Claim · model-written summary
The authors propose that B chromosomes act as parasitic elements controlling knob replication and sperm competition.
- Outcome
- controlling the replication of its proximal heterochromatic knob and increasing the ability of B-containing sperm cells to compete successfully for fertilization of the egge0
- Qualifier
- the B is a parasitic entitye0
Zea maysNot reportedMaterialGeneCompoundOrgan / stageInteractorInteractor roleSecond interactorSecond interactor roleTreatmentComparatorSettingDirectionValue
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the B is a parasitic entity having no genetic function other than controlling the replication of its proximal heterochromatic knob and increasing the ability of B-containing sperm cells to compete successfully for fertilization of the egg.”
t0“MAIZE”
Title
ON THE MECHANISM OF CHROMATIN LOSS INDUCED BY THE B CHROMOSOME OF MAIZE
M M Rhoades; Ellen Dempsey Genetics 1972. doi:10.1093/genetics/71.1.73
Other claims from this paper (17)
- Intervention effect Knobbed regions were frequently eliminated at second microspore division with at least two B chromosomes.
- Intervention effect One B chromosome caused little or no chromatin loss.
- Intervention effect More than two B chromosomes did not increase loss rate.
- Intervention effect B chromosomes from an unrelated strain induced loss as effectively as those from the original high-loss stock.
- Observation B-induced chromatin loss was restricted to knobbed A chromosomes at second microspore division.
- Observation Knobbed chromosomes 3, 5 and 9 each interacted with B chromosomes to cause loss.
- Observation Large-knob chromosomes broke more often than small-knob chromosomes.
- Observation Knobless chromosomes showed negligible loss.
- Association Modifying genes markedly affected chromatin-loss rate.
- Observation Two knobbed heterologous chromosomes had simultaneous loss more often than expected from independent events.
- Observation Joint loss occurred in competent cells.
- Observation B and deficient chromosomes assorted independently at second microspore anaphase.
- Observation Crosses recovered diverse deficient chromosomes, indicating bridge breakage was not confined to the centric region.
- Observation B-chromosome nondisjunction occurred during second microspore mitosis.
- Observation Knobbed chromatin was eliminated during second microspore mitosis.
- Mechanism Faulty heterochromatin replication was proposed to explain nondisjunction and breakage.
- Mechanism Position of nonreplicating segments was proposed to determine nondisjunction versus breakage.