scholarly journals THE INTERACTION OF KNOBS AND B CHROMOSOMES OF MAIZE IN DETERMINING THE LEVEL OF RECOMBINATION

Genetics ◽  
1974 ◽  
Vol 77 (1) ◽  
pp. 45-54
Author(s):  
C C Chang ◽  
Gary Y Kikudome
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Chromosome 9 ◽  
Crossing Over

ABSTRACT Enhancement of recombination by B chromosomes is influenced by the kind of heterochromatic knob present in or near the tested region of the A chramosomes. In homomorphic chromosome 9 bivalents of KS/KS constitution, double exchanges were increased at the expense of singles, but in the K*/Ks heteromorphs there was a gain in both single and double exchanges at the expense of no-exchange tetrads. Modification of the B chromosome enhancement in different knob compounds was observed only in the megasporocytes.—Different frequencies of recombination are found in plants with odd and even numbers of B Chromosomes; this effect is especially striking in the megasporocytes. The modification in recombination produced by an odd or even number of B chromosomes is a function of the interaction of a particular region and the knob constitution. Odd numbers of B chromosomes were more effective than even numbers in causing increased recombination.—It is concluded that heterochromatic knobs and the essentially heterochromatic supernumeraries may interact in the process of crossing over, with the level of recombination determined in part by knob constitution.

Locating a site on the maize B chromosome that controls preferential fertilization

Genome ◽  
2007 ◽  
Vol 50 (6) ◽  
pp. 578-587 ◽  
Author(s):  
Wayne R. Carlson
Keyword(s):  
B Chromosome ◽  
B Chromosomes ◽  
Chromosome 9 ◽  
Chromosome Deletion ◽  
Pollen Mitosis ◽  
Preferential Fertilization ◽  
Second Pollen Mitosis ◽  
A Site ◽  
Derivatives Of

In maize, the B chromosome can undergo nondisjunction at the second pollen mitosis, producing sperm with two B chromosomes and sperm with zero B chromosomes. Preferential fertilization is the ability of the sperm carrying two B chromosomes to transmit more frequently to the embryo of a kernel than the sperm lacking the B chromosome. A translocation involving the B chromosome and chromosome 9, TB-9Sb, has been used to study preferential fertilization. The B-9 chromosome has the same properties of nondisjunction and preferential fertilization as the standard B chromosome. Deletion derivatives of B-9, which lack the centric heterochromatin and possibly some adjacent euchromatin, were tested for their ability to induce preferential fertilization. They were found to lack the capacity for preferential fertilization.

scholarly journals A new property of the maize B chromosome.

Genetics ◽  
1992 ◽  
Vol 131 (1) ◽  
pp. 211-223 ◽  
Author(s):  
W R Carlson ◽  
R R Roseman
Keyword(s):  
Genetic Control ◽  
Sharp Decrease ◽  
Genetic System ◽  
B Chromosome ◽  
B Chromosomes ◽  
Chromosome 9 ◽  
High Frequencies ◽  
Very High Frequencies ◽  
Very High ◽  
Chromosome Regions

Abstract TB-9Sb is a translocation between the B chromosome and chromosome 9 in maize. Certain deletions of B chromatin from the translocation cause a sharp decrease in B-9 transmission compared to the rate for standard TB-9Sb. The deletions remove components of a B chromosome genetic system that serves to suppress meiotic loss in the female. At least two distinct B-chromosome regions suppress meiotic loss: one on the B-9 and one on 9-B. The system operates by stabilizing univalent B-type chromosomes. It allows the univalents to migrate to one pole in meiosis, despite the absence of a pairing partner. The findings reported here are the first evidence for genetic control of meiotic loss by a B chromosome. However, it is proposed that the practice of suppressing meiotic loss is common to the B chromosomes of all species. The need to suppress meiotic loss results from the fact that B chromosomes are frequently unpaired in meiosis and subject to very high frequencies of loss. B chromosomes may utilize one or more of the following methods to suppress meiotic loss: (a) regular migration of univalent B's to one pole in meiosis, (b) enhanced recombination between B chromosomes and (c) mitotic nondisjunction.

CROSSING OVER AND DIPLOID EGG FORMATION IN THE ELONGATE MUTANT OF MAIZE

Genetics ◽  
1975 ◽  
Vol 79 (3) ◽  
pp. 435-450
Author(s):  
P M Nel
Keyword(s):  
Chromosome 9 ◽  
Meiotic Spindle ◽  
Crossing Over ◽  
Chromosome 5 ◽  
Basic Difference ◽  
Egg Formation ◽  
Preferential Segregation ◽  
Centric Region ◽  
Female Values ◽  
Female Flowers

