Real-Time Pcr For Sexing And Cytological Analysis Of The Synapsis Of The Smallest Bivalent In Pachytene Spermatocytes Of Oreochromis Niloticus

The aim of the present study was to report new molecular markers for real-time PCR associated with X and Y sex chromosomes, and perform analysis of the synapsis of the smallest bivalent in pachytene spermatocytes of XY male Oreochromis niloticus. Four pairs of primers were designed and were tested by endpoint PCR and real-time PCR using SYBR Green detection system in DNA samples from XX females, XY males and YY supermales. In order to assess the smallest bivalent synapsis, testicular samples from XY males were used to make chromosomal spreads in pachytene. Size range of fragments amplified by endpoint PCR was concordant with the expected values. Real-time PCR assay showed equal specificity but speed advantage in amplification detection of markers associated with X and Y chromosomes according to the established PCR conditions. Genetic differences between regions of the X and Y chromosomes (smallest bivalent) proven with specific markers were not cytological perceptible in pachytene spermatocytes from XY O. niloticus. A model of XY bivalent synapse was suggested based on the DNA sequences homologies and differences between KC710223 and KC710224 accessions from X and Y chromosomes.