Since the discovery in 1989 that mutations in cystic fibrosis transmembrane conductance regulator (CFTR) underlie cystic fibrosis (CF), the most common life shortening genetic disorder in Caucasians, it has been possible to identify heterozygous mutation carriers at risk of having affected children. The Human Genetics Society of Australasia has produced a position statement with recommendations in relation to population-based screening for CF. These include: (1) that screening should be offered to all relatives of people with or carriers of CF (cascade testing) as well as to all couples planning to have children or who are pregnant; (2) the minimum CFTR mutation panel to be tested consists of 17 mutations which are those mutations that are associated with typical CF and occur with a frequency of 0.1% or higher among individuals diagnosed with CF in Australasia; (3) that genetic counselling is offered to all couples where both members are known to have one or two CFTR mutations and that such couples are given the opportunity to meet with a physician with expertise in the management of CF as well as a family/individual affected by the condition.

We have examined the retinal decussation patterns in pigmented ferrets that were either wild-type sable or heterozygous with one albino gene. Unilateral injections of horseradish peroxidase were made into the optic tract and labeled ganglion cells visualized in retinal wholemounts. In both wild-type and heterozygous ferrets, those ganglion cells in the temporal retina with the largest cell bodies projected only to the contralateral side of the brain. The total number of ipsilaterally projecting ganglion cells did not differ with the genotype of the animal. The numbers ranged from 5471–6759 cells. Unlike the cat, there is no difference in retinal decussation patterns in wild-type sable ferrets and heterozygous ferrets carrying one albino gene.

Generally women are believed to be more discriminating than men in the use of color names and this is often taken to imply superior color vision. However, if both X-chromosome linked color deficient males (∼8%) and females (<1%) as well as heterozygote female carriers (∼15%) are excluded from comparisons, then differences between men and women in red-green (RG) color discrimination have been reported as not being significant (e.g., Pickford, 1944; Hood et al., 2006). We re-examined this question by assessing the performance of 150 males and 150 females on the color assessment and diagnosis (CAD) test (Rodriguez-Carmona et al., 2005). This is a sensitive test that yields small color detection thresholds. The test employs direction-specific, moving, chromatic stimuli embedded in a background of random, dynamic, luminance contrast noise. A four-alternative, forced-choice procedure is employed to measure the subject's thresholds for detection of color signals in 16 directions in color space, while ensuring that the subject cannot make use of any residual luminance contrast signals. In addition, we measured the Rayleigh anomaloscope matches in a subgroup of 111 males and 114 females. All the age-matched males (30.8 ± 9.7) and females (26.7 ± 8.8) had normal color vision as diagnosed by a battery of conventional color vision tests. Females with known color deficient relatives were excluded from the study. Comparisons between the male and female groups revealed no significant differences in anomaloscope midpoints (p = 0.709), but a significant difference in matching ranges (p = 0.040); females on average tended to have a larger mean range (4.11) than males (3.75). Females also had significantly higher CAD thresholds than males along the RG (p = 0.0004), but not along the yellow-blue (YB) discrimination axis. The differences between males and females in RG discrimination may be related to the heterozygosity in X-linked cone photo pigment expression common among females.

It might be expected that normal trichromatic females would perform as well as normal trichromatic males of the same age when tested with standard clinical color-vision tests that use pseudoisochromatic vanishing designs on neutral gray backgrounds such as the Hardy-Rand-Rittler (HRR) pseudoisochromatic plates and the Neitz Test of Color Vision (NTCV). Here 2966 children aged 6–13 years from four municipalities in Norway were tested in their school classrooms with the NTCV. Children who made errors on the test were retested. 187 males and 152 females made one or more errors on retest, and each was tested individually on the Richmond HRR Fourth Edition. 8% of the males were defined as color deficient when a double criterion for failing was applied, that is, one or more errors on the NTCV and two or more errors on the HRR. The calculated frequency of color-deficient females (homozygotes) for the same criterion is 0.42%. By contrast, 3% of females failed the criterion that gave a stable population of color-deficient males. This result is considered in relation to reports of female carriers of color-vision deficiency having problems with the Ishihara test and of females having poorer color discrimination than males.

The oocysts of Plasmodium falciparum that form on the midgut wall of anopheline vectors represent the meiotic products of the sexual cycle of the parasite and are useful for genetic analyses. Recognizing the limitations of current markers for the analysis of genetic variation, we describe a protocol for the DNA isolation and PCR amplification of microsatellite loci from individual oocysts. We present a simple method for the storage and isolation of individual Plasmodium oocysts from wild-caught mosquitoes and demonstrate that it is possible to extract sufficient oocyst DNA for approximately 50 amplifications. Genotyping was successful for 10 microsatellite loci and, using Genescan technology, we found extensive microsatellite polymorphism in an analysis of a dozen oocysts from each of 2 Anopheles gambiae female specimens collected within 6 months at the same location in northern Tanzania. All of the loci exhibited at least 2 alleles, with a maximum of 5. Homozygous and heterozygous oocysts could easily be discerned, but most of the oocysts were homozygous. The procedure has great potential for shedding light on genetic mechanisms operating during meiosis in mosquito vectors and the influence this may have on the genetic structure of natural populations of P. falciparum.

This work studies the long-term effects of mutation and selection pressures on a diploid population embracing many genetic types. A number of results previously established for the simpler asexual case (see [4]) are extended to the cases of random mating and complete inbreeding (Theorem 1), and then, under particular conditions, to certain circumstances of mixed random mating and inbreeding (Theorem 3 and Corollary 1). Several implications for sex and diploidity are drawn from Theorem 2 and its corollaries. Further biological interpretations of these findings, especially of Theorem 2, are given in [3].