Arrest of micronuclear DNA replication during genomic exclusion in Tetrahymena produces haploid strains.
Diploid cells of Tetrahymena thermophila were crossed to strain A*V, whose micronucleus is defective, to induce the unilateral transfer of gametic nuclei from the diploid cells to the A*V cells (round I of genomic exclusion). These haploid nuclei presumably undergo one endomitotic cycle and then become diploid with a G1 (2C) DNA content. However, further DNA replication from 2C to 4C was transiently arrested until the pairs separated. When endomitosis was blocked by treatment with cycloheximide during 6-8 hours of conjugation, the exconjugants of round I of genomic exclusion remained haploid. Competence for diploidization is apparently limited to some period of time after nuclear transfer. Blocking of diploidization during round I of genomic exclusion can be used as an efficient way to induce haploid strains in Tetrahymena.
Kaczanowski
A
A
Zoological Institute, University of Warsaw, Poland.
Gornicka
I
I
Cleffmann
G
G
D000818:Animals; D001345:Autoradiography; D002467:Cell Nucleus; D003227:Conjugation, Genetic; D003513:Cycloheximide / Q000494:pharmacology; D004261:DNA Replication; D004171:Diploidy; D005821:Genetic Techniques; D006238:Haploidy; D008957:Models, Genetic; D013768:Tetrahymena / Q000235:genetics*; D013997:Time Factors
D003513:Cycloheximide