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General Information
D. melanogaster
FlyBase ID
Feature type
Associated gene
Associated Insertion(s)
Carried in Construct
Also Known As
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:

W922term | Blm-PA

Reported amino acid change:



G to A nucleotide change at the second or third position of the wild type Trp codon leads to a nonsense mutation (exact site of mutation unspecified). The mutation was annotated at the second base of the codon.

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

FlyBase curator comment: This is a TGG to TAG mutation.

Nucleotide substitution: G?A.

Amino acid replacement: W922term.

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 ( 1 )
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

BlmN1/BlmD2 animals are hyper-sensitive to the cross-linking agent HN2, the mono-adduct generator MMS, and ionizing radiation.

Spontaneous mitotic crossovers are elevated in BlmN1/BlmD2 males.

BlmN1/BlmD2 animals show a severely decreased ability to complete 'synthesis-dependent strand annealing' repair of a DNA gap.

No significant change in single-strand annealing frequency between mus309D2/mus309D3 mutant flies and controls when the sequence in question has 100% sequence identity (MtnB2x259gen.Scer\SceI.RS.T:Avic\GFP-EGFP). A small increase in single stranded annealing is observed during the repair of a construct with a 1-bp mismatch in mutant flies (MtnBmutgen.Scer\SceI.RS.T:Avic\GFP-EGFP). With a more divergent construct (MtnBcDNA-gen.Scer\SceI.RS.T:Avic\GFP-EGFP a strong increase in single stranded annealing frequency is detected in mus309D2/mus309D3 mutants.

Suppression of homologous single stranded annealing (SSA) is relaxed in mus309D2/mus309D3 mutants, resulting in a 4.5-fold elevation in SSA frequencies. Discontinuous repair patterns are never seen in these mutants.

Embryos derived from mus309D2/mus309D3 and mus309N1/mus309D2 females have an extremely low hatch rate.

Only 40% of the embryos derived from mus309N1/mus309D2 females have cellularised by 4-6 hours after egg laying, and none have gastrulated by this time (in contrast to embryos derived from wild-type females where 99% have cellularised and 96% have gastrulated by this time).

mus309N2/mus309D2 females show an increased rate of X chromosome meiotic nondisjunction compared to wild-type females.

mus309D2/mus309D3 larvae are hypersensitive to gamma radiation, showing reduced survival to adulthood after irradiation with doses of radiation that do not have a large effect on the survival of wild-type larvae.

Studies of excision and repair events of P{hswa} in mus309N1/mus309D2, mus309N2/mus309D2 and mus309D2/mus309D3 males indicate that synthesis-dependent strand annealing (SDSA) is severely compromised in these animals.

mus309N1/mus309D2, mus309N2/mus309D2 and mus309D2/mus309D3 males show elevated rates of mitotic crossing over compared to control males.

mus309D2/mus309D3 mutants have a similar frequency of single-strand annealing repair (SSA) compared to controls in a P{wIw.FRT} hemizygous assay to study DNA double-stranded break repair when assayed at 32oC or 38oC.

Homozygotes of mus309D2 are viable.

Compared with wild-type flies, mus309D2/Df(3R)T-7 flies display altered measurements of parameters related to double-strand break repair.

BlmD2/BlmD3 flies are semilethal.

The complete copia element in wa.hs has an LTR at each end. Following excision of P{hswa}, repair by SDSA (synthesis-dependent strand annealing) can lead to excision of this copia element due to annealing at these LTRs, resulting in red eyed progeny. Incomplete SDSA, where joining has occurred independently of annealing of homologous ends, can delete parts of the w ORF in wa.hs resulting in yellow eyed progeny. The frequency of red eyed progeny following excision of P{hswa}sdwa using H{PΔ2-3}HoP2.1 (and therefore of complete SDSA) is decreased from 6% to 0.2% in a mus309D2/mus309D3 background, but the frequency of yellow eyed progeny (and therefore of incomplete SDSA) is increased from 10% to 15.5%. This background also increases the proportion of hemizygous lethal sd deletions resulting from this excision event (from 2.4% to 25%), and the proportion of non-lethal sd deletions from 7% to 35.5%.

mus309D2/Df(3R)T-7 animals are sensitive to methyl methanesulfonate. Chromosome nondisjunction and chromosome loss is increased more than tenfold in mus309D2/Df(3R)T-7 males relative to wild type and heterozygous controls. An elevated frequency of sperm which have lost one of two dominant markers on opposite ends of the Y chromosome is also seen.

mus309D2/mus309D3 animals show no defects in a DNA damage checkpoint assay.

mus309D2/mus309D3 mutants are threefold more sensitive to X rays than wild-type flies.

Unable to repair double-strand DNA breaks. Hypersensitive to methyl methanesulfonate (MMS).

Hypersensitive to methyl methanesulfonate. Sensitive to 0.008% HN2.

