crossing over

…and reunion, also known as crossing over). In 1916 another student of Morgan’s, Calvin Bridges, used fruit flies with an extra chromosome to prove beyond reasonable doubt that the only way to explain the abnormal inheritance of certain genes was if they were part of the extra chromosome. American geneticist…

…of genes between chromosomes, called crossing over, usually occurs during meiosis, when the total number of chromosomes is halved.

This exchange process, called crossing over, results in chromatids that include both paternal and maternal genes and consequently introduces new genetic combinations. The first meiotic division separates the chromosomal tetrads, with the paternal chromosome (whose chromatids now contain some maternal genes) going to one cell and the maternal chromosome…

…enhanced by the phenomenon of crossing over, in which gene sequences called linkage groups are disrupted, resulting in an exchange of segments between paired chromosomes that are undergoing separation. Thus, although a normal daughter cell produced in meiosis always receives half of the genetic material contained in the parent cell…