分子生物学名词解释(英文).doc

Structure and Function of Nucleic Acid1The primary structure of nucleic acid is the sequence of nucleoside monophosphates from 5 end to 3 end in nucleic acid . (usually written as the sequence of bases).2DNA denaturation：A DNA has lost its native conformation and double strand DNA is separated to single strand DNA by exposed to a destabilizing factor such as heat, acid, alkali,urea or amide. (when high temperature is used to denature DNA, the DNA is said to be melted).3Tm：is melting temperature at which half (50%) of DNA molecules are denatured.4. Annealing ：The process of renaturation of heat denatured DNA by slowly cooling is called annealing.5Hyperchromic effect: the absorbance at 260nm of a DNA solution increases when the double helix is melted into single strands.6Hybridization: when heterogeneous DNA or RNA are put together, they will become to heteroduplex via the base-pairing rules during renaturation if they are complementary in parts (not complete). This is called molecular hybridization.Replication1The Central Dogma：It described that the flow of genetic information is from DNA to RNA and then to protein. According to the central dogma of molecular biology, DNA directs the synthesis of RNA, and RNA then directs the synthesis of proteins. 2Semiconservative replication：* The two parental strands separate and that each then serves as a template;* 4 kinds of dNTP as the stock;* Catalyzed by DNA polymerase;* Follow the usual base-pairing rules of A with T and G with C;* Each daughter duplex has one parental strand and one newly synthesized strand.3Okazaki fragments ：The Short segments of DNA (10002000 bases in bacteria, 150-200 bases in eukaryotes) formed in the discontinuous lagging strand synthesis of DNA and are rapidly joined by DNA ligase to form a continuous DNA strand.4Replicon： A unit of DNA that is replicated from one replication origin.5Primosome：The protein complex containing DnaB, DnaC, primase (DnaG), DNA oriC sequence and other factors that initiates synthesis of DNA. DNA synthesis proceeds in a 53 direction and is semidiscontinuous. One of the new DNA strands is synthesized continuously and the other discontinuously in short pieces： 6Leading strand ： The strand that is continuously synthesized (in the same direction as replication fork movement).7Lagging strand ： The strand that is synthesized discontinuously in short pieces (Okazaki fragments) in a direction opposite to the direction of replication fork movement. The Okazaki fragments are then spliced together by DNA ligase.8Telomere：Specialized structure at the end of a linear eukaryotic chromosome, which consists of tandem repeats of a short T,G-rich sequence on the 3 ending strand and its complementary sequence on the 5 ending strand, allows replication of 5 ends of the DNA without loss of genetic information and maintains the stability of eukaryotic chromosome.9Telomerase： An RNA-containing reverse transcriptase that using the RNA as a template, adds nucleotides to the 3 ending strand and thus prevents progressive shortening of eukaryotic linear DNA molecules during replication. Human telomerase contains three parts: Human telomerase RNA, hTR Human telomerase associated protein 1, hTP1 Human telomerase reverse transcriptase, hTRT10Reverse Transcription：Synthesis of a double-strand DNA from an RNA template.11Reverse transcriptase：A DNA polymerase that uses RNA as its template. RNA-dependent DNA polymerase RNase DNA-dependent DNA polymeraseGene Recombination and Genetic Engineering1. DNA Cloning: To clone a piece of DNA, DNA is cut into fragments using restriction enzymes. The fragments are pasted into vectors that have been cut by restriction enzyme to form recombinant DNA. The recombinant DNA are needed to transfer and replicate DNA in a host cell.This serial process and related technique are called DNA cloning, also called gene cloning.2. Genomic DNA library:The collection of bacteria clones that contain all the DNA in the organisms genome on vector of plasmids or bacteriophage.3. -complementation: some plasmid vectors (eg,pUC19) carry lacZ gene, whose product fragment is the N-terminal of the -galactosidase. Whereas, the mutant E.coli strain only synthesize the fragment, which is the C-terminal of the enzyme. Either or fragment alone is nonfunctional. When the vector containing lacZ is introduced into mutant E.coli, both theand fragments are present. So there is an interaction and a functionally intact -galactosidase can form. This interaction is called - complementation. Regulation of Gene Expression1. Housekeeping gene: It is the genes coding for proteins that are needed for basic life processes in all kinds of cells(such as enzymes for citric acid cycle). 