Complex sentence: Most of these linear mtDNAs possess telomerase independent telomeres (i.e. the ends of the linear DNA) with different modes of replication, which have made them interesting objects of research, as many of these unicellular organisms with linear mtDNA are known pathogens.
Split into simpler sentences: Most of these linear mtDNAs possess telomerase independent telomeres, (i.e. the ends of the linear DNA), with different modes of replication. This has made them interesting objects of research, for many of these unicellular organisms with linear mtDNA are known pathogens.