Abstract
Presynaptic association of homologous chromosomes is a prerequisite to the sequence of events that lead to chiasma formation. This association of homologous chromosomes, as entire units, occurs with probability a, and chiasma formation occurs independently in opposite chromosome arms with probability c. a and c have been estimated from frequencies of different chromosome configurations at metaphase I of euhexaploid wheat and several derived lines. In the euploid, a is essentially unity and c is of the order of 95%. All changes in the aneuploidy studied involved c rather than a, whereas the change induced by colchicine application primarily involved a.-Observed and expected frequencies of configurations were compared in wheat hybrids in which only homoeologues were present. The expected frequencies of configurations were estimated from the data, based on a being unity for entire groups of homoeologues and c being the probability of chiasma formation between random homoeologous arms. Observed and expected frequences of configurations were in general agreement; however, an excess of observed closed bivalents at the expense of multivalents is interpreted to mean that not all homoeologues are effectively associated in all cells.-In euhexaploid wheat, we suggest that homologues associate with almost certainty, whereas homoeologous pairs of chromosomes associate less efficiently. The aneuploidy examined in this study does not appear to affect the association of chromosomes, but rather the number of chiasmata that eventuate and, in the case of deficiency of chromosome 5B, the distribution of chiasmata within homoelogues, perhaps by way of rendering sites for chiasma formation of homoelogues more similar.
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Claims 10
Claim · model-written summary
In euploid wheat, homologous chromosome association probability a was essentially unity.
- Taxon
- wheat
Triticum aestivume1 - Outcome
- a is essentially unitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In the euploid, a is essentially unity”
e1“euhexaploid wheat and several derived lines”
Claim · model-written summary
In euploid wheat, chiasma formation probability c was about 95%.
- Taxon
- wheatTriticum aestivume1
- Outcome
- ce0
- Value
- 95%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“c is of the order of 95%”
e1“euhexaploid wheat and several derived lines”
Claim · model-written summary
Studied aneuploid changes affected c rather than a.
- Taxon
- wheatTriticum aestivume1
- Outcome
- c rather than ae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All changes in the aneuploidy studied involved c rather than a”
e1“euhexaploid wheat and several derived lines”
Claim · model-written summary
Colchicine primarily changed association probability a.
- Taxon
- wheatTriticum aestivume1
- Treatment
- colchicine applicatione0
- Outcome
- ae0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the change induced by colchicine application primarily involved a”
e1“euhexaploid wheat and several derived lines”
Claim · model-written summary
Observed and expected chromosome configuration frequencies generally agreed in wheat hybrids.
- Taxon
- wheatTriticum aestivume1
- Outcome
- frequences of configurationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Observed and expected frequences of configurations were in general agreement”
e1“wheat hybrids”
Claim · model-written summary
Wheat hybrids had excess closed bivalents relative to expected frequencies at the expense of multivalents.
- Taxon
- wheatTriticum aestivume1
- Outcome
- observed closed bivalentse0
- Direction
- excesse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“an excess of observed closed bivalents at the expense of multivalents”
e1“wheat hybrids”
Claim · model-written summary
The excess closed bivalents suggests that homoeologues are not effectively associated in every cell.
- Taxon
- wheatTriticum aestivume1
- Outcome
- not all homoeologues are effectively associated in all cellse0
- Qualifier
- excess of observed closed bivalentse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“not all homoeologues are effectively associated in all cells”
e1“wheat hybrids”
e2“an excess of observed closed bivalents at the expense of multivalents”
Claim · model-written summary
Homologues were inferred to associate almost certainly in euhexaploid wheat, while homoeologous pairs associated less efficiently.
- Taxon
- wheatTriticum aestivume1
- Outcome
- homoeologous pairs of chromosomes associate less efficientlye0
- Direction
- less efficientlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“homologues associate with almost certainty, whereas homoeologous pairs of chromosomes associate less efficiently”
e1“In euhexaploid wheat, we suggest that homologues”
Claim · model-written summary
Aneuploidy affected chiasma number rather than chromosome association.
- Taxon
- wheatTriticum aestivume1
- Outcome
- number of chiasmata that eventuatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“aneuploidy examined in this study does not appear to affect the association of chromosomes, but rather the number of chiasmata that eventuate”
e1“In euhexaploid wheat, we suggest that homologues”
Claim · model-written summary
Chromosome 5B deficiency may change chiasma distribution among homoeologues.
- Taxon
- wheatTriticum aestivume1
- Material
- chromosome 5Be0
- Outcome
- distribution of chiasmata within homoeloguese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in the case of deficiency of chromosome 5B, the distribution of chiasmata within homoelogues”
e1“In euhexaploid wheat, we suggest that homologues”