Question

Compare between metaphase I and metaphase II of meiosis.

Answer 1

Hint: Meiosis may be a sort of cellular division that reduces the number of chromosomes within the parent cell by half and produces four gamete cells. This process is required to supply egg and sperm cells for amphimixis. The homologous pair may be a representation of an equivalent DNA but has different alleles.

Complete answer:
a) Metaphase I: Metaphase is a stage in the cell cycle where all the genetic material is condensed into chromosomes. These chromosomes then become visible. During this stage, the nucleus disappears and therefore, chromosomes appear within the cytoplasm of the cell. It is a stage of cell division (mitosis or meiosis). Usually, individual chromosomes can't be observed within the nucleus. However, during metaphase of mitosis or meiosis, chromosomes condense and become distinguishable as they align within the centre of the dividing cell. Metaphase chromosomes are used during the karyotyping procedure to search for chromosomal abnormalities.
b) Metaphase II -In metaphase II, the chromosomes line up individually along with the metaphase plate. In anaphase II, the sister chromatids separate and are pulled towards opposite poles of the cell. In telophase II, nuclear membranes form around each set of chromosomes, and therefore the chromosomes decondense.
The major difference between metaphase I and metaphase II is:-
Metaphase I: Microtubules of 1st pole are attached to kinetochores of 1st of the 2nd chromosomes facing to an equivalent pole.
Metaphase II: Microtubules are attached to the kinetochores of the centromere on either side of the chromosome.

Note: In humans (2n=46), there are 46 chromosomes present during metaphase, but 92 chromatids. It is only sister chromatids that separate, which is a step signalling that anaphase has begun and every chromatid is taken into account as a separate individual chromosome.