An X1X1X2X2/X1X2Y mechanism of sex determination in a South American rodent, Deltamys kempi (Rodentia, Cricetidae)

• Published in: Cytogenetics and cell genetics Vol. 38; no. 1; p. 50
• Main Authors: Sbalqueiro, I J, Mattevi, M S, Oliveira, L F
• Format: Journal Article
• Language: English
• Published: Switzerland 1984
• Subjects: Animals; Arvicolinae - genetics; Chromosome Banding; Female; Karyotyping; Male; Meiosis; Sex Determination Analysis; South America; X Chromosome; Y Chromosome; South America
• ISSN: 0301-0171
• DOI: 10.1159/000132029

Chromosome studies on 14 specimens of Deltamys kempi disclosed six males with 2n = 37, NF = 38, six females with 2n = 38, NF = 38, and two females with 2n = 37, NF = 38. G- and C-band analyses revealed a Y-autosome translocation in the males leading to a multiple chromosome system of sex determination of the type X1X1X2X2/X1X2Y, this being the second case of such a mechanism described in rodents. At meiosis the males presented a trivalent in which C-banding studies showed an alternate orientation of the sex chromosomes due to end-to-end association of the X1 and Y chromosomes, the Y and the X2 being held together by interstitial chiasmata. At metaphase II both n = 17 + Y and n = 18 + X1 are regularly observed. The two females with 2n = 37, NF = 38, are heterozygous for an autosomal centric fusion involving chromosomes 1 and 13. The product of the Y-autosome translocation constitutes the largest element of the karyotype (9.4% of the haploid set); the X1 chromosome amounts to 7.8% of this set, including a large heterochromatic block. When only its euchromatic region is considered, this percentage decreases to 4.6%. From two to seven NORs were observed at the telomeres, with a mean of 4.4 +/- 1.1 per cell.