[The lampbrush chromosomes of the chicken. Cytological maps of the macrobivalents].

The lampbrush chromosomes (LBC) were prepared from growing oocytes 0.75-1.50 mm in diameter. A map of 6 autosomes and the ZW sex bivalents is presented. Several types of landmarks were noticed: lumpy loops (LL), telomeric bow-like loops (TBL), some large loops in interstitial regions (marker loops--ML). Supposedly, the centromeres of LBC in the chicken are at one of the axial bars bearing no loops. The landmarks PBL and DBL mark the proximal and distal boundaries of bars. LBC-A (probably, chromosome 1 of the chicken karyotype) is about 185 microns. There are 7.3 +/- 0.2 chiasmata. Chiasmata are distributed at quasi-random. In LBC-A one chiasma is localized in a telomere, as a rule. Coordinates of 13 of the 14 different landmarks in LBC-A have been estimated. LBC-B (probably, chromosome 2) is about 151 microns, there are 5.50 +/- 0.23 chiasmata. The LBC-B may be identified by LL-21 and LL-22. LBC-C (probably, chromosome 3) is 128 microns; there are 4.70 +/- 0.18 chiasmata. The chromosome can be identified by characteristic loops LL-31, an unlooped chromomere bar near the telomere (T-32), a characteristic distribution of normal loops along LBC-C: about one half of this LBC bears large loops, and the other one--small loops. LBC-D (chromosome 4?) is 107 microns; there are 3.80 +/- 0.31 chiasmata. Double-loop bridges appear frequently near ML-41. LBC-E (chromosome 5?) is about 72 microns with 2.50 +/- 0.28 chiasmata. There are characteristic TBL loops with abundant RNP material thus being like LL-loops. LBC-F (chromosome 8?) is about 36.5 microns; there are 2 chiasmata. This LBC can be identified by giant telomeric loops GML-F1 and by unlooped bar in the middle of LBC.