Half-chromatid mutation as a possible cause of mosaic males and females in Hymenoptera and rare fertile male tortoiseshell cats

Half-chromatid mutations occur when a single base change in a gamete is transmitted to the zygote, which, after DNA replication and cleavage, will result in a mosaic individual. These mutations will be passed on through the germ plasm and also may be expressed somatically. Half-chromatid mutation has been suggested to account for the observed lower frequency of males than expected for lethal X-linked recessive disorders in humans, such as Lesch-Nyhan syndrome, incontinentia pigmenti, and Duchene muscular dystrophy. Although attention has been paid to half-chromatid mutation in humans, it otherwise has been ignored. Here I show that half-chromatid mutation in haplodiploid organisms, such as Hymenoptera, has some interesting and important consequences: (i) since all genes follow the X-linked pattern of inheritance, half-chromatid mutations should be relatively easier to detect; (ii) recessive mutations of all viabilities may be expected; (iii) mosaics of both sexes are expected in haplodiploids with half-chromatid mutation; (iv) gynandromorphs could result from half-chromatid mutation at the sex-determination locus, in species with single-locus complementary sex-determination. Finally, half-chromatid mutation can account for the rare fertile male tortoiseshell phenotype observed in the domestic cat, Felis catus, and which still has not been fully accounted for by other mechanisms.

Asymmetry of Edema Formation: The Possibility of a Somatic Mosaic

A 57-year-old woman experienced an abnormal feeling on the left side of her neck and difficulty breathing 90 minutes after eating Chinese noodles. She had a history of removal of a left sphenoid ridge meningioma one year earlier. She had experienced rigidity of her left neck and peripheral cold sensation on her left side in winter since approximately 10 years of age. She had experienced peripheral swelling of her left side and lower back pain of unknown origin on her left side several times. She had suffered for oral allergy syndrome since she was young. She sometimes experienced a tingling sensation on her lips and an unpleasant feeling in her throat after eating some types of fruit. On arrival, 180 minutes after eating the noodles, she had clear consciousness and stable vital signs. She had left neck and chest swelling without color change. Her difficulty breathing subsided spontaneously. A blood analysis revealed an increased level of immunoglobulin E. Neck computed tomography (CT) with contrast medium and magnetic resonance imaging (MRI) revealed left-side-limited edema in the subcutaneous area and surrounding esophagus and bronchus. These radiological findings denied hemorrhaging or pseudoaneurysmal formation. She underwent observational admission. After her edema improved, she was discharged on the third hospital day. A follow-up examination one week later showed the complete resolution of the neck and chest edema. A blood allergen test did not reveal the cause of the edema. The mechanism underlying the asymmetric transient edema after eating in the present case may involve somatic mosaic.

Control of mating plug expelling and sperm storage in Drosophila: A gynandromorph- and mutation-based dissection

INTRODUCTION

In this study, we analyzed gynandromorphs with female terminalia, to dissect mating-related female behaviors in Drosophila.

MATERIALS AND METHODS

We used gynandromorphs, experimentally modified wild-type (Oregon-R) females, and mutant females that lacked different components of the female reproductive apparatus.

RESULTS

Many of the gynandromorphs mated but did not expel the mating plug (MP). Some of these - with thousands of sperm in the uterus - failed to take up sperm into the storage organs. There were gynandromorphs that stored plenty of sperm but failed to release them to fertilize eggs. Expelling the MP, sperm uptake into the storage organs, and the release of stored sperm along egg production are separate steps occurring during Drosophila female fertility. Cuticle landmarks of the gynandromorphs revealed that while the nerve foci that control MP expelling and also those that control sperm uptake reside in the abdominal, the sperm release foci derive from the thoracic region of the blastoderm.

DISCUSSION AND CONCLUSION

The gynandromorph study is confirmed by analyses of (a) mutations that cause female sterility: Fs(3)Avar (preventing egg deposition), Tm2^gs (removing germline cells), and iab-4^DB (eliminating gonad formation) and (b) by experimentally manipulated wild-type females: decapitated or cut through ventral nerve cord.

The effects of increased temperature on electroretinograms of temperature-sensitive paralysis mutants of Drosophila melanogaster

Mutations within the shibire locus of Drosophila melanogaster are non-complementing alleles which result in reversible paralysis at 29 degrees but retention of normal locomotor behavior at 22 degrees . Electroretinograms of six of the mutants have been recorded at various temperatures. Two changes occurred in the electroretinograms of flies carrying most of the alleles at high temperature: they lost the "on"- and "off"- transients of the normal electroretinogram, and the fast decay of the receptor potential was attenuated. For flies with four of the alleles, a base-line oscillation was also observed. Analysis of electroretinograms of mosaic shibire flies indicates that the loss of the transients can be attributed to both a pre-synaptic and a post-synaptic effect.