| Abstract |
Doubly uniparental inheritance (DUI) of mitochondrial DNA (mtDNA) is an unusual feature found in marine mussels and a few other bivalve species. These species have two types of mitochondrial DNA: one that is transmitted from mother to both female and male offspring (F type) and one that is transmitted from the father to sons only (M type). The two molecules have, therefore separate transmission routes, one through the female and the other through the male lineage. In most cases the two molecules differ by more than 20%. But there are exceptions in which the M genome is very similar with the F genome. This is referred to as masculinization of the F genome and might lead to a role reversal in which an old F genome enter the male lineage displacing M type molecules and setting the differentiation time of the two lineages to zero. Recent evidence exists that mtDNA undergoes homologous recombination. This led to the hypothesis that the so called masculinized F genomes are actually recombined molecules that acquired those specific sequence from the M genome that specify the characteristic M behavior. The present thesis tries to obtain direct evidence whether F or recombinant mtDNA molecules are transmitted via sperm to the next generations, whether mtDNA recombination is a general or restricted phenomenon, and the relation of recombination with the phenomenon of masculinization. Sperm from 38 different male mussels was examined. The analysis was focused mainly on the large region of the mtDNA genome with no known function (LUR: Large Unassigned Region), which is suspected to carry the specific sequence that modify the behavior of M molecules. The results support the view that there is a strong mechanism that exclude the presence of F molecules in the sperm. In addition it seems that there is also a mechanism that either prohibit the recombination between F and M molecules in typical male individuals, either that recombinant molecules, in case they are produced in male gonad, cant pass into sperm.
|
Διερεύνηση των τύπων mtDNA που μεταφέρονται με το σπέρμα και η σχέση με το σύστημα της διπλής μονογονικής κληρονόμησης του mtDNA του μυδιού Mytilus galloprovincialis
