Sterility phenotype

Klinefelter syndrome (47,XXY) is seen in approximately 1 in 1,000 males (all individuals with this condition have a male phenotype because they have a Y chromosome). Klinefelter males are nearly always sterile because of atrophy of the seminiferous tubules. They tend to be taller than average, with abnormally long arms and legs. Breast development (gynecomastia) is seen in about one third of cases, and the IQ is on average 10-15 points below that of unaffected siblings. Individuals have also been seen with 48.XXXY and 49,XXXXY karyotypes the additional X chromosomes produce a more severely affected phenotype. 

Recent studies from our laboratory additionally indicate that the transition from the monocyte to mature PAM T-suppressive phenotype is time dependent and cytokine sensitive. Following recruitment into the lung via a sterile inflammatory stimulus, murine monocytes require 5 days for full maturation (Bilyk and Holt, 1994). In addition, the presence of cytokines such as GM-CSF (especially if free TNFa is also available) inhibits the expression of suppressive activity (Fig. 1.5). If mature PAMs are cultured continuously in the presence of GM-CSF, their T cell-interactive phenotype reverts to that of... 

The answer is b. (Murray, pp 812-828. Scriver, pp 3-45. Sack, pp 57—84. Wilson, pp 123-148.) The recurrence risk for aneuploidies caused by meiotic nondisjunction is about 1% in addition to the maternal age-related risk. It is not known why the risk for aneuploidy increases slightly after an affected child is born, but parental karyotypes are almost always normal. Surveys of penal institutions have revealed an increased incidence of 47,XYY individuals, but other conditions with mental disability are increased as well. As with other chromosomal syndromes, the phenotype of 47,XYY is variable and can be found coincidentally in normal males. It would therefore be inappropriate to label a child as abnormal in school unless there have been previous concerns about a medical disorder. Males with Klinefelter s syndrome (47,XXY), rather than those with 47,XYY syndrome, are often sterile and may require supplementation with male hormones. 

Metal ions and complexes may induce chromosome aberrations and Cu + and Pb + (Levan, 1945) or phenyl and methyl mercury (Ramel, 1969) very efficiently lead to disturbances of the nuclear spindle which are of a kind that could lead to aneuploidy. Diploids are less suited to detect the phenotypic effect in Xg of chromosome losses. However, a certain mutagenic effect in the pea caused by a number of metal ions was fpund by von Rosen (1964). Sterility at doses above LD50 of the mercury complexes has been recorded in barley (Ehrenberg et aLy unpublished). Scheibe (1959) found a mutagenic effect in barley and wheat of AICI3 when applied to the spike following the method of Oehlkers (1949). 

Hundreds of loci are involved in the barley chlorophyll mutation system (Gustafsson, 1955), and tests for sterility in barley, embryonic lethals in Arabidopsis, or quantitative traits in different species probably respond to mutations in thousands of loci. These tests record forward mutation independently of locus specificities inferred from variations in phenotype spectra and from mutabilities of individual genes cf. Ehrenberg et al., 1956 Lundqvist et al., 1968). 

A complete chromosome analysis of male sterility requires the examination of each of the four autosomes in all three possible combinations (m/m, a/m, a/a) and under all possible backgrounds for the other chromosomes. This clearly demands an inordinate amount of effort. As an alternative, we have examined a number of cases in which the two sex chromosomes occurred in different combinations and appeared, from the outset, to be of special interest (Zouros et al., 1988 Zouros, 1989). Males of the type Xm/Ym are mostly fertile (more acQurately, they have motile sperm sperm motility is the phenotype that we score in these experiments), except when they carry an arizonae third chromosome (i.e. when they are Xm/Ymllla/m), in which case many have immotile sperm. Males of the type Xa/Ya can be fertile or sterile depending on whether... 

Turner s Syndrome. In Turner s syndrome (XO 45 chromosomes), there is a congenital absence of the gonads, and the ovaries exist only in the form of slender streaks of connective tissue. The patients affected by the Turner syndrome are phenotypically females and have a vagina and uterus. However, at puberty they do not menstruate (amenorrhea), and their breasts never develop. Needless to say they are sterile, in contrast to XO mice, which can procreate. Without female hormones negative feedback is abolished, and, as a result, these patients excrete large amounts of gonadotropins in the urine [88, 89]. 

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