Variation in "Map Distance" in Neurospora crassa

1969 ◽  
Vol 15 (6) ◽  
pp. 623-627 ◽  
Author(s):  
Mary B. Mitchell
Keyword(s):  
Life Cycle ◽  
Neurospora Crassa ◽  
Crossing Over ◽  
General Behavior ◽  
Phenotype Distribution ◽  
Random Distributions ◽  
Detailed Interpretation ◽  
Chromosome Segments ◽  
Map Distance

Determinations of the same map distance in different crosses often give divergent results, whereas values for unrelated map regions are often strikingly similar. This situation has been examined in samples of serially isolated spore octets, mainly from two-marker crosses. Observed ratios of phenotype distribution classes suggest more systematic modifications of random distributions than would be expected from reassociations, through crossing-over, of chromosome segments chosen unsystematically. Detailed interpretation appears impracticable, since complexities in the general behavior of the organism indicate that the ratios observed may reflect opportunities, occurring at different stages of the life cycle, for successive reassociations of genetic units.

scholarly journals Gene Conversion Alone Accounts for More Than 90% of Recombination Events at the am Locus of Neurospora crassa

Genetics ◽  
1996 ◽  
Vol 143 (1) ◽  
pp. 129-136 ◽  
Author(s):  
Frederick J Bowring ◽  
David E A Catcheside
Keyword(s):  
Molecular Markers ◽  
Neurospora Crassa ◽  
Gene Conversion ◽  
Holliday Junctions ◽  
Crossing Over ◽  
Gene Markers ◽  
General Significance ◽  
Flanking Sequences ◽  
Simple Conversion

Abstract We have used closely flanking molecular markers located ~4 kb distal and 6 kb proximal of the am locus to investigate the incidence of crossover events associated with the generation of prototrophic recombinants in a cross heteroallelic am1 am6. Ninety-three percent of prototrophs were generated by events that did not recombine the molecular markers, indicating that simple conversion accounts for the formation of most prototrophs and that associated crossovers are much less frequent (~0.07) than estimated previously using more distant flanking markers. This suggests that conversion and crossing over during meiosis may arise from distinct mechanisms or that if, as is widely supposed, conversion and crossing over result from alternate modes of resolution of Holliday junctions then, at least for the am locus of Neurospora, the mode of resolution is strongly biased in favor of retaining the parental association of flanking sequences. Because estimates of the association of conversion and crossing over based on more distant gene markers are similar for yeast and Neurospora (~0.35), our observation may have general significance.

scholarly journals Evidence for Negative Interference: Clustering of Crossovers Close to the am Locus in Neurospora crassa Among am Recombinants

Genetics ◽  
1999 ◽  
Vol 152 (3) ◽  
pp. 965-969
Author(s):  
Frederick J Bowring ◽  
David E A Catcheside
Keyword(s):  
Neurospora Crassa ◽  
Molecular Evidence ◽  
Crossing Over ◽  
Negative Interference

Abstract In response to a conflict between two mapping studies in the predicted orientation of the allele map with respect to the centromere, Fincham proposed that recombination events at the Neurospora am locus rarely have an associated crossover. Fincham considered that the elevated levels of crossing over between flanking markers in am recombinants resulted from negative interference, an increased probability of a nearby second event, and on this basis predicted a clustering of crossing over near am in these recombinants. In this article we reevaluate the data from three mapping studies of the am locus and report molecular evidence that shows crossovers to be clustered immediately proximal to am in am recombinants.

Can abortive early homologous associations promote increased crossing-over in an adjacent rearranged segment?

Genome ◽  
1988 ◽  
Vol 30 (4) ◽  
pp. 469-472 ◽  
Author(s):  
Marjorie P. Maguire
Keyword(s):  
Crossing Over ◽  
Meiotic Pairing ◽  
Pairing Behavior ◽  
Chromosome Segments

Meiotic pairing behavior of rearranged chromosome segments is compared across an informative series of combinations. The question is raised whether the simplest explanation for some peculiar findings may include a sequence of synaptic precursor events at leptotene or zygotene, the course of which may eventually strongly affect crossover frequency.Key words: meiosis, synapsis, crossing-over, rearrangement.

Characterization of Ctr family genes and the elucidation of their role in the life cycle of Neurospora crassa

2010 ◽  
Vol 47 (3) ◽  
pp. 237-245 ◽  
Author(s):  
Premsagar Korripally ◽  
Anand Tiwari ◽  
Adhikarla Haritha ◽  
Patnala Kiranmayi ◽  
Manjula Bhanoori
Keyword(s):  
Life Cycle ◽  
Neurospora Crassa

scholarly journals CROSSING OVER AND NUCLEAR PASSING IN NEUROSPORA CRASSA

Genetics ◽  
1956 ◽  
Vol 41 (4) ◽  
pp. 610-622
Author(s):  
H Branch Howe
Keyword(s):  
Neurospora Crassa ◽  
Crossing Over

scholarly journals RECONSTITUTION OF THE Rr COMPOUND ALLELE IN MAIZE

Genetics ◽  
1974 ◽  
Vol 78 (2) ◽  
pp. 691-701
Author(s):  
H K Dooner ◽  
J L Kermicle
Keyword(s):  
Homologous Chromosome ◽  
Tandem Duplication ◽  
Crossing Over ◽  
Anthocyanin Pigmentation ◽  
Genetic Length ◽  
Chromosome Segments

ABSTRACT The Rr:standard allele in maize, which conditions anthocyanin pigmentation in plant and seed tissues in the presence of appropriate complementary factors, is associated with a tandem duplication. The proximal member of the duplication carries P, the plant pigmenting determiner and the distal member member carries S, the seed pigmenting determiner. Derivatives from Rr that have lost S function are designated rr. They represent either losses of the distal member of the duplication (P derivatives) or mutations of S to s (P s). Derivatives that have lost P function are designated Rg, and represent either losses of the proximal member of the duplication (S derivatives) or mutations of P to p (p S).—All four possible types of rr/Rg heterozygotes were tested for their capacity to yield Rr reconstitution by crossing over. No Rr derivatives were obtained from P/S heterozygotes, a result consistent with the view that P and S occupy corresponding positions in homologous chromosome segments. Rr reconstitution was detected in both tandem duplication heterozygotes P s/S and P/p S, and was found to be about ten times more frequent in the latter. The ratio of Rr reconstitution in the two heterozygotes is a function of position of the anthocyanin marker within the duplicated segment. The data from these heterozygotes allow one to measure the distance between P and S, that is to say, the genetic length of the duplicated segment. This distance was found to be 0.16 map units. The highest frequency of Rr reconstitution was obtained from P s/p S heterozygotes, since direct pairing (see PDF) as well as the p//s type of displaced pairing have the potential to produce Rr derivatives. One of the Rg derivatives used in this study, Rg  6, was found to back-mutate in some sublines to Rr. The basis for this instability remains unknown.

Elimination of Active Tad Elements during the Sexual Phase of the Neurospora crassa Life Cycle

2001 ◽  
Vol 33 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Cindy Anderson ◽  
Qinling Tang ◽  
John A Kinsey
Keyword(s):  
Life Cycle ◽  
Neurospora Crassa
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