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However, unlike E. coli Hfr conjugation, mycobacterial conjugation is chromosome rather than plasmid based. [7] [8] Furthermore, in contrast to E. coli Hfr conjugation, in M. smegmatis all regions of the chromosome are transferred with comparable efficiencies. The lengths of the donor segments vary widely, but have an average length of 44.2kb.
Fact and Fancy is a collection of seventeen scientific essays by American writer and scientist Isaac Asimov. It was the first in a series of books collecting his essays from The Magazine of Fantasy and Science Fiction, and Asimov's second book of science essays altogether (after Only a Trillion). Doubleday & Company first published it in March ...
Paramecium feed on microorganisms such as bacteria, algae, and yeasts. To gather food, the Paramecium makes movements with cilia to sweep prey organisms, along with some water, through the oral groove (vestibulum, or vestibule), and into the cell. The food passes from the cilia-lined oral groove into a narrower structure known as the buccal ...
The final result of conjugation, transduction, and/or transformation is the production of genetic recombinants, individuals that carry not only the genes they inherited from their parent cells but also the genes introduced to their genomes by conjugation, transduction, and/or transformation. [5] [6] [7]
However, studies have shown that when put under nutritional stress, Paramecium aurelia will undergo meiosis and subsequent fusion of gametic-like nuclei. [1] This process, defined as hemixis, a chromosomal rearrangement process, takes place in a number of steps. First, the two micronuclei of P. aurelia enlarge and divide two times to form eight ...
Transformation is a bacterial process for transferring DNA from one cell to another, and is apparently an adaptation for repairing DNA damage in the recipient cell. [14] In addition, plasmids can be exchanged through the use of a pilus in a process known as conjugation. [12]
Studies of Paramecium have contributed to our understanding of the function of meiosis. Like all ciliates, Paramecium has a polyploid macronucleus, and one or more diploid micronuclei. The macronucleus controls non-reproductive cell functions, expressing the genes needed for daily functioning.
In Paramecium tetraurelia, the clonally aging line loses vitality and expires after about 200 fissions, if the cell line is not rejuvenated by conjugation or self-fertilization. The basis for clonal aging was clarified by the transplantation experiments of Aufderheide in 1986 [ 28 ] who demonstrated that the macronucleus, rather than the ...