External Data
Show genetic interaction network for Enhancers & Suppressors
Phenotypic Class
Enhanced by
Suppressed by
NOT suppressed by

BlmD3/BlmD2 has female sterile phenotype, non-suppressible by Irbp6.8

BlmD3/BlmD2 has chemical sensitive phenotype, non-suppressible by Irbp6.8

BlmD3/BlmD2 has female sterile phenotype, non-suppressible by IrbpΔ

BlmD3/BlmD2 has chemical sensitive phenotype, non-suppressible by IrbpΔ

Enhancer of
Suppressor of

mus309[+]/BlmD2 is a suppressor of visible phenotype of Caf1-180UAS.cSa, Scer\GAL4ey.PH

mus309[+]/BlmD2 is a suppressor of increased cell death phenotype of Caf1-180UAS.cSa, Scer\GAL4ey.PH

BlmD2 is a suppressor of viable phenotype of mus815.1

Phenotype Manifest In
Suppressed by
NOT suppressed by
Suppressor of

mus309[+]/BlmD2 is a suppressor of eye phenotype of Caf1-180UAS.cSa, Scer\GAL4ey.PH

Additional Comments
Genetic Interactions

A very small proportion of Pol32L30/Pol32L27 adults show an etched abdomen phenotype; this phenotype is not much affected in a BlmD2/+ background.

The rate of spontaneous mitotic crossovers in BlmN1/BlmD2 Fancm0693/Df(3R)ED6058 males is not significantly different from that in Fancm0693/Df(3R)ED6058 males, but is significantly lower than in BlmN1/BlmD2 males.

mus309N1/mus309D2 slx1F93I and mus309N1/mus309D2 Df(3R)HKK1, Dp(3;3)HKK2 double mutant animals die as early pupae, larvae lack imaginal discs and larval neuroblasts are frequently polyploid.

mus309N1/mus309D2 mus312D1/mus312Z1973 double mutant larvae have small brains, lack imaginal discs and have a reduced number of salivary gland imaginal ring cells. The nuclei of the remaining salivary gland imaginal ring cells appear larger than normal. Mitotic neuroblasts in these larvae show extreme genome instability; no mitotic nuclei with completely intact chromosomes are detected and approximately one-third show polyploidy.

Mitotic neuroblasts in mus81Nhe ; mus309N1/mus309D2 double mutant larvae show an increased frequency of broken chromosomes compared to wild type.

The addition of spn-Aunspecified significantly decreases the number of chromosome breaks seen in mitotic neuroblasts of mus81Nhe ; mus309N1/mus309D2 larvae.

Genunspecified/Df(3L)Exel6103 mus309N1/mus309D2 spn-Aunspecified triple mutant larvae have small brain and generally lack imaginal discs (although very small rudimentary discs are occasionally visible). Salivary gland imaginal ring cells are reduced in number and have enlarged nuclei. Mitotic neuroblasts have numerous chromosome breaks.

The addition of spn-Aunspecified suppresses the the chromosome breakage and polyploidy phenotypes seen in mitotic neuroblasts of mus309N1/mus309D2 mus312D1/mus312Z1973 larvae, and also suppresses the defects in the salivary gland imaginal ring cells seen in the mus309N1/mus309D2 mus312D1/mus312Z1973 double mutants. However, addition of spn-Aunspecified does not suppress the pupal lethality, small brains and lack of imaginal discs seen in the mus309N1/mus309D2 mus312D1/mus312Z1973 double mutants.

Mitotic neuroblasts in Genunspecified/Df(3L)Exel6103 mus309D2/mus309N2 double mutant larvae show an increased frequency of broken chromosomes compared to wild type.

mus309D2/mus309N2 mus312D1/mus312Z1973 double mutant larvae generally lack imaginal discs (although small, severely underdeveloped discs are sometimes seen in third instar larvae).

mus312D1/mus312Z1973, mus309D2/mus309N1 double mutants are inviable, dying after pupariation. Third-instar larvae have melanotic tumors and lack larval imaginal discs. Larval brains of double mutants are greatly reduced in size.

The spn-A3/spn-A093A transheterozygous condition does not suppress the lethality of mus312D1/mus312Z1973, mus309D2/mus309N1 double mutants.

The small-eye phenotype of flies expressing Caf1-180Scer\UAS.cSa under the control of Scer\GAL4ey.PH is suppressed by heterozygous BlmD2.

The double mutant of mus815.1 and mus309D2 is lethal, even though both mutations are viable individually. Most of the double mutants survive until the late larval stages, but die during pupation.

The triple mutant of mus815.1, mus309D2 and spn-A1 is lethal.

The elevated recombination caused by mus309D2 is abolished by spn-A1.

spn-A3/spn-A093A suppresses the increase deletions resulting from the H{PΔ2-3}HoP2.1 driven of excision of P{hswa}sdwa due to a mus309D2/mus309D3 background.

okr17-11/okrA19-10 mus309D2/mus309D3 double mutants show a synergistic effect on sensitivity to X rays; the sensitivity is increased 40 fold compared to wild-type in double mutants. mus309D2/mus309D3 mutants are slightly sensitive to methyl methanesulfonate (MMS). okr17-11/okrA19-10 mus309D2/mus309D3 double mutants do not show a synergistic effect on sensitivity to MMS.

Xenogenetic Interactions
Complementation and Rescue Data
Partially rescued by

Df(3R)T-7/BlmD2 is partially rescued by Blmhs.PK

Images (0)
Stocks (3)
Notes on Origin


External Crossreferences and Linkouts ( 0 )
Synonyms and Secondary IDs (5)
References (24)