[Parental effects of conditional mutations and their explanations]

A study of the properties of conditional dominant and recessive lethals in Drosophila melanogaster has demonstrated parental effects in the inheritance and manifestation of these mutations. Maternal and paternal effects are present when conditional mutations interact with (1) one another, (2) the Y chromosome, or (3) chromosomal rearrangements, as well as (4) when the visual expression of a conditional mutation is inherited or (5) during the formation ofmorphoses (monstrosities) in mutant offspring. The maternal and paternal effects do not exclude one another: the same mutation can display both patterns. The characters manifesting themselves at late developmental stages (morphoses) are inherited according to a parental effect pattern. A general concept of the parental effect is proposed and its types are classified.