Cytological and molecular analysis of centromere misdivision in maize

Genome ◽  
2002 ◽  
Vol 45 (4) ◽  
pp. 759-768 ◽  
Author(s):  
Étienne Kaszás ◽  
Akio Kato ◽  
James A Birchler
Keyword(s):  
Ring Chromosome ◽  
B Chromosome ◽  
Repeat Sequence ◽  
Telomeric Repeat ◽  
Univalent Chromosome ◽  
Telocentric Chromosome ◽  
Chromosome Healing ◽  
Centromeric Repeat ◽  
Ring Chromosomes ◽  
Pulsed Field Electrophoresis

B chromosome derivatives suffering from breaks within their centromere were examined cytologically and molecularly. We showed by high resolution FISH that misdivision of the centromere of a univalent chromosome can occur during meiosis. The breaks divide the centromere repeat sequence cluster. A telocentric chromosome formed by misdivision was found to have the addition of telomeric repeats to the broken centromere. A ring chromosome formed after misdivision occurred by fusion of the broken centromere to the telomere. Pulsed-field electrophoresis analyses were performed on the telocentric and ring chromosomes to identify fragments that hybridize to both the telomeric repeat and the B-specific centromeric repeat. We conclude that healing of broken maize centromeres can be achieved through the mechanisms of addition or fusion of telomeric repeat sequences to the broken centromere.Key words: centromere, telomere, meiosis, chromosome healing, B chromosome, Zea mays.

Identification of a family of repeated sequences on the rye B chromosome

Genome ◽  
1990 ◽  
Vol 33 (6) ◽  
pp. 908-913 ◽  
Author(s):  
Michael J. Sandery ◽  
John W. Forster ◽  
Richard Blunden ◽  
R. Neil Jones
Keyword(s):  
Secale Cereale ◽  
Direct Evidence ◽  
B Chromosome ◽  
Repeat Sequence ◽  
B Chromosomes ◽  
Repeated Sequences ◽  
Significant Heterogeneity ◽  
Origin And Evolution ◽  
The Family

A novel family of highly repeated sequences on the B chromosome of rye (Secale cereale) has been identified. The D1100 family has not been detected on the rye A chromosomes and shows little or no homology to any previously described repeat sequence in rye. In addition, different rye species, and different B chromosomes within the same species, show significant heterogeneity in the arrangement of the D1100 sequences. An EcoRI clone of a member of the family has been obtained. These results provide direct evidence for the organisation and nature of the B-chromosome DNA in rye, and they are discussed in relation to the origin and evolution of rye B chromosomes.Key words: B chromosome, Secale cereale, repeated sequences.

scholarly journals Human Ring Chromosomes – New Insights for their Clinical Significance

2013 ◽  
Vol 16 (1) ◽  
pp. 13-19 ◽  
Author(s):  
R.S. Guilherme ◽  
E Klein ◽  
A.B. Hamid ◽  
S Bhatt ◽  
M Volleth ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Clinical Signs ◽  
Ring Chromosome ◽  
Signs And Symptoms ◽  
Molecular Techniques ◽  
Ring Chromosomes ◽  
Multicolor Banding ◽  
Clinical Signs And Symptoms ◽  
Clinical Problems

Abstract Twenty-nine as yet unreported ring chromosomes were characterized in detail by cytogenetic and molecular techniques. For FISH (fluorescence in situ hybridization) previously published high resolution approaches such as multicolor banding (MCB), subcentromere-specific multi-color-FISH (cenM-FISH) and two to three-color-FISH applying locus-specific probes were used. Overall, ring chromosome derived from chromosomes 4 (one case), 10 (one case), 13 (five cases), 14, (three cases), 18 (two cases), 21 (eight cases), 22 (three cases), X (five cases) and Y (one case) were studied. Eight cases were detected prenatally, eight due developmental delay and dysmorphic signs, and nine in connection with infertility and/or Turner syndrome. In general, this report together with data from the literature, supports the idea that ring chromosome patients fall into two groups: group one with (severe) clinical signs and symptoms due to the ring chromosome and group two with no obvious clinical problems apart from infertility.

A RING CHROMOSOME IN AN F1 HYBRID BETWEEN WHEAT AND AGROPYRON

1959 ◽  
Vol 37 (6) ◽  
pp. 1271-1276 ◽  
Author(s):  
Koichiro Tsunewaki
Keyword(s):  
Ring Chromosome ◽  
Root Tip ◽  
Root Tips ◽  
F1 Hybrid ◽  
Ring Chromosomes ◽  
Differential Elimination ◽  
Tip Cells ◽  
Root Tip Cells ◽  
Mitotic Behavior

