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dalton (Da) -- A unit of mass equal to that of the hydrogen atom, which is 1.67 x 10 - 24 gram. A unit ud in designating molecular weights.
Darwinian fitness -- See fitness.
deficiency (deletion) -- A chromosomal mutation involving the loss or deletion of chromosomal material.
degenerate code -- Term ud to describe the genetic code, in which a given amino acid may be reprented by more than one codon. Some amino acids (leucine) have six codons, others (isoleucine) have three, etc.
deletion -- See deficiency.
deme -- A local interbreeding population.
denatured DNA -- DNA molecules that have been parated into single strands.
de novo-- Newly arising; synthesized from less complex precursors rather than having been produced by modification of an existing molecule.
density gradient centrifugation -- A method of parating macromolecular mixtures by the u of centrifugal force and solutions of varying density. In buoyant density gradient centrifugation, using cesium chloride, the cesium solution establishes a gradient under the influence of the centrifugal field, and the macromolecules such as DNA diment in the gradient until the density of the cesium chloride solution equals their own.
deoxyribonuclea -- A class of enzymes that breaks down DNA into oligonucleotide fragments by introducing single-stranded breaks into the double helix.
deoxyribonucleic acid (DNA) -- A macromolecule usually consisting of antiparallel polynucleotide chains held together by hydrogen bonds, in which the sugar residues are deoxyribo. The primary carrier of genetic information.
deoxyribo -- The five-carbon sugar associated with the deoxyribonucleotides found in DNA.
dermatoglyphics -- The study of the surface ridges of the skin, especially of the hands and feet.
determination -- A regulatory event that establishes a specific pattern of future gene activity and developmental fate for a given cell.
diakinesis -- The final stage of meiotic propha I in which the chromosomes become tightly coiled and compacted and move toward the periphery of the nucleus.
dicentric chromosome -- A chromosome having two centromeres.
dideoxynucleotide -- A nucleotide containing a dexoyribo sugar lacking a 3' hydroxyl group. Stops further chai n elongation when incorporated into a growing polynucleotide; ud in the Sanger method of DNA quencing.falkirk
differentiation -- The process of complex changes by which cells and tissues attain their adult structure and functional capacity.
演讲稿格式dihybrid cross -- A genetic cross involving two characters in which the parents posss different forms of each character (e.g., tall, round x short, wrinkled peas).
diploid -- A condition in which each chromosome exists in pairs; having two of each chromosome.
diplotene -- A stage of meiotic propha immediately after pachytene. In diplotene, one pair of sister chromatids begins parating from the other, and chiasmata become visible. The overlaps move laterally toward the ends of the chromatids (terminalization).
directional lection -- A lective force that changes the frequency of an allele in a given direction, either toward fixation or toward elimination.
discontinuous replication of DNA -- The synthesis of DNA in discontinuous fragments on the lagging strand of the replication fork. The fragments, known as Okazaki fragments, are joined by DNA liga to form a continuous strand.
discontinuous variation -- Phenotypic data that fall into two or more distinct,
会计凭证怎么做non-overlapping class.
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discordance -- In twin studies, a situation where one twin express a trait but the other does not.
disjunction -- The paration of chromosomes at the anapha stage of cell division.
disruptive lection -- Simultaneous lection for phenotypic extremes in a population, usually resulting in the production of two phenotypically discontinuous strains.
dizygotic twins -- Twins produced from parate fertilization events; two ova fertilized independently. Also known as fraternal twins.
DNA -- See deoxyribonucleic acid.
DNA footprinting -- See footprinting.
DNA gyra -- One of the DNA topoisomeras that functions during DNA replication to reduce molecular tension caud by supercoiling. DNA gyra produces, then als, double-stranded breaks.
DNA liga -- An enzyme that forms a covalent bond between the 5' -end of one polynucleotide chain and the 3' -end of another polynucleotide chain. Also called polynucleotide-joining enzyme.
DNA polymera -- An enzyme that catalyzes the synthesis of DNA from deoxyribonucleotides and a template DNA molecule.
DNa -- Deoxyribonucleosida, an enzyme that degrades or breaks down DNA into fragments or constitutive nucleotides.
小桔灯论坛dominance -- The expression of a trait in the heterozygous condition.
dominant suppression -- A form of epistasis in which a dominant allele at one locus suppress the effect of a dominant allele at another locus, resulting in a 13:3 phenotypic ratio.
dosage compensation -- A genetic mechanism that regulates the levels of gene products at certain loci on the X chromosome in mammals such that males and females have equal amounts of a gene product. In mammals, this is accomplished by random inactivation of one X chromosome.
double-crossover -- Two parate events of chromosome breakage and exchange occurring within the same tetrad.
double helix -- The model for DNA structure propod by James Watson and Francis Crick, involving two antiparallel, hydrogen-bonded polynucleotide chains wound into a right-handed helical configuration, with 10 ba pairs per full turn of the double helix. Often called B-DNA.
