- A linear array of sites on DNA cleaved by various restriction endonucleases.
限制图：标明DNA分子上的限制位点、数目、限制片段大小以及排列顺序的图谱。
Restriction site --- A short sequence in DNA that can be recognized and cut by a specific restriction endonuclease.
限制位点：DNA分子中被限制性内切酶识别的碱基序列。
Retrovirus --- A virus, with an RNA genome, that propagates by conversion of the RNA into DNA by the enzyme reverse transcriptase.
反转录病毒：能编码反转录酶的RNA病毒。病毒RNA基因组可反转录为病毒DNA，并整合在宿主染色体中一同复制。
Reverse transcriptase --- An enzyme, RNA-dependent DNA polymerase, that catalyzes the synthesis of DNA on an RNA template.
反转录酶：以RNA为模板催化合成DNA的酶。
RFLP --- See restriction fragment length polymorphism.
RFLP：参见限制性长度多态性。
Ribonucleic acid --- See RNA.
核糖核酸：参见RNA。
Ribosome --- A cytoplasmic organelle composed of ribosomal RNA and protein, on which polypeptides are synthesized from messenger RNA.
核糖体：由核糖体RNA和蛋白质组成的细胞器，协助mRNA合成多肽链。
Ring chromosome --- A structurally abnormal chromosome in which the telomere of each chromosome arm has been deleted and the broken arms have reunited in ring formation.
环状染色体：呈环状的染色体。为一种染色体结构异常。
Risk --- The probability of an event’s occurring. Often calculated as the number of times the event occurs divided by the total number of opportunities there were for the event to occur. As with all probabilities, risk varies from 0 to 1.
风险：某事件发生的概率。大小范围为0～1。
RNA (ribonucleic acid) --- A nucleic acid formed on a DNA template, containing ribose instead of deoxyribose. Messenger RNA (mRNA) is the template on which polypeptides are synthesized. Transfer RNA (tRNA), in cooperation with the ribosomes, brings activated amino acids into position along the mRNA template. Ribosomal RNA (rRNA), a component of the ribosomes, functions as a nonspecific site of polypeptide synthesis.
RNA（核糖核酸）：由4种核糖核苷酸经磷酸二酯键连接而成的长链聚合物，是遗传信息的载体。包括信使RNA (mRNA)、 转移RNA (tRNA) 和核糖体RNA (rRNA)。
RNA polymerase --- An enzyme that synthesizes RNA on a DNA template.
RNA聚合酶：以DNA或RNA为模板合成RNA的酶。
RNAi --- RNA interference. A system for regulating gene expression in which short RNA segments, approximately 22 bases in length, form double-stranded structures with an mRNA and either target it for destruction or block its translation. (See microRNA.) Scientists have taken advantage of this normal, endogenous system of gene regulation to design new and powerful technologies for gene silencing by use of exogenously supplied RNAi sequences.
RNA干扰：双链RNA有效地阻断靶基因表达的现象。参见微RNA。
Robertsonian translocation --- A translocation between two acrocentric chromosomes by fusion at or near the centromere, with loss of the short arms.
罗伯逊易位：两条近端着丝粒染色体之间的相互易位。在着丝粒附近断裂，两条长臂通过着丝粒融合为一条大染色体，两条短臂则连接成一条小染色体。
Sanger sequencing --- Currently, the method most widely used to determine the nucleotide sequence of a DNA molecule. The DNA whose sequence is to be determined is used as a template for a polymerase that extends a complementary primer in the presence of four different dideoxynucleotides (“chain-terminating” nucleotides) corresponding to the four bases, ACGT, found in DNA. The length of the strands produced corresponds to which dideox-ynucleotide was incorporated and terminated the extension reaction and therefore what base was present in the template at that site in the molecule (see Fig. 4-11).
