How the Body Works: Crossing-over

The process of crossing-over, which occurs during meiosis, is one the most important genetic events, for it guarantees the individual characteristics of each one of us. When the two homologous chromosomes lie side by side, breaks occur in the chromosomes and corresponding lengths of the chromosome are interchanged. This crossing-over disrupts the original sequence of alleles and interchanges parts of both maternal and paternal chromosomes so that the possible number of gametes with different genetic information that any individual can produce is almost incalculable. This is why a child may inherit his father's nose and his mother's eyes.