A plant having 41 normal rod-shaped chromosomes and a ring chromosome was found among hexaploid.F1 hybrids from a wheat–Agropyron cross. Cytological investigations were carried out to determine the mitotic behavior of this ring chromosome.The investigations revealed that most of the possible products of the breakage–fusion–bridge cycle known to occur in a ring chromosome were present in root tip cells. The fact that a rod-shaped chromosome is not derived from a ring chromosome in the cycle was confirmed, because no metaphase cells examined had 42 or more rod-shaped chromosomes.About 80% of the ring chromosomes were eliminated from the root tips of the seedling after 26 days. The size of the ring chromosome did not appear to influence the rate of elimination. The polyploid nature of the plant may account for the rapid, non-differential elimination of this chromosome.

scholarly journals Sequential de novo centromere formation and inactivation on a chromosomal fragment in maize

2015 ◽  
Vol 112 (11) ◽  
pp. E1263-E1271 ◽  
Author(s):  
Yalin Liu ◽  
Handong Su ◽  
Junling Pang ◽  
Zhi Gao ◽  
Xiu-Jie Wang ◽  
...  
Keyword(s):  
Dna Sequences ◽  
De Novo ◽  
B Chromosome ◽  
Chromosome 9 ◽  
Centromeric Dna ◽  
Repeat Sequences ◽  
Centromeric Repeat ◽  
And Function ◽  
Centromere Assembly ◽  
Derivatives Of

The ability of centromeres to alternate between active and inactive states indicates significant epigenetic aspects controlling centromere assembly and function. In maize (Zea mays), misdivision of the B chromosome centromere on a translocation with the short arm of chromosome 9 (TB-9Sb) can produce many variants with varying centromere sizes and centromeric DNA sequences. In such derivatives of TB-9Sb, we found a de novo centromere on chromosome derivative 3-3, which has no canonical centromeric repeat sequences. This centromere is derived from a 288-kb region on the short arm of chromosome 9, and is 19 megabases (Mb) removed from the translocation breakpoint of chromosome 9 in TB-9Sb. The functional B centromere in progenitor telo2-2 is deleted from derivative 3-3, but some B-repeat sequences remain. The de novo centromere of derivative 3-3 becomes inactive in three further derivatives with new centromeres being formed elsewhere on each chromosome. Our results suggest that de novo centromere initiation is quite common and can persist on chromosomal fragments without a canonical centromere. However, we hypothesize that when de novo centromeres are initiated in opposition to a larger normal centromere, they are cleared from the chromosome by inactivation, thus maintaining karyotype integrity.

scholarly journals Ring Chromosome 20 Associated with Refractory Epilepsy: A Case Report

2012 ◽  
Vol 2 (3) ◽  
pp. 141-144
Author(s):  
A Radha Rama Devi ◽  
Usha R Dutta
Keyword(s):  
Behavioral Problems ◽  
Refractory Epilepsy ◽  
Ring Chromosome ◽  
Epileptic Seizures ◽  
Dysmorphic Features ◽  
Mild Developmental Delay ◽  
Chromosome 20 ◽  
First Case ◽  
South Indian ◽  
Ring Chromosomes

Ring chromosome 20 is a rare chromosomal abnormality characterized mainly by refractory epileptic seizures, cognitive and behavioral problems, and absence of definite dysmorphic features. We report a 5-year-old boy with refractory epilepsy and minimal dysmorphic features who first presented with mild developmental delay at 11 months of age. The karyotype of the child was 46,XY,r(20)(p13q13.3). Till date there are 69 cases of ring chromosome 20 reported in the literature, including mosaics and supernumerary ring chromosomes. To our knowledge, this is the first case of ring chromosome 20 with refractory epilepsy reported from the south Indian population.DOI: http://dx.doi.org/10.3126/ajms.v2i3.5607Asian Journal of Medical Sciences 2 (2011) 141-144

scholarly journals The yeast telomerase RNA, TLC1, participates in two distinct modes of TLC1-TLC1 association processes in vivo

2015 ◽  
Author(s):  
Tet Matsuguchi ◽  
Elizabeth Blackburn
Keyword(s):  
Nuclear Periphery ◽  
Repeat Sequence ◽  
Telomeric Repeat ◽  
G1 Phase ◽  
Telomerase Rna ◽  
Reverse Transcriptase Domain ◽  
Core Enzyme ◽  
Yeast Telomerase ◽  
Enzymatic Activation

Telomerase core enzyme minimally consists of the telomerase reverse transcriptase domain-containing protein (Est2 in budding yeast S. cerevisiae) and telomerase RNA, which contains the template specifying the telomeric repeat sequence synthesized. Here we report that in vivo, a fraction of S. cerevisiae telomerase RNA (TLC1) molecules form complexes containing at least two molecules of TLC1, via two separable modes: one requiring a sequence in the 3’ region of the immature TLC1 precursor and the other requiring Ku and Sir4. Such physical TLC1-TLC1 association peaked in G1 phase and did not require telomere silencing, telomere tethering to the nuclear periphery, telomerase holoenzyme assembly, or detectable Est2-Est2 protein association. These data indicate that TLC1-TLC1 associations reflect processes occurring during telomerase biogenesis; we propose that TLC1-TLC1 associations and subsequent reorganization may be regulatory steps in telomerase enzymatic activation.

