In sexual reproduction in ciliates the sequence of events is:

Question

A. (1) in each conjugating pair of cells all but one of the four diploid micronuclei disintegrates, (2) then the surviving one undergoes meiosis to produce four haploid micronuclei, of which three also disintegrate, (3) the remaining micronucleus undergoes mitosis to produce two, (4) of which one stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates, (5) the cells separate, each with two nuclei, one of its own and one from its conjugant, (6) one haploid micronucleus in each cell forms a new haploid macronucleus and the other divides mitotically to form eight new haploid micronuclei, (7) the two haploid macronuclei fuse to form a diploid one and the eight haploid micronuclei fuse by pairs into four diploid micronuclei.
B. (1) in each conjugating pair of cells all but one of the four diploid micronuclei disintegrates, (2) then the surviving one undergoes meiosis to produce four haploid micronuclei, of which three also disintegrate, (3) the remaining micronucleus undergoes mitosis to produce two, (4) of which one stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates, (5) the cells separate, each with two nuclei, one of its own and one from its conjugant, (6) the two haploid micronuclei in each cell fuse to form a diploid micronucleus, that (7) divides mitotically, producing diploid macronuclei and micronuclei.
C. A haploid nucleus in an individual of sexual strain (+) divides mitotically and one of the daughter nuclei passes to an individual of sexual strain (-) where it fuses with the resident haploid nucleus to produce a diploid nucleus.
D. (1) in each conjugating pair of cells the four diploid micronuclei fuse, (2) then each undergoes meiosis to produce eight micronuclei, of which seven disintegrate, (3) the remaining micronucleus undergoes mitosis to produce two, (4) of which one stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates, (5) the cells separate, each with two nuclei, one of its own and one from its conjugant, (6) the two haploid micronuclei in each cell fuse to form a diploid micronucleus, that (7) divides mitotically, producing diploid macronuclei and micronuclei.
E. All of the other choices provided are incorrect.

Answer 1

B. (1) in each conjugating pair of cells all but one of the four diploid micronuclei disintegrates, (2) then the surviving one undergoes meiosis to produce four haploid micronuclei, of which three also disintegrate, (3) the remaining micronucleus undergoes mitosis to produce two, (4) of which one stays in the parent cell and the other moves to the opposite cell while the macronucleus in each cell disintegrates, (5) the cells separate, each with two nuclei, one of its own and one from its conjugant, (6) the two haploid micronuclei in each cell fuse to form a diploid micronucleus, that (7) divides mitotically, producing diploid macronuclei and micronuclei.