Mammalian karyotype evolution

Jurković, Sven (2009) Mammalian karyotype evolution. Bachelor's thesis, Faculty of Science > Department of Biology.

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Abstract

A karyotype is the characteristic chromosome complement of species. It represents the number, size and the appearance of chromosomes. The karyotypes of animals display a great diversity, from their number to their morphology. The genomes of all species are remarkably conserved, not only in transcribed sequences, but also in some chromosome-specific non-coding sequences or gene order. Main differences between most of the species karyotype are due to different arrangements of larger chromosomal segments, called syntenic blocks. The principal mechanism of these intra-chromosomal rearrangements is illegitimate homologous recombination. It is the result of accidental crossing-over between homologous segments on non-homologous chromosomes. There are many methods for researching karyotypes. Today, the most common method is fluorescence in situ hibridization, known as chromosome painting. In this technique, chromosome-specific DNA labelled with fluorochromes is hybridized to human probes, which anneal to complementary sequences. The results can be detected by fluorescence microscopy. This method represents a simple and reliable way of comparing chromosomes between species among eutherians, except the marsupials, the mammals that lay eggs and other vertebrats. However, the additional method of BAC mapping is used in which individual BAC clones can be used as positional markers along the length of the chromosome. Rearrangements of these segments into different combinations explains much of the diversity in species karyotypes. Also, such investigations are useful for studying phylogenetic relationships between organisms, their origin from a common ancestor and reconstruction of the ancestral karyotype. Thus, for almost all mammalian superorders, the evolutionary tree is made, which clearly demonstrates their connection and descent from a common ancestor.

Item Type: Thesis (Bachelor's thesis)
Supervisor: Pavlica, Mirjana
Date: 2009
Number of Pages: 20
Subjects: NATURAL SCIENCES > Biology
Divisions: Faculty of Science > Department of Biology
Depositing User: Silvana Šehić
Date Deposited: 18 Dec 2014 12:06
Last Modified: 18 Dec 2014 12:06
URI: http://digre.pmf.unizg.hr/id/eprint/3545

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