Written By: Plasmid, in microbiology, an extrachromosomal genetic element that occurs in many bacterial strains. Plasmids are circular deoxyribonucleic acid (DNA) molecules that replicate independently of the bacterial chromosome. They are not essential for the bacterium but may confer a selective advantage.
A gnat /ËnÃ¦t/ is any of many species of tiny flying insects in the Dipterid suborder Nematocera, especially those in the families Mycetophilidae, Anisopodidae and Sciaridae. They can be both biting and non-biting. Most often they fly in large flocks resembling clouds.
Key facts. 1  The fruit fly (Drosophila melanogaster, â Drosophila â hereafter) is the most extensively used and one of the most well understood of all the model organisms. 2  Drosophila fruit flies measure approximately 3 mm in length. 3  Drosophila larvae are small, white and glossy with a similar appearance to worms.