Marker

- Any genetic element ( locus, allele, DNA sequence or chromosome feature) which can be readily detected by phenotype, cytological or molecular techniques, and used to follow a chromosome or chromosomal segment during genetic analysis.
Definition from:
http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-M/marker.html

- 1. A genetic marker is a gene that has been mapped and can be identified.
- 2. A molecular weight marker is a DNA fragment of known size used as a comparison standard in estimating the size of a DNA fragment of unknown size
Definition from:
Genelex

- 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
Definition from:
Hypermedia Glossary Of Genetic Terms

- A gene of known location on a chromosome and phenotype that is used as a point of reference in the mapping of other loci.
Definition from:
http://www.cstl.nist.gov/div831/strbase/glossary.htm

Magnesium

- Magnesium is a required cofactor for thermostable DNA polymerases, and magnesium concentration is a crucial factor that can affect the success of the amplification. ...
Definition from:
http://www.promega.com/paguide/chap1.htm

- DNA polymerase requires magnesium for activity. Magnesium is usually supplied to a PCR amplification in the form of magnesium chloride.
PCR Optimization Student Manual
Frank H. Stephenson and Maria C. Abilock

Megabase ( Mb )

- Unit of DNA or RNA sequence equal to one million nucleotides
Definition from:
Mouse Genome Informatics

Melting of DNA

- Denaturation of duplex DNA by heat or increased pH leading to strand separation.
Definition from:
http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-M/melting_of_DNA.html

Microgram ( µg )

- A measurement of weight. One microgram is equal to one thousandth of a milligram.

Microsatellite

- Microsatellite Marker. A short (up to several hundred base pairs) segment of DNA that consists of multiple tandem repeats of a two or three base-pair sequence. Microsatellites expand and contract (that is, add or remove repeat units) with a frequency much higher than other types of mutations, making them useful as polymorphic markers in closely related mouse strains.
Definition from:
Mouse Genome Informatics

- Microsatellites are defined as short patterned non-coding regions containing specific genetic sequences that are repeated one right after the other (in direct sequence) within the genome of an organism. The repeated sequence in a microsatellite consists of two, three or four nucleotides (di-, tri-, or tetra-nucleotide repeats respectively) and can be repeated many times (upwards of 100).
Definition from:
ISCID

- Repetitive stretches of short sequences of DNA used as genetic markers to track inheritance in families. They are short sequences of nucleotides (example: ATCG) which are repeated over and over again a number of times in tandem. Changes sometimes do occur, however, and the number of repeats may increase or decrease.
Definition from:
Genetics/DNA Glossary

- A type of repetitive DNA based on very short repeats such as dinucleotides, trinucleotides or tetranucleotides.
Definition from:
http://www.igd.cornell.edu/MolecularMarkers/Glossary.pdf

Molecular beacons

- Real Time Amplification System.They are hairpin-shaped molecules that contain a stem-loop structure, a fluorophore and a quencher (Dabcyl). The stem sequence keeps the fluorophore and the quencher in close proximity so that any photons emitted by the fluorophore are absorbed by the quencher. The loop sequence is complementary with the target. When the probe finds its target, the loop opens and hybridises to the target. This removes the fluorophore from the vicinity of the quencher, allowing the fluorescence to appear and be measured. Molecular Beacons are designed to remain intact during the amplification reaction, and must rebind to target in every cycle for signal measurement. Molecular Beacons form a stem-loop structure when free in solution. Thus, the close proximity of the fluor and quench molecules prevents the probe from fluorescing. When a Molecular Beacon hybridises to a target, the fluorescent dye and quencher are separated, FRET does not occur, and the fluorescent dye emits light upon irradiation. Molecular Beacons can be used for multiplex assays by using spectrally separated fluor/quencher moieties on each probe.
Definition from:
http://www.biotools.net/eng/tecnica/t33.htm

- A molecular beacon is a single-strand oligonucleotide hybridization probe forming a stem-and-loop structure. The loop in this sequence is complementary to a target sequence on a larger nucleotide structure (DNA or RNA) and thus works as a probe, and the stem is formed by annealing the complementary arm sequences on either side of the loop. Molecular beacons do not fluorescence when free in solution, but when they are bonded to a target sequence, they undergo changes, primarily a separation of the stem sequences, that cause them to fluoresce brightly. This means that if the probe does not find a target, the molecular beacon will not glow.
Definition from:
ISCID

Messenger RNA (mRNA)

- An RNA molecule transcribed from the DNA of a gene, and from which a protein is translated by the action of ribosomes. The basic function of the nucleotide sequence of mRNA is to determine the amino acid sequence in proteins.
Definition from:
http://www.biochem.northwestern.edu/holmgren/Glossary/Definitions/Def-M/messenger_RNA.html

- RNA that serves as a template for protein synthesis or for synthesis of cDNA.
Definition from:
Hypermedia Glossary Of Genetic Terms

Mitochondrial DNA ( mtDNA )

- The genetic material found in mitochondria, the organelles that generate energy for the cell. Not inherited in the same fashion as nucleic DNA
Definition from:
Genome Glossary
 

Multiplex PCR

- Multiplex PCR is the term used when more than one pair of primers is used in a PCR. The goal of multiplex PCR is to amplify several segments of target DNA simultaneously and thereby to conserve template DNA, save time, and minimize expense. It is a PCR strategy that enables the amplification of multiple DNA targets in one run.
Definition from:
http://viroligo.okstate.edu/enterdata/PCRs.htm

- Multiplex PCR is simply a PCR reaction where two or more targets are detected in the same reaction. ...
Definition from:
http://www.aphis.usda.gov/ppq/ispm/pramorum/pdf_files/diagnostics.pdf

Mutation

- The term which De Vries introduced into biological literature for an abrupt change of genotype which is inherited. Any permanent and heritable change in DNA sequence. Types of mutations include point mutations, deletions, insertions, and changes in number and structure of chromosomes.
Definition from:
Hypermedia Glossary Of Genetic Terms

- 1.The process through which genes undergo a structural change.
- 2.Any permanent change in DNA, i.e., in its nucleotide sequence. Examples include chromosome rearrangements and point mutations.
Definition from:
Mouse Genome Informatics

- An alteration of the genetic material of a cell that may be caused either by spontaneous changes or by external forces (such as radiation). Mutations that occur in the gametes (sex cells) of an organism are heritable. Mutations are thought to be the primary mechanism of variation upon which natural selection operates
Definition from:
ISCID

- Any inheritable changes in the DNA sequence that occurs during reproduction or cell division.
Definition from:
Genelex

- A permanent structural alteration in DNA. In most cases, DNA changes either have no effect or cause harm, but occasionally a mutation can improve an organism's chance of surviving and passing the beneficial change on to its descendants.
Definition from:
Genetics/DNA Glossary