Sanger测序法：最常用的测定DNA分子序列的方法。以被测序的DNA分子为模板，引物先与模板复性，然后将反应物分成4份，各加脱氧核苷三磷酸和双脱氧核苷三磷酸，使每管中有不同的ddNTP，由于ddNTP不能再加dNTP，故链延伸即终止。从而得到长短不一的片段，可读出待测核苷酸链的全部序列（参见图4-11）。
Satellite DNA --- DNA containing many tandem repeats of a short basic repeating unit; not to be confused with chromosomal satellite, the chromatin at the distal end of the short arms of the acrocentric chromosomes.
卫星DNA：高度重复的DNA序列，重复单元长短不一，主要分布在染色体着丝粒的异染色质区。注意不要与染色体随体混淆。
Scaffold --- The nonhistone structure observed when histones are experimentally removed from chromosomes. Believed to represent a structural component of the nucleus and of chromosomes.
支架：组蛋白从染色体移除后的非组蛋白结构。是细胞核和染色体的结构之一。
Segmental aneusomy --- Loss of a small segment from one chromosome of a pair, resulting in hemizygosity for genes in that segment on the homologous chromosome. See also contiguous gene syndrome.
节段异体：染色体小节段丢失所导致的该同源染色体节段基因的半合子。参见邻接基因综合征。
Segmental duplication --- See segmental aneusomy.
节段重复：参见片段异体。
Segregation --- In genetics, the disjunction of homologous chromosomes at meiosis.
分离：在遗传学中，指减数分裂时同源染色体的分离
Segregation analysis --- A statistical method that assesses the phenotypes of individuals in families to determine the most likely mode of inheritance of a disease or trait.
分离分析：评估家系成员表型的统计学方法，以确定疾病或性状最有可能的遗传方式
Selection --- In population genetics, the operation of forces that determine the relative fitness of a genotype in the population, thus affecting the frequency of the gene concerned.
选择：不同基因型（或个体）具有不同的繁殖力或生活力的现象。
Sense strand --- See coding strand.
有义链：参见编码链。
Sensitivity --- In diagnostic tests, the frequency with which the test result is positive when the disorder is present.
灵敏度：在诊断性检测中，阳性检测结果的准确性。
Sequence --- 1. In genomics and molecular genetics, the order of nucleotides in a segment of DNA or RNA. 2. In clinical genetics, a recognizable pattern of dysmorphic features due to a number of different causes; to be distinguished from malformation syndrome.
序列：1. 在基因组学和分子遗传学中，指DNA或RNA的核苷酸序列。2. 在临床遗传学中，指因各种原因所导致的畸形的类型。与畸形综合征不同。
Sex chromatin --- See Barr body.
性染色质：参见Barr小体。
Sex chromosomes --- The X and Y chromosomes.
性染色体：X和Y染色体。
Sex-influenced --- A trait that is not X-linked in its pattern of inheritance but is expressed differently, either in degree or in frequency, in males and females.
从性性状：决定性状的基因位于常染色体上，在雌、雄性别中有不同的表型。
Sex-limited --- A trait that is expressed in only one sex, although the gene that determines the trait is not X-linked.
限性性状：某一特定表型只限于在一种性别中表现的遗传现象，并非都是X-连锁基因。
Sex-linked --- Old term for X-linked, now little used because formally it fails to distinguish between X and Y linkage.
性连锁：X-连锁的旧称。位于性染色体上的基因的遗传现象。
Short tandem repeat polymorphism (STRP) --- A polymorphic locus consisting of a variable number of tandemly repeated binucleotide, trinucleotide, or tetranucleotide units such as (TG)n, (CAA)n, or (GATA)n; different numbers of units constitute the different alleles. Also termed a microsatellite marker.
短串联重复序列多态性（STRP）：头尾衔接的短串联重复序列由于重复单元的重复数目不同而造成的DNA多态现象。又称微卫星标记。
Sib, sibling --- A brother or sister.
同胞：兄弟姐妹。
Sibpair analysis --- A form of model-free linkage analysis in which pairs of siblings either concordant or discordant for a phenotype or trait are analyzed at loci throughout the genome to determine whether there are any loci at which they share alleles significantly more or less than the expected average of 50%.
