During Which Phase Of Meiosis Does Crossing Over Of Chromosomes Occur?
A.Prophase I
B.Metaphase I
C.Anaphase I
D.Telophase I
Answer: A.Prophase I
The exchange of chromosomes takes place in Prophase I of meiosis. This is a very important step of sexual reproduction, as it has an impact on genetic variation in Offspring’s population. In Prophase I several activities occur that pave the way or prepare for the rest of meiosis to happen to produce genetically different gametes.
Homologous chromosomes, (that is one from each parent) align themselves and develop structures known as tetrads or bivalents in Prophase I. These tetrads are formed by four chromatids, two of each homologous chromosome and do so in a very close alignment. Leaving occurs in the process of alignment between one’s sexual orientation and gender identity. Exchange is the process of the actual exchange of genetic material by non-sister chromatids of homologous chromosomes. This process is made easier by the alignment and physical connection that occurs through what is called chiasmata, which are on the non-sister chromatids.
For instance, the homologous chromosome where one chromosome brings genes of blue eyes and straight hair from the mother, and the other chromosome brings genes of brown eyes and curly hair from the father. During crossing over, parts of such chromosomes may swap, leading to a new pairing like a blue-eyed curly-haired gene on one, and a brown eyes and straight hair gene on the other.
This genetic recombination is important because it creates a new combination of the alleles that could not be present in either of the parents which promotes genetic variation in that particular population. That is why, although being offspring of the same parents, siblings can have different combinations of characteristics. Crossing over that happens in prophase I is one of the important phenomena of evolution because it produces new combinations that are adapted to face some challenges.
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