ABSTRACT Rhoades (1941) found recombination in the proximal regions of chromosome 5 to be higher in male than in female flowers. Two explanations were proposed to account for the lower female values, namely: (1) there is a basic difference in rates of crossing over in mega- and microsporocytes, or (2) selective orientation of the chromosome 5 bivalent on the meiotic spindle leads to the preferential segregation of noncrossover chromatids to the basal megaspore. These alternatives have been tested by carrying out a half-tetrad analysis of the diploid eggs produced by plants homozygous for the recessive elongate (el) allele. The A2—Bt crossover values determined from the diploid eggs of elongate plants were much lower than those calculated from haploid sperm of both El el and el el plants. Since male and female flowers should have similar cross-over values if the orientation hypothesis were correct, it was concluded that the amount of crossing over in the A2-Bt region of chromosome 5 is intrinsically higher in male than in female meiocytes. In the analysis of diploid eggs the use of the Bt locus, which marks the centric region of chromosome 5, provided information on the origin of diploid eggs. The genotypic constitution of 425 diploid eggs was ascertained. Of these, 20.4% were Bt bt. They could not be accounted for by failure of the second meiotic division or by replication during the interphase between the two meiotic divisions, but are expected if there is a single division with an equational separation of the centromere regions of chromosome 5. The Bt Bt and bt bt genotypes arise from a disjunctional separation. It is proposed that diploid eggs are produced by an abnormal meiosis in which there is one division with either disjunctional or equational separation. Disjunctional separation is more frequent but the ratio of the two types varies from ear to ear. Recombination in the A2-Bt-Pr region of chromosome 5 was found to be higher in the haploid gametes of elongate homozygotes than in El El and El el plants. On the other hand, crossing over was reduced in the Sh-Bz segment of chromosome 9 in elongate plants, but the adjacent Bz—Wx interval was unaffected.

scholarly journals Repetitive DNA landscape in essential A and supernumerary B chromosomes of Festuca pratensis Huds

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Rahman Ebrahimzadegan ◽  
Andreas Houben ◽  
Ghader Mirzaghaderi
Keyword(s):  
Repetitive Sequences ◽  
Nuclear Genome ◽  
B Chromosome ◽  
B Chromosomes ◽  
Festuca Pratensis ◽  
Ltr Retrotransposons ◽  
Chromosome Identification ◽  
Satellite Repeats ◽  
Low Pass ◽  
Illumina Sequence

AbstractHere, we characterized the basic properties of repetitive sequences in essential A and supernumerary B chromosomes of Festuca pratensis Huds. This was performed by comparative analysis of low-pass Illumina sequence reads of B chromosome lacking (−B) and B chromosome containing (+B) individuals of F. pratensis. 61% of the nuclear genome is composed of repetitive sequences. 43.1% of the genome are transposons of which DNA transposons and retrotransposons made up 2.3% and 40.8%, respectively. LTR retrotransposons are the most abundant mobile elements and contribute to 40.7% of the genome and divided into Ty3-gypsy and Ty1-copia super families with 32.97% and 7.78% of the genome, respectively. Eighteen different satellite repeats were identified making up 3.9% of the genome. Five satellite repeats were used as cytological markers for chromosome identification and genome analysis in the genus Festuca. Four satellite repeats were identified on B chromosomes among which Fp-Sat48 and Fp-Sat253 were specific to the B chromosome of F. pratensis.

scholarly journals Spatial organization of fibroblast and spermatocyte nuclei with different B-chromosome content in Korean field mouse, Apodemus peninsulae (Rodentia, Muridae)

Genome ◽  
2017 ◽  
Vol 60 (10) ◽  
pp. 815-824 ◽  
Author(s):  
Tatyana V. Karamysheva ◽  
Anna A. Torgasheva ◽  
Yaroslav R. Yefremov ◽  
Anton G. Bogomolov ◽  
Thomas Liehr ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Spatial Organization ◽  
Constitutive Heterochromatin ◽  
B Chromosome ◽  
B Chromosomes ◽  
Laser Scanning Microscopy ◽  
Field Mouse ◽  
Apodemus Peninsulae ◽  
Basic Set ◽  
Korean Field Mouse

Korean field mouse (Apodemus peninsulae) shows a wide variation in the number of B chromosomes composed of constitutive heterochromatin. For this reason, it provides a good model to study the influence of the number of centromeres and amount of heterochromatin on spatial organization of interphase nuclei. We analyzed the three-dimensional organization of fibroblast and spermatocyte nuclei of the field mice carrying a different number of B chromosomes using laser scanning microscopy and 3D fluorescence in situ hybridization. We detected a co-localization of the B chromosomes with constitutive heterochromatin of the chromosomes of the basic set. We showed a non-random distribution of B chromosomes in the spermatocyte nuclei. Unpaired B chromosomes showed a tendency to occur in the compartment formed by the unpaired part of the XY bivalent.

scholarly journals B Chromosomes in Populations of Mammals Revisited

Genes ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 487 ◽  
Author(s):  
Mladen Vujošević ◽  
Marija Rajičić ◽  
Jelena Blagojević
Keyword(s):  
Mammalian Species ◽  
B Chromosome ◽  
Molecular Techniques ◽  
B Chromosomes ◽  
General View ◽  
Protein Coding ◽  
Host Parasite Interactions ◽  
Quantitative Characteristics ◽  
Host Parasite

