Question

4. During what phase of meiosis does crossing-over occur? Give a reason why it cannot occur during the following phase (the phase immediately after the phase you chose for the first part of your answer).

Answer 1

Meiosis:

• There are basically two types by which cells dive, Mitosis and Meiosis. Meiosis cell division results in the formation of daughter cells with half the number of chromosomes than the parent cell, whereas the cell division through mitosis results in the formation of genetically identical daughter cells with the same number of chromosomes as there is in the parent cells.
• Meiosis usually occur as two stage process, i.e, Meiosis I followed by a Meiosis II step. Meiosis is the process which is involved with the genetic recombination through the process of crossing over. Crossing over is a process where there is exchange of genetic material between two homologous chromosomes this is done so as to increase the genetic variation within the given population.

Crossing Over Occurs during Prophase I of Meiosis:

• Crossing over, that is the process of exchange of genetic material between two homologous chromosomes, occur during the Prophase I of Meiosis.
• Here the homologous chromosomes gets paired up and they exchange parts during this stage. After the Crossing over process, the chromosomes moves on to the next stage of metaphase pate or the Metaphase I stage. Which is followed by the next Anaphase I as well as the Telophase I phases, where the chromosomes gets separated and gets decondensed after which two cells are formed by Cytokinesis. After Meiosis I, another round of division occurs which is similar to the Mitosis, called the Meiosis II.

Crossing over occurs during Prophase I:

• Crossing over occurs only during the Prophase I of Meiosis I stage, this is because this process occur only between two homologous chromosomes. But the cells become haploid once it completes the Meiosis I stage and can no longer take perform the crossing over process.