Cereals are the basis of global agriculture providing more than half of the human food consumption. In Spain, barley is the main crop in terms of growing area, mostly in the poorest agricultural areas. In semiarid areas crop productivity is not only limited by drought, but also by high temperatures at the end of the growth cycle. An increased use of ‘local’ germplasm could lead to the selection of varieties adapted to specific regional conditions. The use of a barley variety like ‘Albacete’, with its proven adaptation to semiarid conditions, can be an excellent option. It has been hypothesized that the high popularity of ‘Albacete’ with farmers particularly in semi-arid areas where barley is grown under rain fed conditions, may be due to the presence of a special form of chromosomal interchange, a reciprocal translocation. This thesis provides a cytological, genetic and agronomic characterization of this reciprocal translocation.

Ο καρυότυπος του οικιακού ποντικού Mus musculus domesticus είναι τυπικά ακροκεντρικός εντούτοις χαρακτηρίζεται από τη συχνή εμφάνιση Rb συντήξεων σε φυσικούς πληθυσμούς. Εξαιτίας αυτών μειώνεται ο 2n από τον τυπικό 2n=40 έως και σε 2n=22 και προκύπτουν στη φύση Rb φυλές, οι οποίες όταν έχουν κοινή προέλευση δημιουργούν Rb συστήματα. Στόχος της διδακτορικής διατριβής ήταν ο λεπτομερής καθορισμός της περιοχής εξάπλωσής του Rb συστήματος της Δ. Πελοποννήσου, η Rb σύσταση και οι σχέσεις των Rb φυλών του και η σχέση του με τον ακροκεντρικό πληθυσμό που το περιβάλλει. Επίσης, να προσδιοριστεί η φυλογενετική πορεία που ακολουθήθηκε στο Rb σύστημα και η πιθανή ειδογένεση που δρομολογείται σε αυτό. Γι’ αυτόν το λόγο, έγινε κυτταρολογική μελέτη σε 232 άτομα του ποντικού από 40 τοποθεσίες της Ελλάδας με τη χρήση των τεχνικών G – και C – ζώνωσης. Βρέθηκε ότι το Rb σύστημα της Δ. Πελοποννήσου αποτελείται κυρίως από 3 Rb φυλές με 2n=24, 28 και 30 και έχει ως κέντρο εξέλιξης την περιοχή της Πάτρας, από όπου εκτείνεται για τουλάχιστον 55 km προς τα Β.-ΒΑ. και για πάνω από 70 km προς τα Ν. Οι παραπάνω Rb φυλές συνδέονται φυλογενετικά μέσω 5 κοινών Rb συντήξεων και είναι πιθανό στην εξέλιξη του Rb συστήματος να έχουν συμμετάσχει και Αμοιβαίες Ανταλλαγές Ολόκληρων Βραχιόνων (WART). Ενδέχεται η μετάβαση από το Rb σύστημα στον ακροκεντρικό πληθυσμό να γίνεται απότομα, ενώ ειδογενετικές διαδικασίες θα ήταν δυνατό να πραγματοποιηθούν μεταξύ των Rb φυλών με 2n=24 και 2n=28, που χαρακτηρίζονται από μερική ομολογία βραχιόνων. / The karyotype of the house mouse Mus musculus domesticus is typically acrocentric, yet it is characterized by the frequent appearance of Rb fusions in natural populations. Due to them, 2n is reduced from the typical 2n=40 even down to 2n=22 and Rb races are formed in the nature, which when linked through common decent, form Rb systems. The goal of this doctorate thesis was the detailed definition of the distribution area of the Rb system of W. Peloponnese, of the Rb constitution and relationship among its Rb races and of its relationship with the surrounding acrocentric population. Also, to clarify the phylogenetic process that was followed in this Rb system and the possible speciation that is under way. Thus, a karyological study was implemented on 232 individuals of the house mouse from 40 Greek localities, using the G – and C – banding staining techniques. It was found that the Rb system of W. Peloponnese consists mainly of 3 Rb races with 2n=24, 28 and 30 and its centre of evolution must lie in the wider Patras area, from where it extends for at least 55 km to the N-NE and for more than 70 km to the S. The above Rb races are phylogenetically related through 5 Rb fusions they have in common and it is possible that Whole Arm Reciprocal Translocations (WART) have contributed to the evolution of this Rb system. The transition from the Rb system to the surrounding typical acrocentric population may occur abruptly, whereas speciation processes could take place between the Rb races with 2n=24 and 2n=28, which are charaterized by monobrachial homology.

Indiana University-Purdue University Indianapolis (IUPUI) / Break-induced replication (BIR) is a mechanism to repair double-strand breaks (DSBs) that possess only a single end that can find homology in the genome. This situation can result from the collapse of replication forks or telomere erosion. BIR frequently produces various genetic instabilities including mutations, loss of heterozygosity, deletions, duplications, and template switching that can result in copy-number variations (CNVs). An important type of genomic rearrangement specifically linked to BIR is half crossovers (HCs), which result from fusions between parts of recombining chromosomes. Because HC formation produces a fused molecule as well as a broken chromosome fragment, these events could be highly destabilizing. Here I demonstrate that HC formation results from the interruption of BIR caused by a defective replisome or premature onset of mitosis. Additionally, I document the existence of half crossover instability cascades (HCC) that resemble cycles of non-reciprocal translocations (NRTs) previously described in human tumors. I postulate that HCs represent a potent source of genetic destabilization with significant consequences that mimic those observed in human diseases, including cancer.