Repetitive A-T rich DNA sequences from the Y chromosome of the Mediterranean fruit fly, Ceratitis capitata

Copies of a repetitive DNA sequence distributed over 90% of the length of the long arm of the Y chromosome of the Mediterranean fruit fly, Ceratitis capitata (medfly), have been characterized. Sequencing reveals that these repeats, ranging in size from approximately 1.3 to 1.7 kb, are A-T rich overall (67%). In most cases the repeat units appear to occur in tandemly linked arrays. The repeat copies also all contain a highly similar internal region, approximately 200 bp in length, with a more extreme A-T content bias. This internal region, designated as the AT element, exhibits an A-T content of at least 83%. This exceeds what has been described for any comparable element among invertebrates. Using primers designed from the DNA sequence, PCR amplification of an internal region encompassing the AT element also reveals that these sequences are present only in the male genome in different strains of the medfly.