Mehanizmi uključeni u evoluciju spolnih kromosoma – opće prihvaćene teorije i nova alternativna paradigma

undergraduate thesis

• Title (english): Mechanisms of sex chromosome evolutionclassical theories and novel alternative paradigm
• Author: Marta Protrka
• Mentor: Višnja Besendorfer (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2022-09-20, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Spolni kromosomi definiraju se kao kromosomi koji sadrže spolno-određujuće gene koji
preusmjeravaju razvoj jedinke na ženski ili muški spol. Teorije o njihovom nastanku i evoluciji
pojavile su se još početkom 20. stoljeća i neke pretpostavke su prihvaćene i danas. Osnovna
teorija o nastanku XX/XY heteromorfnih spolnih kromosoma je o primarnoj pojavi gena koji je
glavni regulator spola na jednom od autosoma te on i njegov homologni kromosom postaju
spolni kromosomi. Predak na kojem se pojavljuju takvi spolni kromosomi smatra se ili
hermafrodit ili jedinka odvojenih spolova koje determiniraju okolišni faktori. Zatim kroz niz
genskih promjena, od kojih je najistaknutija inverzija, dolazi do supresije njihove rekombinacije.
Zatim dolazi do degradacije Y kromosoma i pojave kompenzacijske doze. Analogno se
objašnjava i ZZ/ZW sustav ženske heterogametnosti. Međutim novija istraživanja pokazuju kako
evolucija spolnih kromosoma nije toliko linearna te se dovodi u pitanje mehanizam svake od
pretpostavljenih stadija evolucije. Također kroz razvoj teorija o evoluciji spolnih kromosoma
kroz prošlost bio je zanemaren i ekološki utjecaj koji se u novije vrijeme više istražuje. Ovaj rad
predstavlja pregled i usporedbu nekih od glavnih točaka klasičnih i novijih teorija evolucije
spolnih kromosoma.

Abstract (english)

Sex chromosomes are defined as chromosomes which contain sex-defining genes which direct
the development of an individual to either the female or the male sex. Theories of their
emergence and evolution were made at the beginning of the 20th century and some of them are
considered valid, even today. The classical theory of the creation of XX/XY heteromorphic sex
chromosomes is based on the emergence of a master sex-regulator on one of the autosomes by
which it and its homolog became sex chromosomes. The ancestor which obtained such sex
chromosomes is considered to be either a hermaphrodite or a species which has environmental
sex determination. The next step is suppression of recombination through an assortment of
different genetic changes, the most important one being inversion. Afterwards would be the
degradation of the Y chromosome and the emergence of dosage compensation. The ZZ/ZW
system of female heterogamety is explained accordingly. Despite classical theories having
abundance of evidence, newer research shows that the evolution of sex chromosomes is not that
linear, and the mechanisms of each stage are being questioned. Also, in forming classical
theories of sex chromosomes evolution in the past the influence of ecology was often overlooked,
which will be briefly touched upon here. This paper introduces a review and comparison of some
key points in classical and alternative theories of sex chromosome evolution.

• Keywords: spolni kromosomi; determinacija spola; kromosomski obrat; supresija rekombinacije; kompenzacijska doza
• Keywords (english): sex chromosomes; sex determination; chromosome turnover; recombination suppression; chromosomal dosage compensation
• Language: croatian
• URN:NBN: urn:nbn:hr:217:939050
• 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: 2022-10-04 12:45:28