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General Information
D. melanogaster
FlyBase ID
Feature type
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
mei-9a, A
Key Links
Allele class
Nature of the Allele
Allele class
Mutations Mapped to the Genome
Additional Notes
Nucleotide change:


Reported nucleotide change:


Amino acid change:

D701N | mei-9-PA; D701N | mei-9-PB

Reported amino acid change:



Position of mutation on reference sequence inferred by FlyBase curator. Authors protein sequence lacks 43 N-terminal amino acid residues.

Associated Sequence Data
DNA sequence
Protein sequence
Progenitor genotype
Nature of the lesion

Amino acid replacement: D658N. Nucleotide substitution: G2289A.

Expression Data
Reporter Expression
Additional Information
Marker for
Reflects expression of
Reporter construct used in assay
Human Disease Associations
Disease Ontology (DO) Annotations
Models Based on Experimental Evidence ( 0 )
Modifiers Based on Experimental Evidence ( 0 )
Comments on Models/Modifiers Based on Experimental Evidence ( 0 )
Disease-implicated variant(s)
Phenotypic Data
Phenotypic Class
Phenotype Manifest In
Detailed Description

Two pro-oocytes are visible in 69.6% of region 3 cysts in homozygous females (as assayed by c(3)G staining) compared to a frequency of 9.5% in wild type.

The progeny of mutant females show a 90% decrease in meiotic crossover products and a 60% increase in noncrossover products (NCOs) compared to wild type. The frequency of postmeiotic segregation in NCOs of mutant females (16%) is significantly higher than that in NCOs from wild type (where postmeiotic segregation is exceedingly rare).

Mutant females show reduction in the overall frequency of crossing over on the second chromosome compared to wild type. The reduction in crossing over is the same in the centromere-proximal interval as in other regions of the chromosome.

mei-9a/mei-9a mutant female meioses exhibit a lower frequency of recombination, and an increase in post-meiotic segregation, as compared to wild type.

mei-9a/mei-9A2 females show 30% X chromosome nondisjunction, compared to 0.33% in wild-type females. mei-9a/mei-9A2 larvae are hypersensitive to ultraviolet light and nitrogen mustard.

Mutants show an increased frequency of egg chamber degeneration after irradiation, and also "rescue" of some oocytes from induction of dominant lethal mutations after irradiation.

The formation of mobile nucleoli is enhanced in these excision repair mutants.

Excision repair capacity is deficient and post-replication repair capacity is normal.

Mutations exhibit an absolute deficiency in the capacity to excise UV-induced pyrimidine dimers (FBrf0028769).

The median and maximal lifespans of mei-9a flies are significantly lower than that of wild-type flies.

Flies are hypersensitive to killing by γ-rays.

Sensitive to methyl methanesulfonate.

Homozygotes have an increased frequency of X chromosome non-disjunction.

Excision repair deficient.

The presence or absence of mei-9a has little effect on the reversion rate of RpII2159.

Approximately 20% of embryos hatch.

Reduces exchange uniformly throughout the euchromatin. Deleted chromatids are occasionally recovered.

Meiotic crossing-over is reduced by a factor of 1/12 in homozygous or mei-9a/mei-9b females. The frequency of gene conversion at the ry locus is unaffected in homozygous or mei-9a/mei-9b females. Post-meiotic segregation events, manifested as mosaic progeny, are produced at high frequency in homozygous and mei-9a/mei-9b females.

Homozygotes and hemizygotes show a higher frequency of spontaneous chromosome aberrations in neuroblast metaphases than wild-type larvae. The ratio of chromatid breaks to isochromatid breaks is 4.8-6.2. Approximately half of the breaks are heterochromatic and half are euchromatic. The breaks appear to be randomly distributed among the chromosomes. Breaks are 1.4-1.6 times more frequent in females than in males.

mutagen sensitive reduces exchange mitotic instability

External Data
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Phenotype Manifest In
Suppressed by

mei-9a has phenotype, suppressible by rad2011

NOT Suppressor of

mei-9a is a non-suppressor of phenotype of mei-41D18


mei-41D18, mei-9a has oocyte nucleus & meiotic cell cycle phenotype

mei-41[+]/mei-41D18, mei-9a has oocyte nucleus & meiotic cell cycle phenotype

grpunspecified, mei-9a has oocyte nucleus & meiotic cell cycle phenotype

Additional Comments
Genetic Interactions

The rate of spontaneous mitotic crossovers in Fancm0693/Df(3R)ED6058 males is not affected if animals are also mutant for mei-9a, or if these animals are also mutant for both slx1F93I and mei-9a.

mei-9a ; yemα1/Df(3R)3450 oocytes undergo precocious anaphase I (as occurs in mei-9a single mutants), but meiosis II spindles are rarely observed in the double mutants (in contrast to mei-9a single mutants where a greater proportion of the oocytes reach meiosis II).

The high frequency of region 3 cysts containing two pro-oocytes that is seen in mei-9a homozygous females is suppressed by mei-2181.

mei-9a/mei-9a mei-2181/mei-2181 double mutant female meioses exhibit a lower frequency of recombination, as compared to wild type, and a lower frequency of post-meiotic segregation, as compared to mei-9a/mei-9a single mutants.

About a quarter of nuclei in mei-9a/mei-9a; mei-41D18/+ oocytes exhibit premature anaphase (or later) meioses. When mei-9a is added to either grpunspecified or grpunspecified/+ flies, precocious anaphases are sometimes seen.

Xenogenetic Interactions
Complementation and Rescue Data
Images (0)
Stocks (15)
Notes on Origin

An endonuclease activity which is specific for partially depurinated DNA is reduced in mei-9a cell lines and in extracts of mei-9a larval brain ganglia compared to wild-type.

The activity of an apurinic (AP) endonuclease is reduced by 98% in mei-9a mutants compared to wild-type. Mixing experiments between extracts of mei-9a and wild-type embryos suggests that the mei-9 locus probably does not encode the AP endonuclease itself.

Simple meiotic gene conversion tracts produced in mei-9 mutants have been compared with those produced in wild-type.

mei-9a has no detectable effect on the recovery of chromosomes undergoing P-element transposition.

External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (8)
References (58)