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PubMed1995

Inheritance of migraine investigated by complex segregation analysis.

Migraine is the most common neurological disorder, affecting about 20% of adults. The mode of inheritance was analyzed in the two main types of migraine, migraine without aura (MO) and migraine with aura (MA), by complex segregation analysis using the computer program POINTER. We included 126 probands with MO and 127 probands with MA from the general population. First-degree relatives and spouses were blindly interviewed by a neurological research fellow. The complex segregation analysis indicated that both MO and MA have multifactorial inheritance without generational difference.

Adolescent↗
PubMedDate not supplied

Commingling and segregation analysis of serum uric acid in five North American populations: the Lipid Research Clinics family study.

The role of major genes in the expression of serum uric acid (UA) levels was investigated in data collected from five clinics of the Lipid Research Clinics (LRC) family study. Over 2,000 randomly ascertained individuals were analyzed. The UA distributions were homogeneous among the five LRC clinics and between the parental and offspring generations. This result suggested that the data could be pooled across clinics, thereby increasing the statistical power associated with larger sample sizes for testing various null hypotheses. Additionally, a mixture of three normal distributions best characterized the combined-clinics data. Segregation patterns were examined in the untransformed data, as well as in a more conservative (and biologically meaningful) log transformation. Prior to log transformation, both major and multifactorial effects were detected. The major effect was not transmissible, i.e., was not compatible with Mendelian transmission, and accounted for 39% of the variance in UA levels. However, after the log transform was applied to the data and the segregation analysis was repeated, support for the major effect disappeared altogether and only the multifactorial component remained, accounting for 50% of the variation in offspring and 19% in patients.

Adolescent↗
PubMed1990

Segregation analysis of 1885 DMD families: significant departure from the expected proportion of sporadic cases.

The proportion of sporadic cases of Duchenne muscular dystrophy has been estimated by classical segregation analysis in a pooled sample of 1885 sibships from 7 different countries. A significant departure from the theoretical expectations based on mutation-selection equilibrium is observed (segregation frequency = 0.439 +/- 0.017; frequency of sporadic cases = 0.229 +/- 0.026, at the maximum likelihood). The occurrence of germinal mosaicism in some of the mothers of Duchenne cases may account for this peculiar finding, although a possible role of inequality of mutation rates in the two sexes cannot be ruled out.

Chromosomes, Human↗
PubMed1992

Fragile site (16) (q22). III. Segregation analysis.

The rare autosomal fragile site, fra (16) (q22), is the most common of all rare autosomal fragile sites and has a heterozygote frequency of about 5%. Evidence for it was found following the segregation expected from a simple codominant trait with complete penetrance; this is in contrast to a variety of other rare autosomal fragile sites. Based on the analysis of 12 families in which fra (16) (q22) is segregating, we found that, whereas complete penetrance could be confirmed, the transmitting parent was significantly more likely to be of the female sex. On the other hand, there was no evidence for preferential transmission to offspring of either sex.

Chromosome Fragile Sites↗
PubMed1990

The segregation distortion (SD) phenomenon in wild populations of Drosophila melanogaster: interaction between chromosomes 3 and SD chromosomes 2.

The Segregation Distortion (SD) phenomenon is a typical case of non-Mendelian segregation in Drosophila melanogaster, due to the dysfunction of sperm bearing a non-SD homologous chromosome. In nature, several factors involved in the expression of the SD phenomenon have been described; among these, a genetic modifier carried by chromosome 3, which enhances the distortion effect of the SD chromosomes. The analysis of natural Sardinian populations, carried out in order to evaluate the presence of chromosome 3 bearing these enhancer factors, has enabled us to ascertain that (a) also in these populations chromosomes 3 with enhancer factors are present, although with frequencies lower than those previously reported in other publications; (b) among these enhancer chromosomes 3, some increase the k of certain chromosomes 2 from values of chromosomes considered non-distorting (k less than or equal to 0.66) to value typical of SD chromosomes. The data obtained also allow us to put forward some considerations regarding the dynamics of the SD phenomenon in Sardinian populations, where the frequency of SD chromosomes is fairly elevated.

Animals↗
PubMed1981

Duplication deficiency as the result of meiotic segregation of a maternal InV (10).

In a family a large pericentric inversion involving nearly 70% of the chromosome 10 has been segregating during three generations, giving several carriers and an affected male with the karyotype 46,XY,der(10)(10pter Leads to 10q25::10p12 Leads to 10pter)mat. The patient is trisomic for 10p except for a small segment near the centromere, and monosomic for the distal 10q26. A simple diagrammatic representation explains the behavior of the inv(10) in meiosis. The study of meiotic segregation in the present case, and the reviews of previously reported duplication-deficiencies, agree with established postulates and add some principles to the understanding of duplication deficiencies resulting from the meiotic behavior of inverted chromosomes.

Adult↗
PubMed1977

Risk for short arm 10 trisomy. A segregation analysis of eleven families with different translocations.

A segregation analysis has been carried out for 11 families with trisomy 10p caused by familial translocations involving a segment of the short arm of chromosome 10. The theoretical basis for the analysis is considered in some detail. No differences were found between the segregation pattern in the offspring of carrier mothers and that of carrier fathers. There was a high risk for offspring with trisomy 10p (22%). A phenotypically normal descendant also has a high risk of becoming a balanced translocation carrier (71%). This result does not deviate significantly from the theoretical value of 50%.

