Genome sizes of the entomopathogenic nematodes Steinernema carpocapsae and Heterorhabditis bacteriophora (Nematoda: Rhabditida)

There is currently no information on the genome size and complexity in the entomoparasitic nematodes Steinernema and Heterorhabditis. DNA reassociation kinetics were used to determine the genome size and complexity in 2 species: Steinernema carpocapsae and Heterorhabditis bacteriophora. C0t curves derived from renaturation kinetics of denatured DNA indicate that the genomes of these entomoparasitic rhabditids are different both in size and complexity. Genome sizes were estimated at 2·3 × 108 bp for S. carpocapsae and 3·9 × 107 bp for H. bacteriophora and repetitive DNA contents were found to represent 39% and 51% of these respective genomes.

The Aedes aegypti genome: complexity and organization

SummaryWe describe the use of DNA reassociation kinetics to determine the total genome size and complexity together with the individual complexity and copy number of the single copy, middle repetitive and highly repeated DNA fractions of cell line and larval DNA from the mosquito, Aedes aegypti. The genome of Ae. aegypti is both large and complex, being one third the size of the human genome, and exhibits a short period interspersed repeat pattern. The implications of patterns of sequence arrangement and genome complexities for experiments aimed at isolating specific classes of DNA sequences, such as mobile genetic elements, are discussed.

DNA sequence components of the Pinusstrobus nuclear genome

The nuclear DNA of Pinusstrobus L. was characterized by whole-genome hydroxyapatite reassociation kinetics. The genome, which is very large, is not well described by partition into three, four, or five major kinetic components. Instead, it consists of a large array of sequence components with kinetics suggesting a more or less continuous range of frequencies from very large to a single copy. The single-copy fraction, which is estimated to be about 24% of the total, appears to fit the general hypothesis for large genomes, i.e., most of it probably consists of ancient diverged repeated sequences. Under standard conditions of DNA reassociation kinetics, these sequences are not completely diverged but react with kinetics indicating that there is an average of about three repeats for the fraction. It is estimated that only about 0.1% of white pine nuclear DNA is expressed as mRNAs.