Related Experiment Video
Updated: Aug 9, 2026
08:38
Scalable Transfection of Maize Mesophyll Protoplasts
Published on: June 23, 2023
Asynchronous replication of heterochromatin in maize
A Pryor1, K Faulkner, M M Rhoades
1Commonwealth Scientific and Industrial Research Organisation, Division of Plant Industry, P.O. Box 1600, Canberra City, Australian Capital Territory, Australia 2601.
Summary
Maize heterochromatin replication patterns reveal that knob heterochromatin replicates last. Increased heterochromatin, especially from B chromosomes, extends DNA replication time, potentially causing chromosome instability.
Area of Science:
- Genetics
- Molecular Biology
- Plant Science
Background:
- Heterochromatin, a condensed form of DNA, plays crucial roles in chromosome structure and function.
- Replication timing of heterochromatin is often asynchronous with euchromatin, impacting genome stability.
- Maize (Zea mays) serves as a model organism for studying chromosome dynamics due to its distinct heterochromatic regions.
Purpose of the Study:
- To investigate the replication patterns of different heterochromatin types in maize chromosomes.
- To determine the relationship between heterochromatin content and the duration of DNA replication.
- To explore the potential role of asynchronous replication in chromosome abnormalities.
Main Methods:
- Analysis of DNA replication patterns in maize chromosomes using cytological techniques.
- Quantification of heterochromatin content, including centromeric, knob, and B-chromosome heterochromatin.
- Correlation of replication timing with heterochromatin dosage.
Main Results:
- Centromeric, B-chromosome distal, and knob heterochromatin exhibit asynchronous late replication, with knob heterochromatin replicating last.
- Nucleolus organizer heterochromatin replicates during euchromatin replication.
- The proportion of S phase dedicated to asynchronous replication is directly proportional to nuclear heterochromatin amount, significantly increased by B chromosomes.
Conclusions:
- Delayed DNA replication of knob heterochromatin may contribute to chromosome segment loss in certain maize genotypes.
- Asynchronous replication, particularly influenced by B chromosomes, is implicated in B-chromosome nondisjunction during pollen development.
Related Concept Videos
01:34Crossing Over
Unlike mitosis, meiosis aims for genetic diversity in its creation of haploid gametes. Dividing germ cells first begin this process in prophase I, where each chromosome—replicated in S phase—is now composed of two sister chromatids (identical copies) joined centrally.
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
The homologous pairs of sister chromosomes—one from the maternal and one from the paternal genome—then begin to align alongside each other lengthwise, matching corresponding DNA positions in a process called synapsis.
In order to...
01:30Crossing Over
Crossing over is the exchange of genetic information between homologous chromosomes during prophase I of meiosis I. Genetic recombination gives rise to allelic diversity in the newly formed daughter cells. In humans, crossing over produces genetically distinct haploid egg and sperm cells that undergo fertilization to produce unique offspring. Before cell division starts, the germ cell’s chromosome(s) undergo duplication in the S phase of the cell cycle. As the cells enter prophase I, duplicated...
02:38Heterochromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions that take up more dye are called heterochromatin. Heterochromatin is further classified into two forms – constitutive heterochromatin and facultative heterochromatin.
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
02:38Heterochromatin
The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions that take up more dye are called heterochromatin. Heterochromatin is further classified into two forms – constitutive heterochromatin and facultative heterochromatin.
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
Constitutive heterochromatin: It is a highly compact region of chromatin that is mostly concentrated in the centromere and telomere. Unlike euchromatin, the amino acid at 9th...
02:31Chromosome Replication
Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone proteins. This process begins at numerous origins of replication during the S phase of the cell cycle in each of a cell’s chromosomes simultaneously. Certain nucleotides can act as origins of replication, but these sequences are not well defined - especially in complex, multi-cellular, eukaryotic species. The length of DNA that spans an origin of...
01:29Replication in Eukaryotes
In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high fidelity before cell division, so there are many proteins that fulfill specialized roles in the replication process. Replication occurs in three phases: initiation, elongation, and termination, and ends with two complete sets of chromosomes in the nucleus.
Many Proteins Orchestrate Replication at the Origin
Eukaryotic replication follows many of the same...
Many Proteins Orchestrate Replication at the Origin
Eukaryotic replication follows many of the same...