Duchenne muscular dystrophy -- An X-linked recessive genetic disorder caud by a mutation in the gene for dystrophin, a protein found in muscle cells.
duplication -- A chromosomal aberration in which a gment of the chromosome is repeated.
dyad -- The products of tetrad paration or disjunction at the first meiotic propha. Consists of two sister chromatids joined at the centromere.
dystrophin -- See Duchenne muscular dystrophy.
as long as you love me歌词Dark repair 暗修复：即切除修复(excision repair)。
Daughter chromosome 子染色体：后期(有丝分裂中)或后期II(减数分裂)产生的染色单体。degeneracy 简并：有的氨基酸有多个相应的密码子，这种现象称为简并。
deletion 缺失：染色体丢失了某一片段。
denaturation 变性：在一定条件下(高温或变性剂等)DNA双螺旋解链的过程。deoxyribonuclea 脱氧核糖核酸酶：一种催化DNA降解成核苷的酶，也叫DNa。Deoxyribonucleic acid 脱氧核糖核酸；由脱氧核糖核苷酸构成的高分子聚合物。互补的双链呈双螺旋形，它是绝大多数生物的遗传物质。
武汉美容学校romancedeoxyribo 脱氧核糖：DNA中5—碳糖，2’—位置上不是—OH基，故称脱氧核糖。determinant 决定簇：一种特殊的定位分子，它导致细胞发育采用了特定的命运。determination 决定：细胞对特殊命运定型的过程。
development 发育：从一个细胞变成生物个体的过程。
diakinesis 终变期：减数分裂中的一个阶段，也叫浓缩期。细胞处于前期末，即将进人分裂期，可观察到“X”形、“O”形染色体。
Dicentric chromosome 双着丝粒染色体：带有两个着丝粒的染色体，常为不平衡易位所造成，在细胞分裂时可形成染色体桥，断裂后产生进一步的重复和缺失。dideoxynucletide 双脱氧核苷酸：一种修饰的核苷酸，其脱氧核糖的2’—OH和3’—OH都因脱氧而变成2’—H和3’—H。这样下一个核苷酸不能通过5’磷酸与之形成3’，5’—磷酸二酯键，使DNA链的延伸终止在这个双脱氧核苷酸处。
Dideoxy (sanger) quencing Sanger 双脱氧测序法：一种测序方法，Sanger在加减法原理的基础上，利用双脱氧核苷酸可终止DNA链的延伸的原理来测序。
differentiation 分化：在发育中细胞的形态和生理功能发生了改变，最终产生了不同的组织和器官。
Dihybrid cross 双因子杂种杂交：某些类型的双因子杂种之间的杂交。双因子杂种是指个体在两个不同的基因座位上两对等位基因是杂合的。
dimorphism 双态现象：一个群体中只有两种不同类型的多态现象。
diploid 二倍体：一个细胞或个体的每个细胞中具有两套染色体。
diplonema 双线期：减数分裂中前期I的第四阶段。
Directed mutagenesis 定向诱变：改变克隆基因的特定部分，再把被修饰的基因重新导入有机体中。
Directional lection 定向选择：以一个恒定的方向进行选择，使等位基因的频率发生改变，不是使一个等位基因固定就是使其淘汰。
Discontinuous DNA replication DNA不连续复制：在半不连续复制发现以前，人们认为DNA 的前导链和后滞链的合成都是不连续的，即先合成短的DNA片段，然后连接成长片段。
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Dispersive replication 散乱复制：DNA合成的散乱模型，认为在子代DNA分子中，亲代片段和新合成的片段随机交替排列。
DNA clone DNA克隆：将特定DNA片段插入载体分子中，然后转化细菌，使重组载体形成很多拷贝。
DNA fingerprint DNA指纹：用限制酶来切VNTRs(可变数同向重复序列)，然后用VNTR 特异探针和酶切片段进行Southern杂交，经放射自显影产生大量的杂交带，不同人的VNTRs的位置不同，因此杂交带的位置也不同，故称DNA指纹。
DNA helica DNA解旋酶：在正．coli复制中，催化DNA双链解旋的一种酶，是rep基因的产物。
DNAliga DNA连接酶：在DNA复制和修复时，催化DNA分子游离单链末端之间形成共价键的一种酶。
DNA polymera DNA聚合酶：一种催化DNA合成的酶。
DNA polymera I DNA聚合酶I：正．coli中催化DNA合成的酶，原称Kornberg酶，它主要负责损伤的修复和冈崎片段之间隙的填补。
DNA prima DNA引发酶：在C-4和~X174噬菌体DNA合成中，此酶催化合成短的核苷酸引物。
Docking protein 停泊蛋白或船坞蛋白，停靠蛋白：粗面内质网(ER)的膜结合蛋白，在蛋白越膜前，结合在核糖体新生肽的信号识别蛋白(SRP)可识别ER膜上的停泊蛋白使具有信号肽的多肽和ER结合。
Dominance variance(V o) 显性方差：在遗传方差中由基因的显性效应所产生的部分。dominant 显性：无论在纯合还是杂合时可得到表达的等位基因或表型。
Dominant lethal allele 显性等位致死：一个等位基因无论在纯合还是杂合时都产生致死效应。
Dosage compensation 剂量补偿：在性别决定中XY型的动物的雌体和雄体的X染色体的数目虽然不同，但它们具有一种机制使x连锁基因的产物数量相等，如哺乳动物用雌性动物一条X染色体失活的方式来达到剂量补偿。
Double crossover 双交换：在减数分裂时染色体的两个标记之间发生了两次交换。Double helix 双螺旋：1953年，由Watson和Crick提出的DNA分子结构模型，两条反向平行的DNA单链彼此由氢键A—T，G—C互补连接，整个分子成双螺旋状。Double infection 双感染或并感染：用两种不同的噬菌体
同时感染细菌。
Down syndrome 唐氏综合征：一种人类的染色体病，患者的第21号染色体多出一条，故称21—三体病，患者发育迟缓，智力低下。
drift 漂变：即遗传漂变，由于群体太小使基因频率发生随机波动，有时会丢失某基因而固定另一基因。
Duchenne muscular dystrophy 杜兴氏肌营养不良：又称假性肥大型营养不良或进行性营养不良，是人类中一种X隐性伴性遗传疾病，患者肌无力，几岁时发病，十几岁夭折。duplication 重复：染色体结构变异的一种，即染色体组多了一段染色体片段。
dyad 二联体：在第一次减数分裂时由着丝粒连接的一对姊妹染色单体。
