Inversion
Duplications
Epidemiology and
Etiology:
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Interstitial inverted duplication with associated terminal
deletion
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A chromosome carries a
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During meiosis:
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formation of a dicentric chromosome
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subsequently breaks (during meiosis)
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forms a monocentric duplicated and
deleted chromosome
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3 proposed mechanisms:
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Gorinati et al.
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Paracentric inversion in one
of the parents (0.1% to 0.5% of the population)
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During meiosis:
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Inversion loop is formed between the chromosome carrying the paracentric inversion and its normal homologue
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Cross-over event within the loop produces:
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A dicentric chromosome
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An acentric fragment
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Pre-zygotic breakage of the dicentric
outside the inverted region produces:
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A monocentric chromosome with a
terminal deletion and an inverted duplication with a single copy region (the
region that was inverted) between the duplication
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Inverted LCRs on homologous chromosomes or on the same chromosome
arm
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Partial folding of one homologue onto itself
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Recombination event between the inverted repeats
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Resulting dicentric chromosome and an acentric fragment
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Prezygotic breakage of the dicentric outside the inverted repeats
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A monocentric chromosome with a terminal
deletion and an inverted duplication with a single copy region (the region
between the 2 repeats) between the duplication
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Initial double-strand break of the 2 sister chromatids
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U-type reunion between sister chromatids
OR U-type exchange with unbroken homologous chromosome produces a dicentric chromosome
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Dicentric chromosome
undergoes random breakage distal to the fusion site
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Prezygotic breakage of the dicentric outside the fusion region produces:
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A monocentric chromosome with a
terminal deletion and an inverted duplication with NO single copy region
between the duplication
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Rowe et al. demonstrate that this is the most common mechanism
for sites other than 8p and perhaps 15q
Common sites:
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8p most common site for inverted duplication with a terminal deletion
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Has been described for:
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1p
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1q
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2p
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2q
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3p
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4p
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4q
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5p
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7q
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8p
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9p
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9q
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10p
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10q
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11p
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14q
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15q
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17p
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18q
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21q
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Xp
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Variety of ring chromosomes
Gross features:
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Histologic
features:
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Immunophenotype:
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Marker: |
Sensitivity: |
Specificity: |
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Molecular features:
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Other features:
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References:
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Rowe LR, Lee J, Rector L, et al. U-type exchange is the most
frequent mechanism for inverted duplication with terminal deletion
rearrangements. J. Med. Genet. 2009. Available at: http://www.ncbi.nlm.nih.gov.myaccess.library.utoronto.ca/pubmed/19293169
[Accessed June 4, 2009].