scholarly journals INCIPIENT GENOME DIFFERENTIATION IN GOSSYPIUM. I. CHROMOSOMES 14, 15, 16, 19 AND 20 ASSESSED IN G. HIRSUTUM, G. RAIMONDII AND G. LOBATUM BY MEANS OF SEVEN A-D TRANSLOCATIONS

Genetics ◽  
1978 ◽  
Vol 90 (1) ◽  
pp. 133-149
Author(s):  
Margaret Y Menzel ◽  
Meta S Brown ◽  
Safia Naqi
Keyword(s):  
Genetic Control ◽  
Crossing Over ◽  
Early Stages ◽  
Genome Differentiation ◽  
Reciprocal Exchange ◽  
Whole Genomes ◽  
Genome Divergence ◽  
Chromosome Regions

ABSTRACT The genus Gossypium is favorable for study of genome divergence at several levels. Early stages of divergence have been studied among four D genomes by comparing chiasma frequencies (reciprocal exchanges) between pairs of genomes and between individual counterpart chromosomes marked by heterozygous translocations. D5 (G. raimondii) shows barely detectable differentiation from from Dh (G. hirsutum), whereas D7 (G. lobatum) is considerably less closely related to Dh than is D5. Fragmentary data suggest that D2-2 (G. harknessii) falls between D5 and D7 in its relationship to Dh. Since chiasma frequencies in individual chromosomes and marked regions exhibit the same order of relationships as their corresponding whole genomes, it is concluded that the genome differentiation is generalized (i.e., nucleus-wide) rather than localized in specific chromosomes or chromosome regions. Estimates of relationships based on reciprocal exchange frequencies agree with those based upon preferential synapsis in allohexaploids reported previously. Since preferential synapsis and reciprocal exchange frequencies reveal the same order of relationships, it is concluded that to some extent they reflect common underlying changes in chromosome properties, despite recent evidence that synapsis and crossing over are under independent genetic control.

scholarly journals INDUCTION OF INTRACHROMOSOMAL RECOMBINATION IN YEAST BY INHIBITION OF THYMIDYLATE BIOSYNTHESIS

Genetics ◽  
1986 ◽  
Vol 114 (2) ◽  
pp. 375-392
Author(s):  
B A Kunz ◽  
G R Taylor ◽  
R H Haynes
Keyword(s):  
Gene Conversion ◽  
Dna Sequences ◽  
Dna Hybridization ◽  
Crossing Over ◽  
Repeated Dna ◽  
Yeast Saccharomyces Cerevisiae ◽  
Haploid Strain ◽  
Reciprocal Exchange ◽  
Coli Plasmid ◽  
Antifolate Drugs

ABSTRACT The biosynthesis of thymidylate in the yeast Saccharomyces cerevisiae can be inhibited by antifolate drugs. We have found that antifolate treatment enhances the formation of leucine prototrophs in a haploid strain of yeast carrying, on the same chromosome, two different mutant leu2 alleles separated by Escherichia coli plasmid sequences. That this effect is a consequence of thymine nucleotide depletion was verified by the finding that provision of exogenous thymidylate eliminates the increased production of Leu+ colonies. DNA hybridization analysis revealed that recombination, including reciprocal exchange, gene conversion and unequal sister-chromatid crossing over, between the duplicated genes gave rise to the induced Leu+ segregants. Although gene conversion unaccompanied by crossing over was responsible for the major fraction of leucine prototrophs, events involving reciprocal exchange exhibited the largest increase in frequency. These data show that recombination is induced between directly repeated DNA sequences under conditions of thymine nucleotide depletion. In addition, the results of this and previous studies are consistent with the possibility that inhibition of thymidylate biosynthesis in yeast may create a metabolic condition that provokes all forms of mitotic recombination.

The genetics of the mimetic butterfly Papilio memnon L

1968 ◽  
Vol 254 (791) ◽  
pp. 37-89 ◽  
Keyword(s):  
Genetic Control ◽  
Crossing Over ◽  
Supporting Evidence ◽  
South East Asia ◽  
Dominance Relationships ◽  
Sympatric Forms ◽  
Occasional Occurrence ◽  
Wing Patterns ◽  
Industrial Melanism ◽  
Complex Locus

