A linear DNA molecule of 5.9 kilobase-pairs is highly homologous to the chloroplast DNA in the green alga Chlamydomonas moewusii.

The unicellular green alga Chlamydomonas moewusii contains small DNA species of unknown cellular location. We report that the most abundant of these DNAs, here designated low-molecular-weight DNA (LMW DNA), is a linear molecule of 5.9 kilobase pairs (kbp). Southern blot hybridization and restriction enzyme analysis revealed that the LMW DNA sequence also exists as an integrated sequence in a discrete region of the chloroplast genome. We have confirmed earlier reports that small DNA species related to the LMW DNA are absent from Chlamydomonas eugametos, an alga which is interfertile with C. moewusii. In the C. eugametos chloroplast genome we found only remnants of the LMW DNA sequence.