In mammals, the meiosis division in testes produces equal numbers of two different types of gametes: X chromosome-bearing sperm (X-spermatozoa) and Y chromosomebearing sperm (Y-spermatozoa), which have equal potential to fertilize the oocytes. Therefore, the expected 1: 1 sex ratio is observed. However, under some conditions like endocrine disruptors (EDs) exposure the sex ratio is deviated than the expected with more males or more females. And recently many hypotheses have been postulated to explain the mechanism of sex ratio deviation; however none of them introduced a proven experimental explanation. To solve this enigma, we hypothesized that the differences between X- and Y-spermatozoa survivability under specific conditions due to differences in their chromosome contents are the key leading to the sex ratio alteration. To examine our hypothesis, we combined two techniques; first, hypo-osmotic swelling (HOS) test that was applied to test viability of spermatozoa and second, fluorescence in situ hybridization that was applied on HOS-treated spermatozoa to define sex chromosome composition. In the present study, human spermatozoa were incubated with a group of EDs represent a widespread chemicals in the environment bisphenol A (BPA, 100 μM), nonylphenol (NP, 10 μg/ml), 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD, 2.5 μg/ml), genistein (Gen, 100 μM), and the following pesticides, dibromochloropropane (DBCP, 10 μg/ml), atrazine (Atraz, 500 μM), and diazinone (Diaz, 500 μM) for 6 hr at 37℃ in 5% CO2. Then, the viability of spermatozoa and their sex chromosome contents were evaluated simultaneously. Among seven chemicals studied only four chemicals (Atraz, DBCP, TCDD, and Diaz) significantly decreased Y-sperm viability when compared to those of X-spermatozoa in the same treatment group and viability of Y-spermatozoa when compared to those in the negative and positive (DMSO) control groups (p<0.05). Also, in these four treatment groups the sex ratio of live sperm population was significantly lowered compared to the control groups (p<0.05). Otherwise, Gen, BPA, and NP did not show any significant effect on viability of Yspermatozoa or decreasing sex ratio in live sperm population as compared to the control groups. It has been proven that TCDD, DBCP, and the pesticides decrease the sex ratio, but the same effect was not observed in case of Gen, BPA, and NP. From the present findings, there is no doubt that the EDs may alter sex ratio via decreasing Y-spermatozoa viability.

The paternal sex ratio (PSR) chromosome is considered as an extremely selfish genetic element. It has only been found in the two hymenopteran insects- Nasonia and Trichogramma- with haplodiploid sex determination. When an egg is fertilized by sperm bearing PSR, the paternal genome is destroyed by PSR soon after fertilization resulting in haploid restoration and the egg develops into a male with only the maternal genome and PSR itself. Recently PSR is paid much attention, since it may be used for controlling haplodiploid pests. PSR can be successfully transferred from its natural host, T. kaykai to the novel host, T. deion. In the two hosts another sex ratio distorter, Wolbachia, is found. Wolbachia is a cytoplasmically inherited bacterium that induces parthenogenesis in this genus resulting in female offspring production without fertilization. The transmission efficiency of PSR in T. deion is lower than that in T. kaykai and is negatively influenced by the Wolbachia infection. The results show that 1) there is a negative host genetic background effect on the transmission of PSR in the novel host, 2) the transmission efficiency becomes even lower, when PSR males are infected with Wolbachia. The results imply that complex interactions among the bacterium, PSR and the species specific genetic background.

Drosophila simulans와 D. mauritiana는 동일 subgroup에 속하는 동포종으로, 전자는 전세계 분포종이며, 후자는 Mauritius 섬에만 서식하는 지역종이다. D. simulans의 성즐(sex comb)은 약 9.83개의 치열로 구성되어 있으며, D, mauritiana의 성즐 치열수는 약 12.90개 정도이다. D. simulans의 생식궁(genital arch)은 큰 반월형이며, D. mauritiana는 가는 막대형이다. 두 종간 성즐의 치열수와 생식궁의 형태적 차이에 미치는 X 염색체의 효과를 알아보기 위한 유전적 분석을 실시하였으며, 이를 위하여 X 염색체상 돌연변이 유전자들을 가지는 D. simulans 계통과 정상의 D. mauritiana 사이의 잡종 TEXF1/TEX을 부모계통과 역교배를 실시하여 얻은 자손들을 대상으로 상기 두가지 형질의 분석을 실시하였다. F1의 성즐 치열수는 평균 11.79개 정도였으며, 외부생식기의 일반적인 형태는 D. simulans와 D. mauritiana의 중간형이었다. 성즐의 치열수와 외부생식기의 주요 특징분석에서 X 염색체 효과에 따른 유의적인 차이는 거의 없는 것으로 나타났다.