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Size polymorphism of the X-chromosome due to attachment of a B-chromosome in the Medfly, Ceratitis capitata (Wied.)

Alicia Basso^I; Ernesto Lifschitz^II

^IFacultad de Agronomia, Cátedra de Genética, Universidad de Buenos Aires, Avenida San Martin 4453, 1417 Buenos Aires, Argentina
^IILaboratorio de Genética de Insectos, Instituto de Genética, I.N.T.A., C.C. 25, 1712 Castelar, Argentina. Send correspondence to E.L.

ABSTRACT

A chromosomal polymorphism affecting the length of the long arm of the X-chromosome, along with the presence of a B-chromosome is reported in a laboratory population of Ceratitis capitata. The observed B-chromosome is small, heterochromatic and telocentric. It was found, in both sexes, in somatic cells (cerebral ganglia tissue) as a free chromosome, or terminally attached to the long arm of the X-chromosome, giving the appearance of a larger X chromosome. Males transmit both free B and large X-chromosomes to their progeny. Females only transmit large X to their progeny, at a higher rate than they do the standard X, suggesting either a differential utilization of the ovules carrying the large X or a preferential coorientation during the first meiotic division.

Keywords: polymorphism; X-chromosome; B-chromosome; Medfly; Ceratitis capitata.

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