Objective: To investigate the source of the extra small chromosome in a patient with karyotype 45,X[115]/46,X + mar[45]/46,XY[29].
Methods: The SRYgene was detected by PCR, and the chromosome Y probe that labeled with biotin was detected by fluorescence in situ hybridization.
Results: SRY gene is detected positive and the mar chromosome showed positive signal with FISH in human chromosome Y probe pool.
Conclusion: The extra small chromosome is part of the chromosome Y.