2. Operon: consists of more than 2 coding sequences, promoter, operator and other regulatory sequences clustered in the genome.3. Promoter: It is the specific DNA sequence binding to RNA-pol to initiate transcription.4. Enhancer: consisting of several functional elements, apart from transcriptional initiation site, enhancing the activity of promoter, determining the stage and spatial specificity, functioning in different direction and distance on upstream or downstream。5. cis-acting element: It is the specific DNA sequences regulating geneexpression (control gene expression only on the same chromosome).It is the site binding RNA-pol and transcription factors.6. Trans-acting factor: They are the protein factors that can interact withthe cis-acting element of other gene, and control the transcription of other gene. Cell Communication and Signal Transduction1G-protein: GTP-binding protein, a membrane-associated protein, consists of , , and subunits, the subunit of the G-protein binds GTP or GDP, when the subunit has GTP bound, the -subunit leave, and the G-protein are active which can activate AC then induce biological effect.2Secondary messenger: are small signaling molecules that are generated in the cell in response to extracellular signals. They can activate many other downstream components. The most important second messengers are: Ca2+, cAMP, cGMP, DAG, IP3, Cer, etc.3Calmodulin: is a small cytosol protein, single polypeptide, 1 CaM can bind 4 Ca2+, binding of Ca2+ causes CaM to undergo a conformational change, then Ca2+-CaM can regulate some protein kinase including Ca2+/calmodulin-dependent protein kinase. 4Ras protein: 1 polypeptide, coding by ras gene, 21kD (P21 protein or small G protein), GTP-binding membrane protein, function as Gof G protein, alternates between an active on state with a bound GTP and an inactive off state with a bound GDP. Ras protein has important functions in cell signal transduction and mutant Ras plays important roles in tumorigenesis.Oncogene and Tumor suppressor gene1Oncogenes： genes whose products have the ability to transform eukaryotic cells in culture or to induce cancer in animals, including virus oncogene（v-onc）and cellular oncogene (c-onc). Most oncogene are mutant forms of normal genes （ proto- onc） involved in the control of cell growth or division.2Proto-oncogenes are the normal counterparts in the eukaryotic genome to the oncogenes carried by some retroviruses. They are often directly involved in growth regulation of normal cells.3Tumor suppressor genes(anti-oncogene)：genes that have a negative, suppressing effect on tumor creation and thus help to prevent formation of tumors. They function cooperatively with pro-oncogenes to regulate cell growth、proliferation and differentiation. Mutant anti-oncogenes also can induce tumorigenesis.4Apoptosis: When cells receive some extracellular signals or are effected with pathological stimulus, they can initiate a series of gene expression and kill themselves. This kind of death is positive and have important significance in keeping balance of internal environment、development、etc.Molecular biology techniques commonly used1. Southern blotting : Genomic DNA (from tissues or cells) are cut by RE, separated by gel electrophoresis and denatured in solution, then transferred to a nitrocellulose membrane for detecting specific DNA sequence by hybridization to a labeled probe. It can be used to quantitative and qualitative analyze genomic DNA, or analyze the recombinant plasmid and bacteriophage(screening DNA library) 2. Northern blotting: RNA samples (from tissues or cells) are cut by RE, separated by gel electrophoresis and denatured in solution, then transferred to a nitrocellulose membrane for detecting specific sequence by hybridization to a labeled probe. It can be used to detect the level of specific mRNA in some tissues (cells) and to compare the level of same gene expression in different tissues (cells) or at different development period.3. Western blotting