Note that this animal is a translocation heterozygote , having a normal chromosome 1 and 2 in addition to the translocation chromsomes. The diagram above has been simplified considerably by ignoring the crossovers that occurred during meiosis. In a real testis or ovary, the fraction of gametes that are unbalanced would depend upon how crossingover and segregation occured, which is influenced by factors such as the site of the translocated segments. The net result is considerable difficulty in predicting fertility of a translocation carrier. Some of the offspring of translocation carriers are cytogenetically normal, while others carry the translocation of their parent.
Translocations are thus heritable and can be perpetuated in populations.
A centric fusion is a translocation in which the centromeres of two acrocentric chromosomes fuse to generate one large metacentric chromosome. They are also often called Robertsonian translocations , although that term is used by purists to designate a very similar but distinct translocation in which one of the two centromeres is lost. The karyotype of an individual carrying a centric fusion has one less than the normal diploid number of chromosomes. Meiosis in animals carrying a centric fusion chromosome involves formation of trivalents, which is certainly an abnormal structure. Considerable effort has gone into characterizing the effect of this type of translocation on fertility, particularly in cattle and sheep.