Abstract:

To examine the type, characteristics and meiotic behavior of balanced complex chromosome rearrangements (CCRs) and their relationship with reproductive abnormalities in Chinese people, karyotype analyses were performed in 1063 couples with reproductive abnormalities using G-banding technology. Additional data were retrieved from a Chinese database and analyzed statistically with the karyotype and clinic data of CCRs. Two CCR carriers were found among the 1063 couples, and in all a total of 124 CCR carriers with the complete information were identified in the karyotype analysis and the database search. Our results showed that simple 3-way or 4-way translocations were the most common types, present in 64/124 (51.6%) of CCRs. Double two-way translocations accounted for 26.6% and exceptional CCRs accounted for 21.6% of total cases. General risk of 77.6% for spontaneous abortions and 9.7% for an abnormal child were calculated based on 339 pregnancies of 124 carriers. Pregnancy consequences could be significantly associated with the type of CCRs. Abnormal pregnancy was frequently associated with CCRs on chromosome 8, while dyszoospermia was frequently associated with CCRs on chromosome 1 among the males. The most frequent mode of segregation was 3:3 adjacent-1 (8/12) in 12 abnormal karyotypes. Short chromosomes (groups D-G) were involved in 46.2% of CCRs showing 3:2, 4:2 and 5:3 segregation ratios. In conclusion, carriers of balanced CCRs have a high risk of an abortion and/or a chromosomally unbalanced child. The incidence of spermatogenic defect in male CCR carriers is high, and male infertility is associated with CCRs. Hence, identifying the types of CCRs, chromosomes involved, translocated segments of chromosomes, etc. will provide crucial information for prenatal diagnosis and genetic counseling for carriers of balanced CCRs.

Key words: balanced CCRs, meiosis, reproduction, genetic counseling