Glossary – M

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M

major histocompatibility complex (MHC)
MHC molecules are proteins localized on the cell surface of all nucleated cells. They play an important role in the immune system because they bind to fragments of proteins that result from the normal protein turnover of a living cell and present them to T cells. T cells can recognize the MHC-presented peptides, and whenever these peptides belong to proteins of pathogens, the T cells are activated and induce an immune response.

metastasis
A metastasis is daughter tumor formed by cells derived from the primary tumor. It is a sign of malignancy when the primary tumor acquires the ability to spread to other sites of the body via the bloodstream or the lymphatic system.

messenger RNA (mRNA)
mRNA carries the message of how to build a protein from the DNA to the protein building complexes of the cell, the ribosomes. mRNA is derived from DNA by the process of transcription. As mRNA codes directly for proteins, it can be transferred into cells to induce the expression of foreign proteins.

MHC
See major histocompatibility complex

microarray
Microarrays are commonly known as DNA chips: A huge number of short DNA fragments that all differ in their sequence (oligos) are spotted onto a chip. Complementary DNA (cDNA) isolated from samples interact sequence specifically with a subset of the detectable oligos. Microarrays are used to simultaneously measure the expression levels of a large number of genes.

micro RNA (miRNA)
miRNA are so-called small non-coding RNA, i.e. RNA that does not code for proteins. miRNA has important regulatory functions; it inhibits the expression of proteins by inhibiting the translation of or degrading mRNA.

microinjection
The process of transferring a substance (e.g. DNA) into a single cell with a micropipette. This method is often used to generate transgenic mice.

mRNA
See messenger RNA

miRNA
see micro RNA

mitogen
A substance that is able to initiate cell divisions (mitosis) in cells.