Abstract
A class of tandemly repeated DNA sequences (TR-1) of 350-bp unit length was isolated from the knob DNA of chromosome 9 of Zea mays L. Comparative fluorescence in situ hybridization revealed that TR-1 elements are also present in cytologically detectable knobs on other maize chromosomes in different proportions relative to the previously described 180-bp repeats. At least one knob on chromosome 4 is composed predominantly of the TR-1 repeat. In addition, several small clusters of the TR-1 and 180-bp repeats have been found in different chromosomes, some not located in obvious knob heterochromatin. Variation in restriction fragment fingerprints and copy number of the TR-1 elements was found among maize lines and among maize chromosomes. TR-1 tandem arrays up to 70 kilobases in length can be interspersed with stretches of 180-bp tandem repeat arrays. DNA sequence analysis and restriction mapping of one particular stretch of tandemly arranged TR-1 units indicate that these elements may be organized in the form of fold-back DNA segments. The TR-1 repeat shares two short segments of homology with the 180-bp repeat. The longest of these segments (31 bp; 64% identity) corresponds to the conserved region among 180-bp repeats. The polymorphism and complex structure of knob DNA suggest that, similar to the fold-back DNA-containing giant transposons in Drosophila, maize knob DNA may have some properties of transposable elements.
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Claims 7
Claim · model-written summary
TR-1 is a 350-bp tandem repeat isolated from maize chromosome 9 knob DNA.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A class of tandemly repeated DNA sequences (TR-1) of 350-bp unit length was isolated from the knob DNA of chromosome 9 of Zea mays L.”
Claim · model-written summary
TR-1 elements occur in knobs on other maize chromosomes in different proportions relative to 180-bp repeats.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“TR-1 elements are also present in cytologically detectable knobs on other maize chromosomes in different proportions relative to the previously described 180-bp repeats”
Claim · model-written summary
At least one chromosome 4 knob is predominantly TR-1 repeat.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At least one knob on chromosome 4 is composed predominantly of the TR-1 repeat”
e1“other maize chromosomes”
Claim · model-written summary
Small TR-1 and 180-bp repeat clusters occur on different chromosomes, some outside obvious knob heterochromatin.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“several small clusters of the TR-1 and 180-bp repeats have been found in different chromosomes, some not located in obvious knob heterochromatin”
e1“other maize chromosomes”
Claim · model-written summary
TR-1 restriction fragment fingerprints and copy number vary among maize lines and chromosomes.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Variation in restriction fragment fingerprints and copy number of the TR-1 elements was found among maize lines and among maize chromosomes”
Claim · model-written summary
TR-1 arrays up to 70 kilobases long can be interspersed with 180-bp tandem repeat arrays.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“TR-1 tandem arrays up to 70 kilobases in length can be interspersed with stretches of 180-bp tandem repeat arrays”
e1“other maize chromosomes”
Claim · model-written summary
TR-1 shares two short homology segments with the 180-bp repeat.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The TR-1 repeat shares two short segments of homology with the 180-bp repeat”
e1“other maize chromosomes”