Evolucija kariotipa sisavaca

undergraduate thesis

• Title (english): Mammalian karyotype evolution
• Author: Sven Jurković
• Mentor: Mirjana Pavlica (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2009, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Kariotip neke jedinke se odnosi na broj, veličinu i izgled njezinih kromosoma. Kromosomi pojedinih vrsta predstavljaju širok spektar raznolikosti, od broja do njihove morfologije. Genomi svih vrsta su visoko očuvani i to ne samo u transkribirajućim sekvencama, već i u nekim kromosomski specifičnim nekodirajućim sekvencama ili u poretku gena. Razlike između kariotipa većine vrsta posredovane su različitim razmještajem većih kromosomskih segmenata koji se nazivaju sintenični blokovi. Glavni mehanizam kojim dolazi do takve preraspodjele unutar kromosoma je nasumična homologna rekombinacija u kojoj dolazi do komplementarnog spajanja homolognih regija na nehomolognim kromosomima. Postoje brojne metode za istraživanje kariotipa. Danas najraširenija je fluorescencijska hibridizacija in situ odnosno kromosomsko bojanje u kojima se specifično pripremljeni kromosomi pojedinih vrsta obilježeni fluorokromom hibridiziraju s ljudskim kromosomima. Do spajanja dolazi na mjestima homologije, a signali se vizualiziraju uz pomoć fluorescencijskog mikroskopa. Tom metodom se na jednostavan i precizan način mogu uspoređivati kromosomi određenih vrsta unutar skupine placentalnih sisavaca, dakle svih osim tobolčara te sisavaca koji liježu jaja. Ova metoda nije pogodna niti za usporedbu s ostalim kralježnjacima. Zato se uz tu metodu koristi još i BAC mapiranje u kojima BAC klonirani segmenti mogu poslužiti kao pozicijski markeri duž kromosoma. Istraživanjem takvih preraspodjela kromosomskih segmenata može se saznati mnogo o raznolikosti kariotipa među vrstama. Također, ona su vrlo korisna za proučavanje filogenetskih odnosa organizama, njihovog porijekla od zajedničkog pretka te pretpostavljanju ancestralnog kariotipa. Na temelju toga je za gotovo sve nadredove sisavaca napravljeno evolucijsko stablo koje jasno dočarava njihovu evolucijsku povezanost i podrijetlo od zajedničkog pretka.

Abstract (english)

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.

• Keywords: kariotip; evolucija
• Keywords (english): karyotype; evolution
• Language: croatian
• URN:NBN: urn:nbn:hr:217:023896
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-03-12 11:39:45