The pattern of polytene chromosome conjugation and crossing-over in interspecific hybrids of Drosophila

1971 ◽  
Vol 41 (6) ◽  
pp. 249-254 ◽  
Author(s):  
M. B. Evgenev
Keyword(s):  
Polytene Chromosome ◽  
Interspecific Hybrids ◽  
Crossing Over ◽  
Chromosome Conjugation

CYTOLOGY OF A GENETIC SEXING SYSTEM IN ANOPHELES ALBIMANUS

1979 ◽  
Vol 21 (2) ◽  
pp. 201-211 ◽  
Author(s):  
P. E. Kaiser ◽  
J. A. Seawright ◽  
D. J. Joslyn
Keyword(s):  
Gamma Irradiation ◽  
Polytene Chromosome ◽  
Physical Distance ◽  
Crossing Over ◽  
Resistance Allele ◽  
Anopheles Albimanus ◽  
Genetic Sexing ◽  
Physical Size ◽  
Chromosome Inversions ◽  
Chromosome Arm

Several translocation and translocation-inversion strains were induced in Anopheles albimanus Wiedemann by using X and gamma irradiation. The propoxur resistance allele (prr), located on chromosome arm 2R, was used to screen for T(Y;2R) translocations and In(2R) inversions. Six T(Y;2R) translocations and eight In(2R) inversions are described herein. The strains designated In(2R)[T(Y:2R)3]2 and In(2R)[T(Y;2R)6]4 eliminated 99.8% and 99.7%, respectvely, of the crossing over between the translocation breakpoint and the prr locus. A direct correlation is shown between genetic map units and physical distance (micrometers) of the polytene chromosome. Inversions are shown to eliminate recombinants in excess of the expected value based on physical size of the aberration. The Y chromosome, which is heterochromatic and located in the chromocenter in polytene complements, is visible in two terminal translocations.

scholarly journals THE CYTOGENETIC STUDY OF CROSSING OVER IN INTERSPECIFIC HYBRIDS BETWEEN DROSOPHILA VIRILIS AND D. TEXANA

Genetics ◽  
1976 ◽  
Vol 83 (2) ◽  
pp. 355-360
Author(s):  
M B Evgen'ev
Keyword(s):  
Interspecific Hybrids ◽  
Cytogenetic Study ◽  
Genetic Exchange ◽  
Drosophila Virilis ◽  
Crossing Over ◽  
Main Criterion ◽  
Heterozygous Condition ◽  
Series Of Experiments ◽  
Single Cluster

ABSTRACT Spontaneous crossing over was studied by means of combined cytological and genetic methods in F1  Drosophila virilis x D. texanafemales (series I) and in D. virilis females carrying a D. texana fifth chromosome in heterozygous condition (series II). The main criterion utilized to distinguish the oogonial crossovers from the meiotic ones is the identity of cytological positions of genetic exchange in crossovers constituting a cluster. Five clusters of crossovers with identical positions of exchange were found in the first series of experiments. In the second series of experiments not a single cluster of crossovers resulting from oogonial crossing over was found.

A cytological study of two closely related blackfly species: Cnephia dacotensis and Cnephia ornithophilia (Diptera: Simuliidae)

1975 ◽  
Vol 53 (11) ◽  
pp. 1622-1637 ◽  
Author(s):  
William S. Procunier
Keyword(s):  
Light Microscopy ◽  
Polytene Chromosome ◽  
Sex Chromosomes ◽  
Cytological Study ◽  
Molecular Model ◽  
Crossing Over ◽  
X Chromosomes ◽  
Synaptonemal Complexes ◽  
Y Chromosomes

Cnephia dacotensis and C. ornithophilia are two closely related blackfly species. Their polytene chromosome complements differ in three interspecific inversions, in separate inversion polymorphisms, and the presence of specific sex chromosomes of C. dacotensis. These sex chromosomes comprise four structurally different X chromosomes and two structurally different Y chromosomes. A molecular model is proposed for their evolution. Light microscopy revealed that both species have male achiasmate meiosis. Male larvae of C. dacotensis lack synaptonemal complexes. Random association of inversions IIIS-1 and IIIL-1 and the presence of synaptonemal complexes indicate that crossing-over occurs in the female.

MEIOTIC BEHAVIOR OF EXTRA HETEROCHROMATIN IN THE TOMATO: EFFECTS ON SEVERAL VITAL PROCESSES

1976 ◽  
Vol 18 (2) ◽  
pp. 325-337 ◽  
Author(s):  
Carlos F. Quirós
Keyword(s):  
Chromosome Pairing ◽  
Meiotic Prophase ◽  
Interspecific Hybrids ◽  
Constitutive Heterochromatin ◽  
Nucleolar Organizer ◽  
Crossing Over ◽  
Meiotic Behavior ◽  
Tomato Genome ◽  
Leaf Necrosis ◽  
Ectopic Pairing

The cytological behavior during meiosis of extra constitutive heterochromatin and the effects of such additions to the tomato genome were investigated. The main source of extra heterochromatin was 2S∙2S, a completely heterochromatic isochromosome carrying a nucleolar organizer in each of its arms. Meiotic behavior of a half-heterochromatic, tertiary chromosome 5L∙2S in the presence of 2S∙2S was studied. Wehn 2S∙2S chromosomes were present in more than two doses, achiasmatic simultaneous pairing of three, four and five arms of these chromosomes was observed. "Ectopic" pairing of 2S∙2S with heterochromatin of nonhomologous chromosomes was also observed. It is postulated that "ectopic" pairing neutralized in part the high percentage of anaphase I equational division of the 2S∙2S chromosomes. In some individuals the 2S∙2S chromosome was found organizing an extra, smaller-than-normal nucleolus during meiotic prophase. Conspicuous nucleolar vacuoles were also observed in the progenies of plants carrying 2S∙2S extra chromosomes. It was found that the 2S∙2S chromosome alters diakinesis association and segregation of the 5L∙7S chromosome when both are in the same cell. 2S∙2S chromosomes reduced chiasma frequency, which was also accompanied by reduction of crossing-over for some of the tested gene intervals when 2S∙2S was present in one dose. No effects of 2S∙2S on chromosome pairing of interspecific hybrids were detected. Another effect produced by the addition of 2S∙2S chromosomes was expressed as leaf necrosis in some individuals.

Crossing over with Ruben Blades

1991 ◽  
Vol 44 (2) ◽  
pp. 301-323 ◽  
Author(s):  
Don Michael Randel
Keyword(s):  
Crossing Over ◽  
Ruben Blades
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