Papilio memnon is a swallowtail butterfly widely distributed in south-east Asia. The females are highly polymorphic and many of them are mimetic. The mode of inheritance of seventeen of the female forms is reported. In contradistinction to earlier work it has been shown that they are controlled by what appears to be a series of at least eleven autosomal alleles at one locus, sexcontrolled to the female in effect. There is evidence, however, that the locus is complex, comprising at least three closely linked loci with occasional occurrence of crossing over between them. Two characters which are not polymorphic and one which may be polymorphic are controlled by genes unlinked to the complex locus (the super-gene). In general, dominance is complete between sympatric forms but absent when they are allopatric. The resemblance between the mimetic forms of P. memnon and their models is greater in the genecomplex of a race in which the allelomorph occurs than in hybrids with a race in which it does not. Thus in no case is the resemblance better in the race cross, in ten cases there is no change and in thirty-five the mimicry is less good. The genetic control of the polymorphism in P. memnon shows remarkable parallels with that in P. dardanus and provides further supporting evidence for Fisher’s and Ford’s view that mimicry evolved gradually by adjustment of the gene-complex as a result of natural selection favouring those wing patterns which most closely resembled the models. Furthermore, as in P. dardanus, the mimicry is controlled by what appears to be a super-gene, adding weight to the conclusion that the genetic control of the polymorphic Batesian mimicry has evolved gradually by the accumulation of closely linked allelomorphs in advantageous combinations. This contrasts with the genetic control of Mullerian mimicry as evidenced in the Heliconids. In P. memnon the dominance relationships of the monomorphic tailed and tailless condition (excluding the form achates ) indicate that dominance can be evolved even when the characters concerned are not polymorphic. In addition, the lower frequency of dominance between allopatric forms than between sympatric ones is strongly in favour of the view that dominance has evolved. Similar evidence has been found from breeding work in the Heliconids and in P. dardanus ; however, the phenomenon is not confined to mimetic situations since there is also evidence for the evolution of dominance in other polymorphisms including industrial melanism.

CHARACTERIZATION OF HUMAN CHROMOSOMAL CONSTITUTIVE HETEROCHROMATIN

2020 ◽  
Vol 53 (02) ◽  
pp. 08-11
Author(s):  
Aytakin Hasanova
Keyword(s):  
Satellite Dna ◽  
Constitutive Heterochromatin ◽  
Chromosome Breakage ◽  
Centromeric Heterochromatin ◽  
Crossing Over ◽  
Alpha Satellite ◽  
Alpha Satellite Dna ◽  
Chromosome Regions ◽  
Chromosome Disjunction

Heterochromatin of centromeric chromosome regions contains late replicating, largely repetitive DNA. It is suggested that heterochromatin participates in chromosome pairing, crossing-over and in chromosome disjunction control (1,3). Centromeric heterochromatin, a variety of heterochromatin, is a tightly packed form of DNA.Centromeric heterochromatin is a constituent in the formation ofactive centromeres in most higher-order organisms; the domain exists on both mitotic and interphase chromosomes. (4,5,6,8) Centromeric heterochromatin is usually formed on alpha satellite DNA in humans; however, there have been cases where centric heterochromatin and centromeres have formed on originally euchromatin domains lacking alpha satellite DNA; this usually happens as a result of a chromosome breakage event and the formed centromere is called a neocentromere.

PARACENTRIC INVERSIONS AND DETECTION OF SEX LINKED RECESSIVE LETHALS IN AEDES AEGYPTI

1970 ◽  
Vol 12 (3) ◽  
pp. 635-650 ◽  
Author(s):  
Satish C. Bhalla
Keyword(s):  
Aedes Aegypti ◽  
Genetic Control ◽  
Chromosomal Aberrations ◽  
The Other ◽  
Crossing Over ◽  
Partial Sterility ◽  
X Irradiation ◽  
Paracentric Inversions

Two sex linked paracentric inversions one on m chromosome, marked with bz (bronze body) and the other on M chromosome, marked with w (white eye), were artificially induced with X-irradiation and isolated. The inversions are designated as In. (1)1 and In. (1)2 respectively. The former is more than 23 units long and the later more than 16 units. Both suppress crossing over markedly and are associated with partial sterility. The two inversions are utilized as crossover suppressors in a technique designed for detecting sex linked recessive lethals. The technique works satisfactorily with certain limitations. The possibility of combining inversions with other chromosomal aberrations for genetic control of Aedes aegypti populations is suggested.

