Perceptual learning in frequency discrimination.
The Journal of the Acoustical Society of America. 1985-09-01; 78(3): 1118-1120
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1. Genome. 1999 Apr;42(2):308-14.
Recombination nodule mapping and chiasma distribution in spermatocytes of the
pigeon, Columba livia.
Pigozzi MI(1), Solari AJ.
(1)Centro de Investigaciones en Reproduccion, Facultad de Medicina Paraguay 2155
– piso 10(1121) Buenos Aires, Argentina.
Pigeon spermatocytes were processed with a drying-down technique and their
synaptonemal complex (SC) complements were analyzed by electron microscopy. The
synaptonemal complex karyotype of the macrobivalents shows an excellent
correspondence with the mitotic karyotype. The number and distribution of
recombination nodules (RNs) were scored in complete nuclei stained with
phosphotungstic acid. The average number of RNs per nucleus is 64.7. The number
of nodules per bivalent shows a clear linear relationship with SC length in the
10 longest synaptonemal complexes, while the microbivalents usually bear a single
RN. The location of RNs has a non-random distribution along the largest
synaptonemal complexes, with lower frequencies near kinetochores and higher
frequencies toward the telomeres. The ZZ bivalent is the fourth in size and shows
free recombination, having on average 3.8 RNs. The mean number of nodules per
cell and the mean number of nodules in the largest bivalents show very good
agreement with the corresponding number of chiasmata scored in metaphase-I
spermatocytes. It is concluded that the recombination nodules provide a good
check for reciprocal exchanges in this and other species of birds. Additionally,
a new morphology for the recombination nodules is presented, consisting of groups
of electron-dense particles measuring 43 nm in diameter.
PMID: 16671250 [Indexed for MEDLINE]