遗传学名词解释I

I

identical twins -- See monozygotic twins.

Ig -- See immunoglobulin.

imaginal disc -- Discrete groups of cells set aside during embryogenesis in holometabolous insects which are determined to form the external body parts of the adult.

immunoglobulin -- The class of serum proteins having the properties of antibodies.

inborn error of metabolism -- A biochemical disorder that is genetically controlled; usually an enzyme defect that produces a clinical syndrome.

inbreeding -- Mating between closely related organisms.

inbreeding depression -- A decrease in viability, vigor, or growth in progeny following several rounds of inbreeding.

incomplete dominance -- Expression of heterozygous phenotype which is distinct from, and often intermediate to, that of either parent.

incomplete linkage -- Occasional separation of two genes on the same chromosome by a recombinational event.

independent assortment -- The independent behavior of each pair of homologous chromosomes during their segregation in meiosis I. The random distribution of maternal and paternal homologs into gametes.

inducer -- An effector molecule that activates transcription.

inducible enzyme system -- An enzyme system under the control of a regulatory molecule, or inducer, which acts to block a repressor and allow transcription.

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initiation codon -- The triplet of nucleotides (AUG) in an mRNA molecule that codes for the insertion of the amino acid methionine as the first amino acid in a polypeptide chain.

insertion sequence -- See IS element.

in situ hybridization -- A technique for the cytological localization of DNA sequences complementary to a given nucleic acid or polynucleotide.

intercalary deletion -- A form of chromosome deletion where material is lost from within the chromosome. Deletions that involve the end of the chromosome are called terminal deletions.

intercalating agent -- A compound that inserts between bases in a DNA molecule, disrupting the alignments and pairing of bases in the complementary strands (e.g., acridine dyes).

interference -- A measure of the degree to which one crossover affects the incidence of another crossover in an adjacent region of the same chromatid. Negative interference increases the chances of another crossover; positive interference reduces the probability of a second crossover event.

interphase -- That portion of the cell cycle between divisions.

intervening sequence -- See intron.

intron -- A portion of DNA between coding regions in a gene which is transcribed, but which does not appear in the mRNA product.

inversion -- A chromosomal aberration in which the order of a chromosomal segment has been reversed.

inversion loop -- The chromosomal configuration resulting from the synapsis of homologous chromosomes, one of which carries an inversion.

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in vitro-- Literally, in glass; outside the living organism; occurring in an artificial environment.

in vivo-- Literally, in the living; occurring within the living body of an organism.

IS element -- A mobile DNA segment that is transposable to any of a number of sites in the genome.

isoagglutinogen -- An antigenic factor or substance present on the surface of cells that is capable of inducing the formation of an antibody.

isochromosome -- An aberrant chromosome with two identical arms and homologous loci.

isolating mechanism -- Any barrier to the exchange of genes between different populations of a group of organisms. In general, isolation can be classified as spatial, environmental, or reproductive.

isotopes -- Forms of a chemical element that have the same number of protons and electrons, but differ in the number of neutrons contained in the atomic nucleus.

isozyme -- Any of two or more distinct forms of an enzyme that have identical or

nearly identical chemical properties, but differ in some property such as net electrical charge, pH optima, number and type of subunits, or substrate concentration.

Identical l(monozygotic) twins 同卵双生子：由一个受精卵经第一次卵裂产生两个单独的细胞，并发育成正常个体。同卵双生子的遗传背景完全相同。

Imaginal discs 器官芽、成虫盘：在果蝇的囊胚中，一些未分化的细胞将发育为成体的组织和器官。

immunoglobulins(1G) 免疫球蛋白：通过B细胞分泌的一种特殊的蛋白(抗体)，存在于血液和淋巴系统中，它们负责体液免疫。

inbreeding 近交：亲缘关系很近的个体之间交配。

Inbreeding coefficient 近交系数；同一个祖先的一个基因拷贝在某后代中得到纯合的概率。Incomplete dominance 不完全显性：杂合子(Aa)的表型显示出介于两种纯合(AA和aa)的表型之间的状况。

Independent tassortment 自由组合<盂德尔第二定律)，即不连锁的非等位基因在形成配子时自由组合。

Induced mutation 诱发突变：由于诱变剂的处理而产生的突变。

inducer 诱导物：一种环境因于能触发操纵子的转录。

induction 诱导：解除阻遏物对一个基因或一组基因的负控制。

Insertion sequence(ⅡS) 插入序列：在原核生物中的一种最简单的转座因子，它插入基因后使基因失活，它不带有抗性基因。

interference 干涉：染色体发生的第一次交换抑制了邻近区域的第二次交换。

Intergenic suppressor 基因间抑制：一种基因突变效应抑制另一个基因突变的表型后果，而这两个基因的位置是不同的。

Internal control region(1CR) 内部控制区：RNA聚合酶Ⅲ识别的启动于序列，它位于基因的内部，如真核生物的tRNA基因和5SrRNA基因。

Interrupted mating 中断杂交作图：通过搅拌来中断细菌的杂交，以确定不同时间内供体中基因进入受体的概率来对染色体作图。

Intervening sequence(1vs) 间插序列：即内含子，位于基因内部，不编码基因产物，在成熟mRNA中被切除。

Intrachromosomal recombination 染色体内重组：两对基因之间的杂交形成的重组，即姊妹染色体之间的重组。

intron 内含子：见interveningsequence。

inversion 倒位：一种和染色体结构有关的突变，即染色体上某片段在原来位置上发生180 翻转。

Inverted repeat(ⅡR) sequence 反向重复序列：序列相同但方向相反的序列，常存在于转座因子的两端。

Isoaccepting tRNA 同工tRNA：携带同一种特定氨基酸的各种tRNA分子。isochromosome 等臂染色体：一种畸变产生的染色体，两臂的长度和结构完全相同。isogenicstrain 纯合品系：一组基因型相同的个体。