Birgid Schlindwein's
Hypermedia Glossary Of Genetic Terms
Search Results
Birgid Schlindwein'sHypermedia Glossary Of Genetic TermsSearch Results |
|
| see Disclaimer |
| Chromosome walking | Method involving hybridizing a primer of known sequence to a clone from an unordered genomic library and synthesizing a short complementary strand (called walking along a chromosome). The complementary strand is then sequenced and its end used as the next primer for further walking; in this way the adjacent, previously unknown, region is identified and sequenced. The chromosome is thus systematically sequenced from one end to the other. Because primers must be synthesized chemically, a disadvantage of this technique is the large number of different primers needed to walk a long distance. Chromosome walking is also used to locate specific genes by sequencing the chromosomal segments between markers that flank the gene of interest. Cf. chromosome jumping |
| Hybridization | The process of joining two complementary strands of DNA or one each of DNA and RNA to form a double-stranded molecule. One strand is often labeled and used as a probe to detect the presence of the second strand. Cf. hybrid. |
| Primer | Short preexisting single-stranded polynucleotide chain to which new deoxyribonucleotides can be added by DNA polymerase. It anneals to a nucleic acid template and promotes copying of the template starting from the primer site. |
| 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. |
| Clone bank | See genomic library. |
| Genomic library | A collection of clones made from a set of randomly generated overlapping DNA fragments representing the entire genome of an organism. Compare library, arrayed library. |
| Complementary DNA (cDNA) | DNA that is synthesized from a messenger RNA template that corresponds to expressed sequences of genomic DNA. The term complementary DNA also may refer to DNA that is complementary to a particular DNA sequence. The single-stranded form is often used as a probe in physical mapping. |
| Strand | It is customary in genetics to use strand for chromatid. It has therefore been used in that sense in some books, where it has also been used for one double-chain (that is, duplex) DNA molecule. Chain, but not strand, has been used for a single polynucleotide. |
| Chromosome | The term was proposed by Waldeyer (1888) for the individual threads within a cell nucleus (gk. chroma, colour; soma, body). The self-replicating genetic structures of cells containing the cellular DNA 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 with different kinds of proteins. |
| Sequencing | Determination of the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein. |
| Gene | The term coined by Johannsen (1909) for the fundamental physical and functional unit of heredity. The word gene was derived from De Vries' term pangen, itself a derivative of the word pangenesis which Darwin (1868) had coined. A gene is an ordered sequence of nucleotides located in a particular position (locus) on a particular chromosome that encodes a specific functional product (the gene product, i.e. a protein or RNA molecule). It includes regions involved in regulation of expression and regions that code for a specific functional product. See gene expression, allele. |
| Marker | An identifiable physical location on a chromosome (e.g., restriction enzyme cutting site, gene, minisatellite, microsatellite) whose inheritance can be monitored. Markers can be expressed regions of DNA (genes) or some segment of DNA with no known coding function but whose pattern of inheritance can be determined. See RFLP, restriction fragment length polymorphism. |
| Flanking region | The DNA sequence extending on either side of a specific gene or locus |
| Chromosome jumping | A technique of isolating clones from a genomic library that are not contiguous by skipping a region between known points on the chromosome. Done usually to bypass regions that are difficult or impossible to walk through or regions known not to be of interest. |