Related Experiment Video
Updated: May 16, 2026
11:58
In-Nucleus Hi-C in Drosophila Cells
Published on: September 15, 2021
Maize chromosomal knobs are located in gene-dense areas and suppress local recombination
Rashin Ghaffari1, Ethalinda K S Cannon, Lisa B Kanizay
1Department of Plant Biology, University of Georgia, Athens, GA, USA.
Chromosoma
|December 11, 2012
Summary
Maize knobs, large chromosome regions, were mapped using fluorescence in situ hybridization. Large knobs were found to reduce crossing over locally in maize chromosomes.
Area of Science:
- Genetics
- Cytogenetics
- Maize genomics
Background:
- Knobs are heterochromatic regions on maize chromosomes with variable number, location, and size.
- Previous research suggested knobs might influence recombination, but comprehensive mapping was lacking.
Purpose of the Study:
- To map maize knobs using advanced techniques.
- To investigate the impact of knobs on recombination rates and patterns.
Main Methods:
- Fluorescent in situ hybridization (FISH) was employed to map knobs.
- Two recombinant inbred populations were utilized for genetic mapping.
- Knob positions were accurately placed on the B73 reference genome assembly.
Main Results:
- Seven knobs were successfully mapped, with three precisely located on the B73 genome.
- Knobs were identified in gene-dense genomic regions.
- Large knobs were shown to reduce local crossing over (recombination) by up to twofold on a centimorgan per megabase (cM/Mb) scale.
- This reduction in crossing over was localized to approximately 10 cM on either side of the knobs.
- Linkage disequilibrium among genes near knob regions was not significantly affected.
Conclusions:
- Knob mapping provides crucial genomic context for understanding their function.
- Large maize knobs demonstrably reduce local recombination rates without broadly impacting genome-wide linkage disequilibrium.
- These findings enhance our understanding of chromosome structure and its influence on genetic variation in maize.
Related Concept Videos
02:35Chromatin Position Affects Gene Expression
Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the nucleus greatly influences access to genetic information. Generally, the nucleus' periphery is considered transcriptionally repressive, while the cell's interior is considered a transcriptionally active area.
Topologically Associated Domains (TADs)
The 3-dimensional positioning of chromatin in the nucleus influences the timing and level of...
Topologically Associated Domains (TADs)
The 3-dimensional positioning of chromatin in the nucleus influences the timing and level of...
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...
02:32Position-effect Variegation
In 1928, a German botanist Emil Heitz observed the moss nuclei with a DNA binding dye. He observed that while some chromatin regions decondense and spread out in the interphase nucleus, others do not. He termed them euchromatin and heterochromatin, respectively. He proposed that the heterochromatin regions reflect a functionally inactive state of the genome. It was later confirmed that heterochromatin is transcriptionally repressed, and euchromatin is transcriptionally active chromatin.
02:53Conservative Site-specific Recombination and Phase Variation
Because the DNA segments are cut and reorganized in a direction-specific manner, site-specific recombination has emerged as an efficient genetic engineering technique. Flippase and Cyclization recombinases or Flp and Cre, respectively, are two members of the tyrosine recombinase family derived from bacteriophages, that are used to mediate site-specific DNA insertions, deletions, and targeted expression of proteins in mammalian cell lines.
The recognition sites for Cre recombinase called LoxP...
The recognition sites for Cre recombinase called LoxP...
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...