Mutation affecting cell separation and macronuclear resorption during conjugation inTetrahymena thermophila: Early expression of the zygotic genotype
✍ Scribed by Kaczanowski, Andrzej
- Publisher
- John Wiley and Sons
- Year
- 1992
- Tongue
- English
- Weight
- 831 KB
- Volume
- 13
- Category
- Article
- ISSN
- 0192-253X
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✦ Synopsis
A new recessive conjugation lethal mutation was found in Tefruhymenu fhermophilu which was named mru for macronuclear resorption arrest. Other events affected by the mru mutations are separation of pairs, DNA replication in the macronuclear anlagen, and resorption of one of the two micronuclei. In wild-type crosses 50% of the pairs had separated by 12 hr after mixing two mating types and had completed resorption of the old macronucleus 1-2 hr later. In contrast most mru conjugants did not separate even by 24 hr after mixing and the old relic (condensed) macronucleus was seen in over 90% of them.
After addition of 10 mM calcium to the conjugation medium, the mru conjugants did separate but they still failed to complete resorption of the old macronucleus and to replicate macronuclear anlagen DNA in the exconjugants. The calcium induced separation of the mru conjugants occurred later than the separation of control pairs.
During normal conjugation cell separation occurs before the first expression of known macronuclear genes and prior to processing of the macronuclear DNA. Therefore, the mru phenotype infers that separation of conjugants requires a signal which is produced by the macronuclear anlagen at an unusually early time.