Genome Project - Primer on molecular genetics - 1992 (522926), страница 7
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All human genes will eventually be found, andaccurate diagnostics will be developed for most inherited diseases. In addition, animalmodels for human disease research will be more easily developed, facilitating the understanding of gene function in health and disease.Researchers have already identified single genes associated with a number of diseases,such as cystic fibrosis, Duchenne muscular dystrophy, myotonic dystrophy, neurofibromatosis, and retinoblastoma. As research progresses, investigators will also uncover themechanisms for diseases caused by several genes or by a gene interacting with environmental factors.
Genetic susceptibilities have been implicated in many major disabling andfatal diseases including heart disease, stroke, diabetes, and several kinds of cancer. Theidentification of these genes and their proteins will pave the way to more-effectivetherapies and preventive measures. Investigators determining the underlying biology ofgenome organization and gene regulation will also begin to understand how humansdevelop from single cells to adults, why this process sometimes goes awry, and whatchanges take place as people age.New technologies developed for genome research will also find myriad applications inindustry, as well as in projects to map (and ultimately improve) the genomes of economically important farm animals and crops.While human genome research itself does not pose any new ethical dilemmas, the use ofdata arising from these studies presents challenges that need to be addressed before thedata accumulate significantly.
To assist in policy development, the ethics component ofthe Human Genome Project is funding conferences and research projects to identify andconsider relevant issues, as well as activities to promote public awareness of these topics.3031GlossaryPortions of theglossary text weretaken directly ormodified from definitions in the U.S.Congress Office ofTechnology Assessment document:Mapping OurGenes—The GenomeProjects: How Big,How Fast? OTA-BA373, Washington,D.C.: U.S.
Government Printing Office,April 1988.Adenine (A): A nitrogenous base, one member of the base pair A-T (adenine-thymine).Alleles: Alternative forms of a genetic locus; a single allele for each locus is inheritedseparately from each parent (e.g., at a locus for eye color the allele might result in blue orbrown eyes).Amino acid: Any of a class of 20 molecules that are combined to form proteins in livingthings. The sequence of amino acids in a protein and hence protein function are determined by the genetic code.Amplification: An increase in the number of copies of a specific DNA fragment; can be invivo or in vitro. See cloning , polymerase chain reaction.Arrayed library: Individual primary recombinant clones (hosted in phage, cosmid, YAC,or other vector) that are placed in two-dimensional arrays in microtiter dishes.
Eachprimary clone can be identified by the identity of the plate and the clone location (row andcolumn) on that plate. Arrayed libraries of clones can be used for many applications,including screening for a specific gene or genomic region of interest as well as for physicalmapping. Information gathered on individual clones from various genetic linkage andphysical map analyses is entered into a relational database and used to construct physicaland genetic linkage maps simultaneously; clone identifiers serve to interrelate the multilevel maps.
Compare library, genomic library.Autoradiography: A technique that uses X-ray film to visualize radioactively labeledmolecules or fragments of molecules; used in analyzing length and number of DNAfragments after they are separated by gel electrophoresis.Autosome: A chromosome not involved in sex determination. The diploid human genomeconsists of 46 chromosomes, 22 pairs of autosomes, and 1 pair of sex chromosomes (theX and Y chromosomes).Bacteriophage: See phage.Base pair (bp): Two nitrogenous bases (adenine and thymine or guanine and cytosine )held together by weak bonds. Two strands of DNA are held together in the shape of adouble helix by the bonds between base pairs.Base sequence: The order of nucleotide bases in a DNA molecule.Base sequence analysis: A method, sometimes automated, for determining the basesequence.Biotechnology: A set of biological techniques developed through basic research and nowapplied to research and product development.
In particular, the use by industry of recombinant DNA, cell fusion, and new bioprocessing techniques.bp: See base pair.cDNA: See complementary DNA.32Centimorgan (cM): A unit of measure of recombination frequency. One centimorgan isequal to a 1% chance that a marker at one genetic locus will be separated from a markerat a second locus due to crossing over in a single generation. In human beings, 1 centimorgan is equivalent, on average, to 1 million base pairs.Centromere: A specialized chromosome region to which spindle fibers attach during celldivision.Chromosomes: The self-replicating genetic structures of cells containing the cellularDNA that bears in its nucleotide sequence the linear array of genes.
In prokaryotes,chromosomal DNA is circular, and the entire genome is carried on one chromosome.Eukaryotic genomes consist of a number of chromosomes whose DNA is associated withdifferent kinds of proteins.Clone bank: See genomic library.Clones: A group of cells derived from a single ancestor.Cloning: The process of asexually producing a group of cells (clones), all geneticallyidentical, from a single ancestor. In recombinant DNA technology, the use of DNA manipulation procedures to produce multiple copies of a single gene or segment of DNA isreferred to as cloning DNA.Cloning vector: DNA molecule originating from a virus, a plasmid, or the cell of a higherorganism into which another DNA fragment of appropriate size can be integrated withoutloss of the vector’s capacity for self-replication; vectors introduce foreign DNA into hostcells, where it can be reproduced in large quantities.
Examples are plasmids, cosmids,and yeast artificial chromosomes; vectors are often recombinant molecules containingDNA sequences from several sources.cM: See centimorgan.Code: See genetic code.Codon: See genetic code.Complementary DNA (cDNA): DNA that is synthesized from a messenger RNA template; the single-stranded form is often used as a probe in physical mapping.Complementary sequences: Nucleic acid base sequences that can form a doublestranded structure by matching base pairs; the complementary sequence to G-T-A-C isC-A-T-G.Conserved sequence: A base sequence in a DNA molecule (or an amino acid sequencein a protein) that has remained essentially unchanged throughout evolution.Contig map: A map depicting the relative order of a linked library of small overlappingclones representing a complete chromosomal segment.33GlossaryContigs: Groups of clones representing overlapping regions of a genome.Cosmid: Artificially constructed cloning vector containing the cos gene of phage lambda.Cosmids can be packaged in lambda phage particles for infection into E.
coli; this permitscloning of larger DNA fragments (up to 45 kb) than can be introduced into bacterial hostsin plasmid vectors.Crossing over: The breaking during meiosis of one maternal and one paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes. This process can result in an exchange of alleles between chromosomes. Compare recombination.Cytosine (C): A nitrogenous base, one member of the base pair G-C (guanine andcytosine).Deoxyribonucleotide: See nucleotide.Diploid: A full set of genetic material, consisting of paired chromosomes—one chromosome from each parental set. Most animal cells except the gametes have a diploid set ofchromosomes. The diploid human genome has 46 chromosomes. Compare haploid.DNA (deoxyribonucleic acid): The molecule that encodes genetic information.
DNA is adouble-stranded molecule held together by weak bonds between base pairs of nucleotides. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine(C), and thymine (T). In nature, base pairs form only between A and T and between G andC; thus the base sequence of each single strand can be deduced from that of its partner.DNA probes: See probe.DNA replication: The use of existing DNA as a template for the synthesis of new DNAstrands.
In humans and other eukaryotes, replication occurs in the cell nucleus.DNA sequence: The relative order of base pairs, whether in a fragment of DNA, a gene,a chromosome, or an entire genome. See base sequence analysis.Domain: A discrete portion of a protein with its own function. The combination of domainsin a single protein determines its overall function.Double helix: The shape that two linear strands of DNA assume when bonded together.E. coli: Common bacterium that has been studied intensively by geneticists because of itssmall genome size, normal lack of pathogenicity, and ease of growth in the laboratory.Electrophoresis: A method of separating large molecules (such as DNA fragments orproteins) from a mixture of similar molecules.
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