Question

During conjugation in Paramecium

• A. out of the four micronuclei formed, three nuclei degenerate
• B. out of the twelve macronuclei formed, four nuclei degenerate
• C. zygote nucleus undergoes ten successive divisions in each conjugant
• D. out of the sixteen nuclei formed from zygote, $12$ become macronuclei and 4 micronuclei

Answer 1

Answer: (A)

out of the four micronuclei formed, three nuclei degenerate

Answer 2

In Paramecium, micronucleus participates in conjugation (sexual exchange). During conjugation, the diploid micronucleus of each conjugant grows in size and then divides by meiosis producing $4$ haploid daughter micronuclei out of which $3$ degenerate and disappear in each conjugant while the remaining one divides by mitosis forming $2$ unequal pronuclei or gamete nuclei-migratory gamete nucleus (smaller) and stationary gamete nucleus (larger). The migratory gamete nucleus of one conjugant passes through the protoplasmic bridge into the other and fuses with the stationary nucleus forming diploid zygote nucleus (synkaryon). In each exconjugant, the zygote nucleus undergoes $3$ successive mitotic divisions producing $8$ nuclei, of which $4$ become macronuclei and $4$ micronuclei. Out of $4$ micronuclei, $3$ degenerate and $1$ remains functional.