Open AccessAbsence of synapsis during pachynema of the normal sized sex chromosomes of Microtus arvalis
Author(s) -
ASHLEY TERRY,
JAAROLA MAARIT,
FREDGA KARL
Publication year - 1990
Publication title -
hereditas
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 50
eISSN - 1601-5223
pISSN - 0018-0661
DOI - 10.1111/j.1601-5223.1990.tb00408.x
Subject(s) - synapsis , chiasma , biology , microtus , meiosis , synaptonemal complex , heterochromatin , centromere , genetics , chromosome , metaphase , chromosomal crossover , zoology , evolutionary biology , gene
The pachytene behavior of the chromosomes of males of Microtus arvalis (Pall.) (Rodentia, Arvicolidae) was examined by electron microscopy in microspread preparations of spermatocytes. There was no synapsis between the axes of these two chromosomes during this period. Since synapsis is universally considered a prerequisite for crossing over and chiasmata formation, disjunction of the sex chromosomes in this species prerequisite for crossing over and chiasmata formation, disjunction of the sex chromosomes in this species must be presumed to be achiasmatic. Unlike previously examined species with no synapsis or crossing over between the X and Y, the sex chromosomes of M. arvalis are of normal size: the X chromosome is of an “original” X size and the Y is a small acrocentric. C‐band studies of M. arvalis mitotic metaphse reveal no blocks of heterochromatin on the sex chromosomes. The implications of these findings are discussed.