Birgid Schlindwein's
Hypermedia Glossary Of Genetic Terms
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Birgid Schlindwein'sHypermedia Glossary Of Genetic TermsSearch Results |
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| Physical map | A map of the locations of identifiable landmarks on DNA (e.g., restriction enzyme cutting sites, genes), regardless of inheritance. Landmarks include restriction endonuclease recognition sites, DNA sequence and chromosomal bands. Distance is measured in base pairs. For the human genome, the lowest-resolution physical map is the banding patterns on the 24 different chromosomes; the highest-resolution map would be the complete nucleotide sequence of the chromosomes. |
| Deoxyribonucleic acid (DNA) | The molecule that encodes genetic information. DNA is a double-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 and C; thus the base sequence of each single strand can be deduced from that of its partner. |
| Restriction enzyme cutting site | A specific nucleotide sequence of DNA at which a particular restriction enzyme cuts the DNA. Some sites occur frequently in DNA (e.g., every several hundred base pairs), others much less frequently (rare-cutter; e.g., every 10,000 base pairs). |
| 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. |
| Inheritance | Trait which is derived by an heir from an ancestor; transmission and reception by animal or plant generation. Trait acquired via biological heredity that passes from parent to offspring. |
| Restriction enzyme | A bacterially derived protein that recognizes specific, short nucleotide sequences and cuts DNA at those sites. Bacteria contain over 400 such enzymes that recognize and cut over 100 different DNA sequences. See restriction enzyme cutting site and endonuclease. |
| 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. |
| Base pair (bp) | Two nitrogenous (purine or pyrimidine) bases (adenine and thymine or guanine and cytosine) held together by weak hydrogen bonds. Two strands of DNA are held together in the shape of a double helix by the bonds between base pairs. The number of base pairs is often used as a measure of length of a DNA segment, eg 500 bp. |
| Genome | All the genetic material in the chromosomes of a particular organism; its size is generally given as its total number of base pairs. |
| 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. |
| Nucleotide | A subunit of DNA or RNA consisting of a nitrogenous base (purine in adenine and guanine, pyrimidine in thymine, or cytosine for DNA and uracil cytosine for RNA), a phosphate molecule, and a sugar molecule (deoxyribose in DNA and ribose in RNA). Depending on the sugar the nucleotides are called deoxyribonucleotides or ribonucleotides. Thousands of nucleotides are linked to form a DNA or RNA molecule. See also base pair. |