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Nine mutagen sensitive (mus) mutants of Aspergillus nidulans were analyzed for effects on recombination. These mus show increased sensitivity to various mutagens; several were UV-sensitive. The majority were sterile in homozygous crosses homozygous mus diploids were essential to test for mitotic recombination. / Two distinct tests were used: intergenic recombination between colour mutations and their centromeres; and, intragenic recombination between two distinguishable adE alleles. Both hyper- and hypo-rec mus mutations were identified, with 15- to 20-fold differences between them. Three mutations musN, musO, and musQ had greatly elevated recombination frequencies. Only one, musL significantly reduced recombination but consequently increased malsegregation. / Analysis of the genotype of ad$ sp{+}$ recombinants, from musN and musL diploids, revealed qualitative differences from mus$ sp{+}$. musN enhanced mitotic crossing over but not gene conversion; while musL reduced the frequency of simple convertants but increased that of complex homozygous ad$ sp{+}$ genotypes. Mitotic conversion and crossing over, generally associated with each other, were uniquely affected in such mus diploids.

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The purpose of this research was to examine four selected human population groups, institutionalized and normal, to determine the prevalence of the 47, XYY chromosome abnormality among adult males.

Transcription in mammalian and yeast mitochondria proceeds from a few well defined promoters, with processing of polycistronic transcripts producing the mature RNAs. The levels of different sequences in the steady-state RNA populations depend on differential promoter strengths, transcription attenuation and/or selective termination, and differential RNA stabilities. To gain insights into the processes governing transcription and RNA levels in plant mitochondria, a system using isolated maize mitochondria, which synthesize bona fide mitochondrial RNAs, was developed and partially characterized with respect to exogenous requirements and sensitivity to inhibitors of DNA-dependent RNA synthesis. / Although initiation and processing probably occur at reduced levels in isolated maize mitochondria, endogenous DNA templates are extensively transcribed at the same relative rates as in vivo. Isolated maize mitochondria were used to demonstrate that differential rates of both synthesis and turnover help determine the steady-state abundances of various mitochondrial RNA sequences and that mitochondria from certain lines possess an autonomously-replicating, RNA-based genetic system.