Birgid Schlindwein's
Hypermedia Glossary Of Genetic Terms
Search Results
Birgid Schlindwein'sHypermedia Glossary Of Genetic TermsSearch Results |
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| Sequence tagged site (STS) | Short (200 to 500 base pairs) sequence of genomic DNA that has a single occurrence in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful for localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome. Expressed sequence tag (EST) is STS derived from cDNA. |
| 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. |
| Polymerase chain reaction (PCR) | A method, developed by Kary Banks Mullis 1983, for amplifying a DNA base sequence using a heat-stable polymerase and two 20-base primers, one complementary to the (+)-strand at one end of the sequence to be amplified and the other complementary to the (-)-strand at the other end. Because the newly synthesized DNA strands can subsequently serve as additional templates for the same primer sequences, successive rounds of primer annealing, strand elongation, and dissociation produce rapid and highly specific amplification of the desired sequence. PCR also can be used to detect the existence of the defined sequence in a DNA sample (see DNA amplification fingerprinting. Several variations have been developed for specific needs. May be combined with reverse transcription of mRNA to cDNA to amplify an mRNA so called RT-PCR. |
| 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. |
| 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. |