Question

In vorticella, the total number of micronuclei formed at the end of pre-zygotic nuclear division in female gamete is
A. 4
B. 6
C. 8
D. 5

Answer 1

Hint: Micronuclei refers to the small nucleus which is formed when a chromosome is not involved in one of the daughter nuclei during cell division and it can also occur in a fragment of the chromosome. It is a condition of gene toxic events and chromosomal instability as micronuclei is commonly seen in cancerous cells.

Complete answer: Vorticella is a genus of bell-shaped ciliates which have stalks that helps to attach the substrate to them. The stalk has contractile myonemes which allow vorticella to pull the cell body against substrates. The formation of stalks occurs after the free-swimming stage which belongs to the family Vorticellidae. Vorticella was first described by Antony van Leeuwenhoek on 9 October 1676. It survives in moist soil, plant roots and mud which live in freshwater environments. The body of vorticella is 30-40 micrometers in diameter and the stalk is 3-4 micrometers in diameter and 100 micrometers long.
Vorticella reproduces by asexual mode by binary fission into two unequal parts. The large-sized cell is the ordinary individual and the other small-sized cell is known as micro-conjugant. The micro conjugant swims and reaches the macro conjugant produced after binary division. Both these cells macronuclei degenerate but the micronuclei undergo mitosis division which leads to the formation of four daughter nuclei.
Hence, the correct option is A, i.e., 4

Note: These solitary organisms have globular bodies when contracted and oval-shaped. They have a pellicle with striae which runs parallel around the cell. There is curved, round micronucleus, and transverse macronucleus near bacteria.