Abstract
Recombination nodules (RNs) are closely correlated with crossing over, and, because they are observed by electron microscopy of synaptonemal complexes (SCs) in extended pachytene chromosomes, RNs provide the highest-resolution cytological marker currently available for defining the frequency and distribution of crossovers along the length of chromosomes. Using the maize inbred line KYS, we prepared an SC karyotype in which each SC was identified by relative length and arm ratio and related to the proper linkage group using inversion heterozygotes. We mapped 4267 RNs on 2080 identified SCs to produce high-resolution maps of RN frequency and distribution on each bivalent. RN frequencies are closely correlated with both chiasma frequencies and SC length. The total length of the RN recombination map is about twofold shorter than that of most maize linkage maps, but there is good correspondence between the relative lengths of the different maps when individual bivalents are considered. Each bivalent has a unique distribution of crossing over, but all bivalents share a high frequency of distal RNs and a severe reduction of RNs at and near kinetochores. The frequency of RNs at knobs is either similar to or higher than the average frequency of RNs along the SCs. These RN maps represent an independent measure of crossing over along maize bivalents.
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Claims 8
Claim · model-written summary
An SC karyotype identified each maize SC and linked it to a linkage group.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“we prepared an SC karyotype in which each SC was identified by relative length and arm ratio and related to the proper linkage group using inversion heterozygotes”
t0“Zea mays”
Claim · model-written summary
Maps were produced from 4267 RNs on 2080 SCs.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We mapped 4267 RNs on 2080 identified SCs to produce high-resolution maps of RN frequency and distribution on each bivalent”
t0“Zea mays”
Claim · model-written summary
RN frequency correlated closely with chiasma frequency and SC length.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RN frequencies are closely correlated with both chiasma frequencies and SC length”
t0“Zea mays”
Claim · model-written summary
The RN map was about twofold shorter than most maize linkage maps.
- Outcome
- total length of the RN recombination mape0
- Direction
- shortere0
- Value
- about twofolde0
- Comparator
- most maize linkage mapse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The total length of the RN recombination map is about twofold shorter than that of most maize linkage maps”
t0“Zea mays”
Claim · model-written summary
Relative lengths of individual bivalent maps corresponded well.
- Outcome
- relative lengths of the different mapse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there is good correspondence between the relative lengths of the different maps when individual bivalents are considered”
t0“Zea mays”
Claim · model-written summary
Each bivalent had a unique crossover distribution.
- Outcome
- unique distribution of crossing overe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Each bivalent has a unique distribution of crossing over”
t0“Zea mays”
Claim · model-written summary
All bivalents had high distal RN frequency and reduced RN frequency near kinetochores.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“all bivalents share a high frequency of distal RNs and a severe reduction of RNs at and near kinetochores”
t0“Zea mays”
Claim · model-written summary
RN frequency at knobs was similar to or above average SC frequency.
- Outcome
- frequency of RNs at knobse0
- Direction
- similar to or highere0
- Comparator
- average frequency of RNs along the SCse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The frequency of RNs at knobs is either similar to or higher than the average frequency of RNs along the SCs”
t0“Zea mays”