Structural chromosome aberrations or chromosome mutations represent apart from aneuploidies the most frequent pathologic findings in applied chromosome diagnostics. But they also occur as combinations of both types as in unstable rearrangements or in chaotic karyotypes of early stages of embryonic development. Depending on the indication for chromosome analysis—child with developmental retardat...

Increased prenatal exposure to testosterone (T) in females of an opposite-sex (OS) twin pair may have an effect on the development of sex-typical cognitive and behavioral patterns. The prenatal exposure to T due to hormone transfer in OS twin females may occur in two ways, one directly via the feto-fetal transfer route within the uterus, the other indirectly through maternal-fetal transfer and ...

An assemblage of non-Mendelian sex ratio elements occurs in natural populations of the parasitoid wasp Nasonia vitripennis. These include Maternal Sex Ratio (MSR), a cytoplasmic element that causes nearly all-female families, and Paternal Sex Ratio (PSR), a B chromosome that causes all-male families. The PSR chromosome is transmitted via sperm but causes destruction of the paternal chromosomes ...

The sex-determining systems of arthropods are surprisingly diverse. Some species have male or female heterogametic sex chromosomes while other species do not have sex chromosomes. Most species are diploids but some species, including wasps, ants, thrips and mites, are haplodiploids (n in males; 2n in females). Many of the sexual aberrations, such as sexual mosaics, sex-specific lethality and co...

There is growing evidence that sex determination in a wide range of organisms is determined by interactions between maternal-effect genes and zygotically expressing genes. Maternal-effect genes typically produce products (e.g., mRNA or proteins) that are placed into the egg during oogenesis and therefore depend upon maternal genotype. Here it is shown that maternal-effect and zygotic genes are ...

The relationship between some biological parameters (mortality, longevity, fertility, fecundity and sex ratio) and segregation of second chromosomes in heterozygous and homozygous SD males has been analyzed. The results obtained in SD/SD+ heterozygous males show: (1) their reduced fertility with respect to that of control males, (2) an alteration in the sex ratio in the SD+ progeny only, and (3...

Ray and colleagues present data on variation in birth sex ratios among Ontario newborns, showing a significant male-biased sex ratio at birth among multiparous Indian and South Korean mothers. The authors suggest that women from these countries may be using prenatal sex determination and selective termination. However, there are plausible, adaptive reasons for variations in both individualand p...

Disorders of sex development (DSD) with or without ambiguous genitalia require medical attention to reach a definite diagnosis. Advances in identification of molecular causes of abnormal sex, heightened awareness of ethical issues and this necessitated a re-evaluation of nomenclature. The term DSD was proposed for congenital conditions in which chromosomal, gonadal or anatomical sex is atypical...

1. The purpose of the in vitro chromosome aberration test is to identify agents that cause structural chromosome aberrations in cultured mammalian cells (1)(2)(3). Structural aberrations may be of two types, chromosome or chromatid. With the majority of chemical mutagens, induced aberrations are of the chromatid type, but chromosome-type aberrations also occur. An increase in polyploidy may ind...