Define crossing over using the terms -homologous chromosomes, chromatids and crossing over.
Answers
Crossing over is the exchange of genetic material between non-sister chromatids of homologous chromosomes during meiosis, which results in new allelic combinations in the daughter cells.
Crossing over is the swapping of genetic material that occurs in the germline. During the formation of egg and sperm cells, also known as meiosis, paired chromosomes from each parent align so that similar DNA sequences from the paired chromosomes cross over one another.
Crossing over is essential for the normal segregation of chromosomes during meiosis. Crossing over also accounts for genetic variation, because due to the swapping of genetic material during crossing over, the chromatids held together by the centromere are no longer identical.
After crossing-over occurs, the homologous chromosomes separate to form two daughter cells. These cells go through meiosis II, during which sister chromatids separate. In the end, there are four possible gametes. Two of these are called parental because they contain the same alleles as one of the parents.