Amplification (genetics)

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Amplification refers to the reproduction of DNA sections. In genetics, amplification describes a naturally occurring increase ( replication ) of certain DNA sequences . It is used in molecular biology in vitro to multiply DNA. The reproduction of the entire genome by polyploidization is not an amplification in the strict sense, since large amounts of DNA are also reproduced without any recognizable relevance.

properties

The naturally occurring amplification of DNA segments is a form of mutation and presumably serves to accelerate evolution through accordion-like expansions and contractions of DNA segments in the genome . This can e.g. B. lead to an accelerated development of resistance , for example against antibiotics or insecticides .

Forms of natural amplification

The targeted reproduction of DNA is also a natural process. It is used to increase the gene dose of individual genes , usually through gene duplication, if necessary. One has with several living beings, z. B. found in the yellow beetle ( Dytiscus marginalis ) or the clawed frog ( Xenopus laevis ) that they can amplify ribosomal DNA extrachromosomally. This happens especially with egg cells , since there the need for ribosomes is greatly increased. The amplification is carried out by cutting out the rDNA and making it circular. The rDNA rings are then increased by rolling circle replication and thus compensate for the deficiency. Another example of natural amplification is provided by the genes for the egg envelope ( chorion ) in the follicle cells of Drosophila melanogaster . In front of the genes there is a unidirectional origin of replication (ori). This has the effect that only the genes are selectively replicated, while other genomic areas remain in the old number. The replication starts with the genes several times, so that it looks like an onion skin structure under the electron microscope , which is why it is also called onion skin replication . The chorionic genes are increased sixteen-fold in order to provide enough proteins for the rapid egg growth.

Health effects

In some oncogenes , amplifications occur in the course of oncogenesis , e.g. B. at HER2 / new . Such pathological amplification is understood “as a reaction” of some oncogenes to cytostatics . In cancer therapy , cytostatic agents are often used that prevent the production of nucleobases or their starting materials. The cancer cells occasionally react to this by amplifying those gene regions whose gene products are inhibited or blocked by the cytostatics. Amplifications are predominantly intrachromosomal. Their formation can be seen in the light microscope as homogeneous staining regions , as homogeneous chromosome extensions , or extrachromosomally as so-called double minutes .

Amplification as a Technique

The replication of DNA is also called amplification, the starting sequence is called amplicon and the product is called amplificate. The most important technique of amplification is probably the targeted replication of DNA by polymerase chain reaction . In addition, isothermal methods such as multidisplacement amplification , isothermal assembly or recombinase polymerase amplification are used.

Individual evidence

  1. ↑ M. Debatisse, B. Malfoy: Gene amplification mechanisms. In: Advances in Experimental Medicine and Biology . Volume 570, 2005, pp. 343-361, ISSN  0065-2598 . doi : 10.1007 / 1-4020-3764-3_12 . PMID 18727507 .
  2. ↑ KT Elliott, LE Cuff, EL Neidle: Copy number change: evolving views on gene amplification. In: Future microbiology. Volume 8, Number 7, July 2013, pp. 887-899, ISSN  1746-0921 . doi : 10.2217 / fmb.13.53 . PMID 23841635 .
  3. ↑ L. Sandegren, DI Andersson: Bacterial gene amplification: implications for the evolution of antibiotic resistance. In: Nature reviews. Microbiology. Volume 7, Number 8, August 2009, pp. 578-588, ISSN  1740-1534 . doi : 10.1038 / nrmicro2174 . PMID 19609259 .
  4. ↑ C. Bass, LM Field: Gene amplification and insecticide resistance. In: Pest management science. Volume 67, Number 8, August 2011, pp. 886-890, ISSN  1526-4998 . doi : 10.1002 / ps.2189 . PMID 21538802 .
  5. ↑ M. Yan, BA Parker, R. Schwab, R. Kurzrock: HER2 aberrations in cancer: Implications for therapy. In: Cancer treatment reviews. [electronic publication before printing] March 2014, ISSN  1532-1967 . doi : 10.1016 / j.ctrv.2014.02.008 . PMID 24656976 .
  6. ↑ C. Zhang, J. Xu, W. Ma, W. Zheng: PCR microfluidic devices for DNA amplification. In: Biotechnology Advances . Volume 24, Number 3, 2006 May-Jun, pp. 243-284, ISSN  0734-9750 . doi : 10.1016 / j.biotechadv.2005.10.002 . PMID 16326063 .