Abstract
L.) chromosomes were first charac-terized by McClintock (1929) from studies of the first pol-len mitosis. Later, McClintock (1930, 1931, 1933) foundthat pachytene chromosomes showed better morphologicaldetails for cytological studies. The pachytene chromosomeswere identified on the basis of their length, centromere po-sition, prominent chromomeres and heterochromatic knobs(Longley, 1938; Rhoades, 1955; McClintock
Highlights
Maize (Zea mays L.) chromosomes were first characterized by McClintock (1929) from studies of the first pollen mitosis
Other heterochromatic regions found in a number of different chromosome regions have been described: heterochromatin adjacent to the centromeres, heterochromatin of the nucleolar organizer region (NOR), B chromosomes and the abnormal chromosome 10 (Rhoades, 1978)
The identification of mitotic chromosomes using conventional staining was described by Chen (1969) and Filion and Walden (1973), while C-banding procedures have shown the presence of stained distal bands in mitotic chromosomes (Hadlaczky and Kálmán, 1975; Ward, 1980; Aguiar-Perecin, 1985; Rayburn et al, 1985; Jewell and Islam-Faridi, 1994)
Summary
Maize (Zea mays L.) chromosomes were first characterized by McClintock (1929) from studies of the first pollen mitosis. Ward (1980) and Aguiar-Perecin (1985) described differential staining of the classes of maize heterochromatin: heavily stained bands on mitotic chromosomes correspond to knobs, while staining of centric heterochromatin is hardly observed in well-condensed metaphases. The analysis of C-banded mitotic metaphases of maize races with different knob constitutions showed that large bands corresponding to large and medium knobs alter the arm lengths of mitotic chromosomes (Aguiar-Perecin and Vosa, 1985). The analysis of an oat-maize chromosome 9 addition line has revealed that blocks of tandemly arranged 180-bp repeating units are interrupted by insertions of other repeated DNA sequences, mostly represented by individual full-size copies of retrotransposable elements
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