The study of B chromosomes (Bs) started more than a century ago, while their presence in mammals dates since 1965. As the past two decades have seen huge progress in application of molecular techniques, we decided to throw a glance on new data on Bs in mammals and to review them. We listed 85 mammals with Bs that make 1.94% of karyotypically studied species. Contrary to general view, a typical B chromosome in mammals appears both as sub- or metacentric that is the same size as small chromosomes of standard complement. Both karyotypically stable and unstable species possess Bs. The presence of Bs in certain species influences the cell division, the degree of recombination, the development, a number of quantitative characteristics, the host-parasite interactions and their behaviour. There is at least some data on molecular structure of Bs recorded in nearly a quarter of species. Nevertheless, a more detailed molecular composition of Bs presently known for six mammalian species, confirms the presence of protein coding genes, and the transcriptional activity for some of them. Therefore, the idea that Bs are inert is outdated, but the role of Bs is yet to be determined. The maintenance of Bs is obviously not the same for all species, so the current models must be adapted while bearing in mind that Bs are not inactive as it was once thought.

scholarly journals Transmission rate variation among three B chromosome variants in the fish Prochilodus lineatus (Characiformes, Prochilodontidae)

2013 ◽  
Vol 85 (4) ◽  
pp. 1371-1377 ◽  
Author(s):  
MANOLO PENITENTE ◽  
TATIANA A. VOLTOLIN ◽  
JOSE A. SENHORINI ◽  
JEHUD BORTOLOZZI ◽  
FAUSTO FORESTI ◽  
...  
Keyword(s):  
Transmission Rate ◽  
B Chromosome ◽  
B Chromosomes ◽  
Rate Variation ◽  
Parental Line ◽  
Prochilodus Lineatus ◽  
Extinction Process ◽  
Cytogenetic Studies ◽  
Acrocentric Chromosomes ◽  
Interesting System

Cytogenetic studies were developed in Prochilodus lineatus (Valenciennes 1836), describing an interesting system of small supernumerary chromosomes. The purpose of this work is to study the frequency and morphology of B chromosomes in individuals from the parental line and the inheritance patterns of these elements in individuals obtained from controlled crosses in the species P. lineatus. The transmission rate of B chromosomes revealed a kB=0.388 for the acrocentric type, a kB=0.507 for the metacentric type and a kB=0.526 for the submetacentric type. The obtained results raise hypothesis that B-acrocentric chromosomes are involved in an extinction process in this species, while the metacentric and submetacentric supernumerary elements comprises a neutral mechanism and follows a Mendelian transmission rate.

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.

MOSAICISM OF AN ABNORMALLY LONG B CHROMOSOME IN A BOY WITH PHYSICAL AND MENTAL RETARDATION

PEDIATRICS ◽  
1967 ◽  
Vol 39 (1) ◽  
pp. 68-74
Author(s):  
Lillian Y. F. Hsu ◽  
Iris Nemhauser ◽  
Hilda K. Bettmann ◽  
Edna H. Sobel
Keyword(s):  
Mental Retardation ◽  
Short Stature ◽  
Cell Line ◽  
Normal Cell ◽  
B Chromosome ◽  
B Chromosomes ◽  
Normal Cell Line

An 11-year-old boy with short stature, mental retardation, low-set ears, simian creases, unusual dermatoglyphic patterns, and bilateral dysplastic mid-phalanges of the fifth fingers was found to have mosaicism in both leukocyte and fibroblast (skin) cultures. The normal cell-line predominated and the second cell-line contained an abnormally long chromosome B. The autoradiographic studies suggest that the abnormally long chromosome may involve a No. 5 which contains a translocated on inserted segment of an unknown donor autosome. The possible mechanism for the occurrence of this abnormality is discussed. Nine other instances of abnormally long B chromosomes (with lengthened long arm due to translocation) are reviewed and compared.

scholarly journals Evolution of Plant B Chromosome Enriched Sequences

Genes ◽  
2018 ◽  
Vol 9 (10) ◽  
pp. 515 ◽  
Author(s):  
André Marques ◽  
Sonja Klemme ◽  
Andreas Houben
Keyword(s):  
Repetitive Sequences ◽  
B Chromosome ◽  
B Chromosomes ◽  
Dna Elements ◽  
Formation And Evolution ◽  
The Subject ◽  
Chromosome Formation ◽  
The Impact ◽  
Normal Standard ◽  
Shed Light

B chromosomes are supernumerary chromosomes found in addition to the normal standard chromosomes (A chromosomes). B chromosomes are well known to accumulate several distinct types of repeated DNA elements. Although the evolution of B chromosomes has been the subject of numerous studies, the mechanisms of accumulation and evolution of repetitive sequences are not fully understood. Recently, new genomic approaches have shed light on the origin and accumulation of different classes of repetitive sequences in the process of B chromosome formation and evolution. Here we discuss the impact of repetitive sequences accumulation on the evolution of plant B chromosomes.

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