In which phase do sister chromatids line up in the middle of the cell, (in 'single-file', without a homologous partner)? Group of answer choices PROPHASE I INTERPHASE TELOPHASE II ANAPHASE II METAPHASE I ANAPHASE I TELOPHASE I METAPHASE II PROPHASE II

The correct answer is ''METAPHASE I.''      

Explanation:

Metaphase I is the stage in which chromosomal studies are generally performed, because its morphology is very clear. The chromosomes, moved by the mitotic spindle, are placed in the center, between the two asters and form the so-called metaphase plate, in which the chromosomes are positioned in such a way that the kinetochore of each sister chromatid are oriented towards the opposite poles. Keeping chromosomes on the cell equator implies a balance between the forces of the microtubules that tend to move the kinetochores toward opposite poles, so positioning them in the center involves a great deal of energy.In each kinetochore, between 20-30 microtubules can be anchored, which exert traction force towards the pole from which they come, so the metaphase plate is maintained by the balance between the opposite forces of the poles on the chromosomes, which hold their sister chromatids by centromeric cohesin.