Zero-inflated models assume there are two processes generating the zeros in the data and models these two processes separately, a poisson GLM for the count data and a binomial GLM for the occurrence of zeros. At 10 dpf, ml of fish water was added to each tank to facilitate counting of larvae.
Moreover, we were able to obtain several strongly male-biased zebrafish families by selective crossing of brooders that produced higher proportion of male offspring over a few generations. In a well-differentiated sex chromosomal system, the SD region should be unique to the heterogametic sex chromosome.
This will result in duplication of the remaining haploid genome, hence the name double haploids. Table 3 Results from generalized linear models examining egg number, offspring number and hatching success in BC2 crosses. Among the reasons that make zebrafish a popular laboratory model is its short generation time.
Conclusions For this study, we performed classical breeding experiments together with large-scale genomic analyses to show that zebrafish sex is determined genetically with no sign of a chromosomal sex determination system. Aneuploidy is the condition of having less than monosomy or more than polysomy the normal diploid number of chromosomes.
Congenital adrenal hyperplasia CAH is an inherited autosomal recessive condition that can affect both boys and girls. However, none of the environmental factors exerted a strong effect on sex within their natural range, and some of them seemed to be largely dependent on the fish genotype. Reasons for this exception to Haldane's rule are not clear.
Based on our data and the recent aforementioned association study we propose that the number of genes contributing to the sex determination process might be far more than just a handful. Checkered bars indicate males, and solid bars indicate females.
Chromosome Res 4: 29— Results Wide-ranging sex ratios among zebrafish families The classical method to determine if a species is using chromosomal sex determination system is to analyze the sex ratio among many families . The data reviewed so far on sex chromosome searches in zebrafish shows the following: i there is no cytogenetic evidence of heteromorphic chromosomal pair; ii the observed progeny sex ratios from various genome manipulation studies did not concur with those expected from a simple sex chromosome model; iii lack of substantial, universal differences between genomes of the two sexes in multiple strains and iv genome-wide linkage analysis identified multiple regions on different chromosomes associated with SD.
The faster X theory favours the occurrence of Haldane's rule in both male and female heterogametic species but has the weakest empirical support out of the three main theories. Molecular mechanisms of sex determination and gonadal sex differentiation in fish.
Double haploid. These loci are typically dispersed throughout the genome, but in some teleost species a few of them might be located on a preferential pair of sex chromosomes. A strong determinant should produce broods of very similar sex ratio. In the second-generation BC1 , reciprocal F1 hybrid females and males were backcrossed to both parental species to test whether the species obey Haldane's rule for sterility and if X-linked incompatibilities contribute to offspring inviability.
Transcriptomic analyses reveal novel genes with sexually dimorphic expression in the zebrafish gonad and brain. Genetic variation for postzygotic reproductive isolation between caenorhabditis briggsae and caenorhabditis sp.