Reciprocal Translocation In Maize - Part I

Reference:

McClintock, B. 1930. A cytological demonstration of the location of an interchange between two non-homologous chromosomes of Zea mays. Nat. Acad. Sci. 16:791-796.

Brink, R.A., and D.C. Cooper. 1931. The proportion of aborted pollen grains in semisterile-1 plants. Genetics 16:614-628.

Creighton, H.B., and B. McClintock. 1931. A correlation of cytological and genetical crossing-over in Zea mays. Proc. Nat. Acad. Sci. 17:492-497.

Burnham, C.R. 1934. Cytogenetic studies of an interchange between chromosome 8 and 9 in maize. Genetics 19:430-447.

Reciprocal Translocations Cause Semi-sterility.

Crossing-over associated with actual physical exchange of a piece of chromosome.

Creighton and McClintock (1931) used a genetic stock with marker loci and a terminal knob on chromosome nine to show that recombination due to crossover was associated with physical exchange of morphological markers that could be observed through cytological examination. They used reciprocal translocation stock in conjunction with the stock that has a terminal knob on chromosome nine to show that "an actual exchange of pieces of homologous chromosomes accompanies genetic crossing over."

Reciprocal translocations synapsis in meiosis I. McClintock (1930) evaluated the behavior of an interchange between chromosomes 8 and 9 in maize. Chromosome 9 has several marker loci which include the sugary gene, the waxy gene, and a gene for purple aluerone color. Some stocks of maize have a distinct knob on the end of chromosome 9. This knob can be used to identify chromosome 9 during synapsis using root-tip smears at meiosis I. The interchange or reciprocal translocation forms a cross-shaped configuration during prophase I of meiosis when the genetic stock is heterozygous for the translocation. The intersection of the cross configuration is the point where the reciprocal translocation break occurred.