Question

Micronucleus and macronucleus are the characteristic features of
(a) Balantidium and Hydra
(b) Vorticella and Nyctotherus
(c) Opalina and Nyctotherus
(d) Vorticella and paramecium

Answer 1

Hint:
It is a ciliate protozoan that comes under the order Peritrichida. This is a bell-shaped organism that has a conspicuous ring of cilia on the oral end and a contractile unbranched stalk on the aboral end. Another organism is a genus of eukaryotic, unicellular ciliates. These are found in freshwater, brackish water, and marine environments.

Complete step by step answer:
Dimorphic nuclei are the feature of ciliates. Paramecium and vorticella have dimorphic nuclei i.e., two kinds of nuclei i.e., micronucleus and macronucleus. Micronucleus is inactive and activates at the time of cell division and also controls sexual reproduction. The macronucleus helps in the metabolic function of the cell and it also controls asexual reproduction.
Micronucleus is the extra-nuclear body that contains damaged chromosome fragments and the complete chromosome does not go into the nucleus after cell division. It behaves as a germline nucleus that does not express its genes. Micronucleus is a membrane-bounded structure that is small in size that has DNA content under the nuclear envelope and gets separated from the primary nucleus. Dimorphic nuclei are seen in protozoan ciliates, tetrahymena, and foraminifera.
Hence the correct answer is vorticella and paramecium

Option ‘D’ is correct

Note:
Micronucleus has long been linked to chromosome instability, genome rearrangements, and mutagenesis. The nuclear RNA for vegetative growth is provided by the macronucleus. When cells mate they exchange haploid micronucleus and a new macronucleus develops from a new diploid micronucleus.