同胞对分析：利用全同胞对的标记基因和表型信息进行连锁分析的方法
Sibship --- All the sibs in a family.
同胞群：由全同胞和半同胞组成的群体。
Silencer --- A DNA sequence that acts in cis (i.e., on the same chromosome) to decrease transcription of a nearby gene. The silencer may be upstream or downstream to the gene and may be in the same or the reverse orientation (contrast with enhancer).
沉默子：帮助降低或关闭邻近基因表达活性的一段DNA顺式元件序列。相对于增强子。
Silent allele --- A mutant gene that has no detectable phenotypic effect.
沉默等位基因：一类突变基因。通常不表达，但在肿瘤细胞中呈现转录活性的基因。
Single-copy DNA --- The type of DNA that makes up most of the genome.
单拷贝DNA：每一单倍体基因组中只出现一次的基因或DNA序列。
Single-gene disorder --- A disorder due to one or a pair of mutant alleles at a single locus.
单基因病：由单个基因发生突变引起的遗传病。
Single nucleotide polymorphism (SNP) --- A polymorphism in DNA sequence consisting of variation in a single base.
单核苷酸多态性（SNP）：同一物种不同个体基因组DNA的等位序列上单个核苷酸存在差别的现象。
Sister chromatid exchange --- The exchange of segments of DNA between sister chromatids, either in the four-strand stage of meiosis or in mitosis. Occurs with particularly high frequency in patients with Bloom syndrome.
姐妹染色单体交换：发生在姐妹染色单体之间的交换，可见于减数分裂的四分体时期或有丝分裂。Bloom综合征患者常见姐妹染色单体交换。
SKY --- See spectral karyotyping.
SKY：参见光谱核型。
Slipped mispairing --- A mutational mechanism that occurs during DNA replication of sequences with repeats of one or more nucleotides, in which a repeat on one strand mispairs with a similar repeat on the complementary strand, generating a deletion or expansion of the number of repeats.
滑脱错配：DNA序列上重复片段的一种复制突变。一条链上的重复，与互补链上相似的重复发生错配，使得重复次数缺失或扩增。
SNP --- See single nucleotide polymorphism.
SNP：参见单核苷酸多态性。
Solenoid --- A fiber composed of compacted strings of nucleosomes, forming the fundamental unit of chromatin organization.
螺旋管：核小体串珠压缩整合而成的一种纤维结构，形成染色质结构的功能单位。
Somatic mutation --- A mutation occurring in a somatic cell rather than in the germline.
体细胞突变：发生在体细胞而非种系中的可遗传的变异。
Somatic rearrangement --- Rearrangement of DNA sequences in the chromosomes of lymphocyte precursor cells, thus generating antibody and T-cell receptor diversity.
体细胞重排：淋巴祖细胞染色体的DNA序列重排，产生抗体和T细胞受体多态性。
Southern blotting --- A technique, devised by the British biochemist Ed Southern, for preparation of a filter to which DNA has been transferred, following restriction enzyme digestion and gel electrophoresis to separate the DNA molecules by size. Specific DNA molecules can then be detected on the filter by their hybridization to labeled probes.
DNA印迹法：变性DNA从电泳凝胶通过毛细管作用转移到纤维素膜等固相介质上，然后进行DNA杂交的操作过程。
Specialty proteins --- Proteins, expressed in only one or a limited number of cell types, that have unique functions contributing to the individuality of the cells in which they are expressed. Contrast with housekeeping proteins.
特种蛋白：只在一些细胞类型中表达的蛋白，在表达的细胞中具有特异功能。参见持家蛋白。
Specification --- The first stage of commitment in which a cell will follow its developmental program if it is explanted but can still be reprogrammed to a different fate if it is transplanted to a different part of the embryo.
特化：细胞或组织在离体培养的中性环境中仍按原先被定型的命运自主地进行分化。
Specificity --- In diagnostic tests, the frequency with which a test result is negative when the disease is absent.
特异性：在诊断性检测中，阴性检测结果结论正确的比例。