Evolution of the major histocompatibility complex: birth-and-death evolution model

Bašić, Mila (2011) Evolution of the major histocompatibility complex: birth-and-death evolution model. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

The MHC molecules are important part od immunity. Their function is presenting peptide fragments of antigens to T-cells. Genes coding for the MHC are a part of the multigene family. This means that they are of the same origin and have a similar DNA sequence. MHC region is divided in three regions, one that codes for MHC-I, second that codes for MHC-II and the third one, MHC-III, which is positioned between the first two regions. Evolution of multigene families, like the rRNA genes, histone genes, immunoglobulin gene family, MHC gene family, has been studied for a long time, consequently different models explaining their evolution appeared. For a certain time, it was believed that the evolution of the MHC followed a pattern called concerted evolution. According to this model, the cause of evolution are spontanious mutations arising in a repeat unit and are then spread rapidly throughout the multigene family by unequal crossing-over or gene conversion. Although these occurrences are not questionable, there is no evidence that they are occuring often enough or even important enough to have a role in gene evolution of the entire multigene family. The MHC genes apparently evolved following birth-and-death evolution, where new genes are created by gene duplication. While some genes are maintained for a long time, others are deleted or become nonfunctional by deleterious mutations. Phylogenetic analyses, which are run thanks to an increasing number of identified DNA sequences in different species, confirm this model od evolution. Continued application of phylogenetic analysis produces not only a broader picture of evolution of these genes, but also evolution of multigene families in general.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Galov, Ana
Date: 2011
Number of Pages: 9
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 24 Oct 2014 09:51
Last Modified: 24 Oct 2014 09:51
URI: http://digre.pmf.unizg.hr/id/eprint/3161

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