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.

scholarly journals SOMATIC CROSSING OVER AND ITS GENETIC CONTROL IN DROSOPHILA

Genetics ◽  
1960 ◽  
Vol 45 (3) ◽  
pp. 345-357
Author(s):  
Ellen C Weaver
Keyword(s):  
Genetic Control ◽  
Crossing Over

Recombinationless meiosis in Saccharomyces cerevisiae

1981 ◽  
Vol 1 (10) ◽  
pp. 891-901
Author(s):  
R E Malone ◽  
R E Esposito
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
Genetic Control ◽  
Meiotic Recombination ◽  
Meiotic Division ◽  
Crossing Over ◽  
Background Levels ◽  
Recombination System ◽  
Rad50 Gene ◽  
Meiosis I

We have utilized the single equational meiotic division conferred by the spo13-1 mutation of Saccharomyces cerevisiae (S. Klapholtz and R. E. Esposito, Genetics 96:589-611, 1980) as a technique to study the genetic control of meiotic recombination and to analyze the meiotic effects of several radiation-sensitive mutations (rad6-1, rad50-1, and rad52-1) which have been reported to reduce meiotic recombination (Game et al., Genetics 94:51-68, 1980); Prakash et al., Genetics 94:31-50, 1980). The spo13-1 mutation eliminates the meiosis I reductional segregation, but does not significantly affect other meiotic events (including recombination). Because of the unique meiosis it confers, the spo13-1 mutation provides an opportunity to recover viable meiotic products in a Rec- background. In contrast to the single rad50-1 mutant, we found that the double rad50-1 spo13-1 mutant produced viable ascospores after meiosis and sporulation. These spores were nonrecombinant: meiotic crossing-over was reduced at least 150-fold, and no increase in meiotic gene conversion was observed over mitotic background levels. The rad50-1 mutation did not, however, confer a Rec- phenotype in mitosis; rather, it increased both spontaneous crossing-over and gene conversion. The spore inviability conferred by the single rad6-1 and rad52-1 mutations was not eliminated by the presence of the spo13-1 mutation. Thus, only the rad50 gene has been unambiguously identified by analysis of viable meiotic ascospores as a component of the meiotic recombination system.

INCOMPLETE CONCURRENCE OF EVIDENCE FROM PROTEIN ELECTROPHORESIS AND GENOME ANALYSIS REGARDING THE ORIGIN OF AEGILOPS OVATA

1975 ◽  
Vol 17 (1) ◽  
pp. 1-8 ◽  
Author(s):  
J. Giles Waines ◽  
B. Lennart Johnson
Keyword(s):  
Genetic Control ◽  
Chromosome Pairing ◽  
Genome Analysis ◽  
Diploid Species ◽  
Introgressive Hybridization ◽  
Seed Proteins ◽  
Protein Electrophoresis ◽  
Water Soluble ◽  
Genome Divergence

Electrophoresis of ethanol extracted, water soluble, seed proteins of many different biotypes of 3 diploid species of Aegilops and of the tetraploid A. ovata L. suggest that A. ovata may be descended from an allotetraploid of A. umbellulata Zhuk. and A. squarrosa L. This does not agree with the few published results of genome analysis, which suggest that A. umbellulata and A. comosa Sibth. &Smith are the ancestors of A. ovata. Hypotheses advanced to explain this incomplete concurrence of evidence from these two biosystematic methods include an insufficiency of samples, genome divergence, translocations followed by introgressive hybridization and genetic control of meitoic chromosome pairing.

scholarly journals DNA repair and crossing over favor similar chromosome regions as discovered in radiation hybrid of Triticum

BMC Genomics ◽  
2012 ◽  
Vol 13 (1) ◽  
pp. 339 ◽  
Author(s):  
Ajay Kumar ◽  
Filippo M Bassi ◽  
Etienne Paux ◽  
Omar Al-Azzam ◽  
Monika de Jimenez ◽  
...  
Keyword(s):  
Dna Repair ◽  
Radiation Hybrid ◽  
Crossing Over ◽  
Chromosome Regions

ON THE CONTROL OF THE DISTRIBUTION OF MEIOTIC EXCHANGE IN DROSOPHILA MELANOGASTER

Genetics ◽  
1982 ◽  
Vol 101 (1) ◽  
pp. 81-89
Author(s):  
Adelaide T C Carpenter ◽  
Bruce S Baker
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Control ◽  
Low Frequency ◽  
Minor Component ◽  
Crossing Over ◽  
Meiotic Mutants ◽  
A Minor

ABSTRACT The effects of eight recombination-defective meiotic mutants on crossing over within the X heterochromatin were examined. Since none permit substantial frequencies of exchange within heterochromatin although six lessen or abolish constraints on the location of exchanges within euchromatin, the systems that prohibit exchange within heterochromatin and that govern where exchanges will occur in euchromatin are under separate genetic control.—A minor component of the effects of mei-218 is the production of nonhomologous exchanges; of mei-9 is the recovery of deleted chromatids; and of mei-41 is the recovery of deleted chromatids and/or a low frequency of heterochromatic exchanges.

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