Question

Lampbrush chromosomes are seen in which typical stage?
A.Mitotic anaphase
B.Mitotic prophase
C.Mitotic metaphase
D.Meiotic prophase

Answer 1

Hint: Lampbrush chromosomes are first identified in growing oocytes by Walther Fleming. They can be distinguished by the structure formation. This stage in the cell division lives for some time and helps in the building up of the mRNA molecules and few other modifications for the formation of one new individual.

Complete answer:
A.Mitotic anaphase: During this step of cell division the chromosomes which underwent modification separate and move to the opposite side of each other. The movement of chromosomes to the centromeres is called anaphase. So, option A is not correct
B.Mitotic prophase: during this phase the nucleus disappears and the chromatin material in the cell during this time of division it condenses into chromosomes which slowly by further changes lead to the formation of mitotic spindle. So, option B is not correct.
C.Mitotic metaphase: In this phase of cell division the spindles which are formed come together and form a metaphase plate so that all the chromosomes are lined up at the centre of the cells in one thin imaginary plane. So, option C is not correct
D. Meiotic prophase: in this phase of cell division the nucleolus disappears and the chromosomes inside the cell material undergo crossing over where during prophase diplotene stage bivalents or the two sister chromatids transform into structure modification which can be observed as the lamp brush form

Hence, the correct answer is option (D).

Note: By the electron microscopy studies in the xenopus laevis oocyte the extension of chromosome axis is seen during the Lampbrush stage of meiotic prophase stage which is linked to the production of high molecular weight non- ribosomal RNA. The oocytes which are obtained for the study of Lampbrush formation must be free of contaminating cells such as follicle cells.