Why is crossing over a significant event during meiosis?
1 Answer
Crossing over occurring during meiosis is significant as it brings about recombination of genes inherited from the parents.
Explanation:
Sexual reproduction involves fusion of male and female gametes. The zygote is diploid. One set of chromosomes is contributed by male parent and the other set of chromosomes by the female parent.
The organism develops from the zygote. All the cells in any organism (2 n) have one set of chromosomes from male and the other from female parent. The chromosomes of same type are termed homologous chromosomes.
Pairing of homologous chromosomes occurs during zygotene stage of prophase of meiosis-I. The exchange of chromatid segments of two chromosome of a homologous pair takes place during crossing over occuring in prophase stage.
Thus, at the end of meiosis-II four haploid cells are formed. Two cells carry the chromatids with parental genes only , either from male or female parent while the two other cell will carry the chromatids with exchanged segments. These cells will carry the mixed genes of both the parents. Crossing over thus brings about recombination of genes inherited from the parents.
One can understand this answer properly on observing the diagrams of meiosis from any book one may have on Cell Biology.
Recombination of characters inherited from the parents is brought about during miosis at the time of random orientation of bivalents at metaphase stage of meiosis, in addition to the crossing over occuring during prophase stage.
