The mitochondrial genome of wild-type yeast cells

Putative origins of replication in the mitochondrial genome of yeast

“…The finding of the 80 nucleotide sequence in the mitochondrial genome of aT,7,8 strongly suggests that this sequence is also present in the genomes of aT/7/12/1 and a3/1 (see [2]) since these encompass that ofa* 1,7,8. If this is the case, then all 6 spontaneous petite genomes studied by us [2] contain the sequence under consideration, in spite of their origin from 3 distinct regions of the parental wild-type genome.…”

“…The finding of the 80 nucleotide sequence in the mitochondrial genome of aT,7,8 strongly suggests that this sequence is also present in the genomes of aT/7/12/1 and a3/1 (see [2]) since these encompass that ofa* 1,7,8. If this is the case, then all 6 spontaneous petite genomes studied by us [2] contain the sequence under consideration, in spite of their origin from 3 distinct regions of the parental wild-type genome. Interestingly, one of these petites (b) originated in fact from a different parental wild-type strain (strain B) compared to ail the others which originated from strain A; its DNA showed, however, the same hybridization pattern on restriction fragments from the mitochondrial DNAs of both B and A.…”

“…The restriction maps of the repeat units of the mitochondrial genomes under consideration are given in fig.2; both these 'petite' genomes and the genomes of their parental wild-type strains (A,B) have beer1 extensively investigated [2,5]. The regions of wild-type strain genomes from which the petite genomes of fig …”

“…Excised segments may originate from different regions of the wild-type genome unit, may have different sizes, and are highly conserved in sequence [2]. It has been suggested that, in the case of spontaneous 'petite' mutants, such segments contain an origin of replication, implying that the wild-type genome unit contains several origins of replication [3 1.…”

Repeated sequences in the mitochondrial genome of yeast

“…Segment I ( fig.1) is the repeat unit of the mitochondrial genome of 'petite'mutant a-l/lR/l [3,4]; this originated from the region around the 15 S RNA gene [3,7]. Segment II(fig*l~is~~~ II fragment 2 of 'petite' mutant DS 401 [S]; this was the putative locus of the var I gene and is located roughly opposite to segment I on the circular map of the mitochondrial genome.…”