A 100%-complete sequence reveals unusually simple genomic features in the hot-spring red alga Cyanidioschyzon merolae

<p>Abstract</p> <p>Background</p> <p>All previously reported eukaryotic nuclear genome sequences have been incomplete, especially in highly repeated units and chromosomal ends. Because repetitive DNA is important for many aspects of biology, complete chromosomal structures are fundamental for understanding eukaryotic cells. Our earlier, nearly complete genome sequence of the hot-spring red alga <it>Cyanidioschyzon merolae </it>revealed several unique features, including just three ribosomal DNA copies, very few introns, and a small total number of genes. However, because the exact structures of certain functionally important repeated elements remained ambiguous, that sequence was not complete. Obviously, those ambiguities needed to be resolved before the unique features of the <it>C. merolae </it>genome could be summarized, and the ambiguities could only be resolved by completing the sequence. Therefore, we aimed to complete all previous gaps and sequence all remaining chromosomal ends, and now report the first nuclear-genome sequence for any eukaryote that is 100% complete.</p> <p>Results</p> <p>Our present complete sequence consists of 16546747 nucleotides covering 100% of the 20 linear chromosomes from telomere to telomere, representing the simple and unique chromosomal structures of the eukaryotic cell. We have unambiguously established that the <it>C. merolae </it>genome contains the smallest known histone-gene cluster, a unique telomeric repeat for all chromosomal ends, and an extremely low number of transposons.</p> <p>Conclusion</p> <p>By virtue of these attributes and others that we had discovered previously, <it>C. merolae </it>appears to have the simplest nuclear genome of the non-symbiotic eukaryotes. These unusually simple genomic features in the 100% complete genome sequence of <it>C. merolae </it>are extremely useful for further studies of eukaryotic cells.</p

The Problems of Re-adjustment to Civilian Life of Japanese-American Evacuees From the West Coast

Background of Study. It is generally recognized that children of immigrants to America, the second-generation, have a degree of difficulty in adjusting to American ways. The Nisei, are the second-generation of Japanese immigrants, who have adopted most of the prevailing customs and attitudes of those Americans about them but find that they are unable to free themselves entirely from the influence of their parents’ origin. Their cultural background and in the majority of cases the inferior social and occupational status into which they are born has a great influence upon them. Therefore, one finds that their problems of adjustment date back to their birth in an immigrant family. Upon examination of the Nisei’s problems, they do not differ too greatly from those of other racial minority groups. One of their problems is an occupational problem. Japanese are not hired in the more desirable positions as readily as the Caucasians. Reasons for this are the oppositions from fellow employees and also from clientele of the different employers they may be working for. The Japanese have not been able to be self-sufficient within themselves because of the lack of numbers. Another very pressing and crucial problem in their lives is their lack of social acceptance. They are not socially accepted in many Caucasian groups and in the majority of cases the extent of their contact with Caucasians is in the school situation. Both of these problems have been a source of insecurity to them and has made their adjustment to Caucasian groups rather difficult

Suppression of Repeat-Mediated Gross Mitochondrial Genome Rearrangements by RecA in the Moss Physcomitrella patens[C][W]

RecA and its ubiquitous homologs are crucial components in homologous recombination. Besides their eukaryotic nuclear counterparts, plants characteristically possess several bacterial-type RecA proteins localized to chloroplasts and/or mitochondria, but their roles are poorly understood. Here, we analyzed the role of the only mitochondrial RecA in the moss Physcomitrella patens. Disruption of the P. patens mitochondrial recA gene RECA1 caused serious defects in plant growth and development and abnormal mitochondrial morphology. Analyses of mitochondrial DNA in disruptants revealed that frequent DNA rearrangements occurred at multiple loci. Structural analysis suggests that the rearrangements, which in some cases were associated with partial deletions and amplifications of mitochondrial DNA, were due to aberrant recombination between short (<100 bp) direct and inverted repeats in which the sequences were not always identical. Such repeats are abundant in the mitochondrial genome, and interestingly many are located in group II introns. These results suggest that RECA1 does not promote but rather suppresses recombination among short repeats scattered throughout the mitochondrial genome, thereby maintaining mitochondrial genome stability. We propose that RecA-mediated homologous recombination plays a crucial role in suppression of short repeat-mediated genome rearrangements in plant mitochondria