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Proceedings of the National Academy of Sciences of the United States of America logoLink to Proceedings of the National Academy of Sciences of the United States of America
. 1980 Nov;77(11):6705–6709. doi: 10.1073/pnas.77.11.6705

Asynchronous replication of heterochromatin in maize

A Pryor 1, K Faulkner 1, M M Rhoades 1,*, W J Peacock 1
PMCID: PMC350357  PMID: 16592919

Abstract

Replication patterns of four classes of heterochromatin in the chromosomes of maize were analyzed. Centromeric heterochromatin, distal heterochromatin of the B chromosomes, and knob heterochromatin all have asynchronous late replication, knob heterochromatin being the last chromosomal DNA to complete replication. Nucleolus organizer heterochromatin replicates during the period of euchromatin DNA replication. The proportion of the S period involved in asynchronous late replication is directly dependent on the amount of heterochromatin in the nucleus. Both additional knob and B-chromosome heterochromatin participate in this effect. Each additional B chromosome produces an increment in the proportion of nuclei with asynchronous replication; in nuclei with 12 B chromosomes, the proportion of the S phase showing asynchronous late replication is more than 3 times greater than that in nuclei without B chromosomes. The data are consistent with the hypothesis that delayed DNA replication of knob heterochromatin is responsible, in some genotypes, for the loss of chromosome segments and for B-chromosome nondisjunction in the second pollen grain mitosis.

Keywords: B chromosomes, nondisjunction, late replication

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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