Question

Bouquet stage is observed in ................ stage of the cell division.
(a)Leptotene
(b)Zygotene
(c)Diplotene
(d) Pachytene

Answer 1

In many animals, the chromosomes at the prophase stage show definite orientation and polarization and undergo characteristic arrangement. This occurs at a definite stage of meiotic prophase, which represents the onset of the meiotic cycle.

Complete answer:
Bouquet stage is observed in the leptotene stage of the cell division. In many animals, leptotene chromosomes show definite orientation and polarisation. Their tips are often attached to nuclear-envelopement. The remaining part forms a loop that extends to the nucleoplasm. This characteristic arrangement is called the bouquet arrangement. In most cases, this condition persists till the end of zygonema. Leptonema represents the onset of the meiotic cycle. At its beginning, the long and thin chromatin filaments undergo localized and regular coiling to form bead-like chromomeres. Later on, they undergo despiralistaion and condensation and become short and thick. In animal cells, simultaneous with these chromosomal changes, centrioles move to opposite poles, and astral rays appear around each of them.

Additional Information: - Leptotene chromosomes are typically double-stranded. In between two sister chromatids of each chromosome is a dense, non chromosomal, and proteinaceous cementing material, called axial core.
-It is formed of bundles of fine fibrils, surrounded by chromatin. In some plants, chromosomes clump to a dense knot on one side of the nucleus during the leptotene stage.
-This phenomenon is called synizesis. Its significance is not properly understood.
So, the correct answer is 'Leptotene'.

Note: -Meiosis is a peculiar type of cell division occurring in the diploid reproductive cells of all sexually reproducing organisms. -Meiosis forms an essential non-requisite for normal sexual reproduction in plants and animals.
-Meiosis serves as the basic mechanism to maintain genetic continuity and also to conserve species-specific chromosome numbers over successive generations.