【正文】 r ends.bp is an abbreviation for base pairs。 a diploid cell has two copies of each autosome.Blymphocytes (or B cells) are the cells responsible for synthesizing antibodies.Backcross is another (earlier) term for a testcross.Back mutation reverses the effect of a mutation that hand inactivated a gene。 it inhibhits transcription by certain eukaryotic RNA polymerases, especially RNA polymerase II.Amber codon is the nucleotide triplet UAG, one of three codons that cause termination of protein synthesis.Amber mutaion describes any change in DNA that creates an amber codon at a site previously occupied by a codon representing an amino acid in a protein.Amber suppressors are mutant genes that code for tRNAs whose anticodons have been altered so that they can respond to UAG codons as well as or instead of to their previous codons.AminoacyltRNA is transfer RNA carrying an amino acid。 the covalent linkage is between the NH2 group of the amino acid and either the 3’or2’OH group of the terminal base of the tRNA.AminoacyltRNA synthetases are enzymes responsible for covalently linking amino acids to the 2’ or 3’OH position of tRNA.Amphipathic structures have two surfaces, one hydrophilic and one hydrophobic. Lipids are amphipathic。 thus it restores wild type.Bacteriophages are viruses that infect bacteria。 distance along DNA is measured in bp.Branch migration describes the ability of a DNA strand partially paired with its plement in a duplex to extend its pairing by displacing the resident strand with which it is homologous.Breackage and reunion describes the mode of genetic rebination, in which two DNA duplex molecules are broken at corresponding points and then rejoined crosswise (involving formation of a length of heteroduplex DNA around the site of joining).Buoyant desity measures the ability of a substance to float in some standard fluid, for example, CsCl.C banding is a technique for generating stained regions around centromeres.C genes code for the constant regions of immunoglobulin protein chains.C value is the total amount of DNA in a haploid genome.CAAT box is part of a conserved sequence located upstream of the startpoints of eukaryotic transcription units。 neither is dominant over the other.Coevolution —see concerted evolution.Cognate tRNAs are those recognized by a particular aminoacytRNA synthetase.Coointegrate structure is produced by fusion of two replicons, one originally possessing a transposon, the other lacking it。 its structure appears similar to that of the nucleosome itself.Corepressor is a small molecule that triggers repression of transcription by binding to a regulator protein.Cosmids are plasmids into which phage lambda cos sites have been inserted。 its binding activates the CAP, a postive regulator of prokaryotic transcription.Cyclins are proteins that accumulate continuously throughout the cell cycle and are then destroyed by proteolysis during mitosis. (see also MPF).Cytokinesis is the final process involved in separation and movement apart of daughter cells at the end of mitosis.Cytological hybridization—see in situ hybridization.Cytoplasm describes the material between the plasma membrane and the nucleus.Cytoplasmic inheritance is a property of genes located in mitochondria or chloroplasts (or possibly other extranuclear organelles).Cytoplasmic protein synthesis is the ranslation of mRNAs representing nuclear genes。 they aer not necessarily adjacent.Discontinuous replication refers to the synthesis of DNA in short (Okazaki) fragments that are later joined into a continuous strand.Disjunction describes the movement of members of a chromosome pair to opposite poles during cell division. At mitosis and the second meiotic division, disjunction applies to sister chromatids。 for example, in a transgenic animal.Elongation factors (EF in prokaryotes, eEF in eukaryotes) are proteins that associate with ribosomes cyclically, during addition of each amino acid to the polypeptide chain.End labeling describes the addition of a radioactively labeled group to one end (5’ or 3’) of a DNA strand.Endproduct inhibition describes the ability of a product of a metabolic pathway to inhibit the activity of an enzyme that catalyzes an early step in the pathway.Endocytosis is a process by which proteins at the surface of the cell are internalized, being transported into the cell within membranous vesicles.Endocytic vesicles are membranous particles that transport proteins through endocytosis。 it indicates the ability of lipids to move laterally within their particular monolayer.Focus formation describes the ability of transformed eukaryotic cells to grow in dense clusters, piled up on one another.Focus forming unit (ffu) is a quantitative measure of forcus formation.Foldback DNA consists of inverted repeats that have renatured by intrastrand reassociation of denatured DNA.Foot printing is a technique for identifying the site on DNA bound by some protein by virtue of the protection of bonds in this region against attack by nucleases.Forward mutations inatctivate a wildtype gene.Founder effect refers to the presence in a population of many individuals all with the same chromosome (or region of a chromosome) derived from a single ancestor.Frameshift mutations arise by deletions or insertions that are not a multiple of 3bp。 involed in glycosylating proteins and sorting them for transport to different cellular locations.G proteins are guanine nucleotidebinding trimeric proteins that reside in the plasma membrane. When bound by GDP the trimer remains intact and is inert. When the GDP bound to。 it includes regions preceding and following the coding region (leader and trailer) as well as intervening sequences (introns) between individual coding segments (exons).Gene conversion is the alteration of one strand of a heteroduplex DNA to make it plementary with the other strand at any position(s) where