Autosomal Ring Chromosomes

2018 ◽  
Author(s):  
R. J McKinlay Gardner ◽  
David J Amor
Keyword(s):  
Ring Chromosome ◽  
Chromosome Count ◽  
Small Ring ◽  
Intellectual Deficiency ◽  
Relevant Issue ◽  
Ring Chromosomes ◽  
Phenotypic Abnormality ◽  
Genetic Risks ◽  
Additional Chromosome ◽  
End To End

Ring chromosomes are uncommon. The typical physical phenotype comprises major dysmorphogenesis and intellectual deficiency, and reproduction is not usually a relevant issue. A ring chromosome is formed due to an end-to-end fusion of chromosome tips. Almost always, the end result is an imbalance and significant phenotypic abnormality. Rarely, however, this is not the case. In this chapter, genetic risks for ring carriers for whom procreation is a realistic likelihood are considered. This chapter distinguishes between those with a normal 46 chromosome count, one being a ring, and those with a 47 chromosome count, the additional chromosome being a (necessarily small) ring.

Prenatal diagnosis of ring chromosome 13: a rare chromosomal aberration

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Haruka Goto ◽  
Yasuyuki Fujita ◽  
Yuka Sato ◽  
Saki Kido ◽  
Masanobu Ogawa ◽  
...  
Keyword(s):  
Chromosomal Aberration ◽  
Good Condition ◽  
Ring Chromosome ◽  
Japanese Woman ◽  
Trisomy 13 ◽  
Fish Analysis ◽  
Chromosome 13 ◽  
Ring Chromosomes ◽  
Banding Analysis ◽  
Female Baby

Abstract We report the case of a 24-year-old Japanese woman, gravida 2, para 1, who became pregnant spontaneously. At 24 weeks of gestation, her fetus was found to have various abnormalities, including holoprosencephaly, congenital heart disease and severe fetal growth restriction, and she was referred to our hospital. From these findings, the fetus was suspected of having a chromosomal aberration, in particular, trisomy 13, and after genetic counseling, amniocentesis for chromosomal analysis was performed. Although the results of fluorescent in situ hybridization (FISH) analysis showed no numeric abnormalities, G-banding analysis revealed a ring chromosome 13; 46, XX, r (13) (p13q32). At 41 weeks of gestation, she delivered a female baby weighing 2240 g with good condition. The respiratory status of the neonate was stable, and she was discharged 30 days after birth. Ring chromosomes are rare chromosomal aberrations, and obstetricians should recognize that ring chromosomes cannot be detected solely by FISH analysis and require G-banding analysis and that information on the ring breakpoint is needed to counsel the parents regarding the fetal and neonatal prognosis.

Unstable inheritance of maize B-type chromosomes that lack centric heterochromatin

Genome ◽  
2006 ◽  
Vol 49 (5) ◽  
pp. 420-431 ◽  
Author(s):  
Wayne R Carlson
Keyword(s):  
B Chromosome ◽  
Chromosome 9 ◽  
Pollen Mitosis ◽  
Genetic Studies ◽  
Telocentric Chromosome ◽  
Deletion Derivative ◽  
Translocation Heterozygote ◽  
Second Pollen Mitosis

The B chromosome of maize undergoes frequent non-disjunction at the second pollen mitosis. In B–A translocations, the B–A chromosome retains the capacity for non-disjunction. We have collected deletion-derivative TB-9Sb stocks. One derivative, the "type 1 telocentric", has a B–9 chromosome that lacks centric heterochromatin. It produces few recessive (non-disjunctional) phenotypes in pollen parent testcrosses of the translocation heterozygote, 9 9–B telo B–9. The finding helped demonstrate the role of centric heterochromatin in non-disjunction. An isochromo some derivative of the type 1 telocentric was also recovered. It was tested in the 9–B 9–B iso B–9 constitution. This is equivalent to 9 9–B telo B–9 in terms of chromosome 9 dosage. Surprisingly, crosses with the isochromosome gave significant levels of recessive phenotypes. In addition, high levels of variegated phenotypes were found. Recently, a circumstance was found that makes inheritance of the type 1 telocentric chromosome somewhat similar to that of the isochromosome. Crosses with hypoploid 9–B 9–B telo B–9 plants showed significant levels of recessive and variegated phenotypes. These crosses were investigated to help explain the source(s) of the phenotypes. Cytological and genetic studies were performed. Centric misdivision was found to account for the variegated phenotypes. A mixture of conventional B non-disjunction and centric misdivision produced the recessive phenotypes. The significance of conventional non-disjunction in the absence of centric heterochromatin is discussed.Key words: cytogenetics, B chromosome, centromere, maize.

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