Required for meiotic DNA recombination in females. Probably not involved in DNA repair and recombination in somatic cells.

(UniProt, Q9VF30)

Recombination in homozygous females drastically reduced; total cross over between y and f in the X chromosome reduced from 56% to 2% with distal recombination being more severely affected than proximal. X nondisjunction increased from virtually 0 to 27%. In rec1/rec2, females show a similar reduction for ten regions between al and sp, where crossing over decreases to 9.1%, corresponding to 9% of normal. The number of progeny per homozygous female is reduced 75%; attributed to lethality of nondisjunctional products arising from distributive pairing between noncrossover heterologues. Phenotype of rec/+ is the same as wild-type; rec1 and rec2 homozygotes and hemizygotes have equivalent effects on recombination.

At 17 recombination in rec3/+, rec3/rec3, and rec3/Df(3R)sbd105 is elevated. At 25, the homozygote and the heterozygote display normal values, but recombination in the hemizygote is significantly reduced. At 31, rec3/+ remains normal but rec3/rec3 recombination is drastically reduced. The hemizygote is sterile above 28. In rec2/rec3 females which show the most extreme temperature responses, application of the restrictive temperature at sequential days during development at 25 shows control value activity to be reduced only with treatment on days six and seven, and more precisely during a 36-hour period beginning at the time of pro-oocyte formation between 126 and 132 hours and terminating at 162 hours. This 36-hour period coincides with the boundaries of the S period as well as those of the heat-sensitive period for enhancing recombination in the normal genotype [Grell and Day, 1974, Mechanisms in Recombination (R. F. Grell, ed.). Plenum Press, New York and London, pp. 327-49]. Activity of the rec gene product in the range of 17 to 31 shows a sharp decline between 28 and 31 typical of a protein denaturation curve. If denaturation of a rec protein by the restrictive temperature marks its active phase, then recombination must terminate at the end of S, when the restrictive temperature becomes ineffective. Electron microscopy of serially sectioned oocyte nuclei from rec2/rec3 females maintained at the restrictive or at the permissive temperature reveals synaptonemal complexes indistinguishable in length and fine structure, implicating recombination and not synapsis as the target of the rec gene product.