Chromosomes, Human, 6-12 and X↗
PubMed1984

Segregation of HLA-DR2 among affected and non-affected offspring of 66 families with type 1 (insulin-dependent) diabetes.

Segregation of HLA-DR2 among affected and unaffected offspring was studied in 66 HLA-genotypes families with Type 1 diabetes in whom at least one parent carried DR2. The frequency of DR2-positive parents (21%) was not different from that of control families (29%). Among the diabetic probands, the gene frequency of DR2 was significantly decreased compared with control subjects (0.05 versus 0.17, p less than 0.001) as were DR5 (0.07 versus 0.17, p less than 0.01) and DR7 (0.06 versus 0.13, p less than 0.003). Twenty probands carried DR2, in 11 or whom (55%) it was found in combination with either DR3 or DR4. The nine cases who carried another DR allele included one who was DR2 homozygous. Transmission of DR2 was reduced in affected offspring, and random in unaffected siblings, compared with the expected ratio. However, when the DR2 transmission was analysed separately for parents bearing DR2 with DR3, DR4 or another DR allele, it appeared that DR2 transmission to affected offspring was random when the parents carried neither DR3 or DR4, the transmission deficit being due to over-transmission of DR3 and DR4. The haplotype analysis showed that the haplotype A3, Cw7, B7, GfS, DR2, found in 19% of "non-diabetic" DR2 haplotypes was practically absent among "diabetic" DR2-haplotypes (4%). In conclusion, population and segregation analysis could not demonstrate a specific protective effect of DR2.

Diabetes Mellitus, Type 1↗
PubMed1985

Segregation analysis of a marker localised Xp21.2-Xp21.3 in Duchenne and Becker muscular dystrophy families.

A DNA marker C7, localised Xp21.1-Xp21.3, has been studied in kindreds segregating for Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD). In DMD families four crossovers were observed in 38 informative meioses between C7 and the DMD locus (theta = 0.12, z max = +2.72). In BMD families no recombinants were observed in the 16 informative meioses studied. These data are consistent with the localisation of the mutations in these disorders being in the same region of Xp21. Studies in families also segregating for the DNA marker 754 support the previously reported physical order of these loci as X centromere-754-DMD-BMD-C7-X telomere. A recombination fraction of 0.11 (z max = +5.58) was found between DMD-754 by combining our previously published data with the data presented here. C7 and 754 thus provide good bridging markers for the diagnosis of DMD and BMD.

Chromosome Banding↗
PubMed1987

Sporadic cases in Duchenne muscular dystrophy. A reappraisal through segregation analysis on 988 sibships.

A new estimation of the proportion of sporadic cases in Duchenne muscular dystrophy was attempted by means of segregation analysis in a sample of 988 sibships collected on a world-wide scale by different authors. Maximum likelihood estimates of ascertainment probability (pi), segregation frequency (p), and frequency of sporadic cases (x) were calculated by Morton's equations under different hypotheses. The best fit was found for p = 0.454 +/- 0.024 and x = 0.235 +/- 0.034. The possibility that the proportion of sporadic cases might be lower than the expected 1/3 is suggested.

Gene Frequency↗
PubMed1989

Segregation frequency in microcephaly.

A total of 118 cases of microcephaly were clinically evaluated under two main groups: primary microcephaly (61 cases) and secondary microcephaly (57 cases). Secondary cases were generally characterized by convulsions, spasticity, and other congenital anomalies. Estimates of segregation frequency obtained separately in primary and secondary cases indicated that the primary consanguineous cases were most probably due to a single recessive gene. The segregation frequency was substantially less in other types, indicating much lower genetic risks in these cases.

Consanguinity↗
PubMed1981

XY gonadal dysgenesis: genetic heterogeneity based upon clinical observations, H-Y antigen status and segregation analysis.

Clinical observations and segregation analysis indicate that XY gonadal dysgenesis is characterized by genetic heterogeneity. In addition to the type inherited in X-linked recessive fashion, segregation analysis of other families suggested another type by revealing that the proportion of affected sibs did not differ from that expected on the basis of a male-limited autosomal recessive inheritance. Further heterogeneity may be deduced on the basis of coexisting campomelic dwarfism or possibly also renal parenchymal abnormalities. These observations of genetic heterogeneity must be considered when interpreting studies in which individuals with XY gonadal dysgenesis may or may not show H-Y antigen.

Alleles↗
PubMed1989

Human BF*F-subtypes: segregation analysis with inclusion of MHC haplotypes.

The segregation of factor B(BF)F subtypes was analyzed in conjunction with other MHC markers in 15 families with 89 offspring. Informative data for BF F subtypes were obtained from 11 families, 6 of them with known recombinant individuals for the HLA-B/DR/GLO region. The subtypes did not contribute further to the localization of the cross-overs, but followed the known segregation of conventional BF allotypes. In 2 families of one kinship, the recognition of heterozygous BF*FAFB individuals could be established following the inclusion of three generations. The rarer of the two BF F subtype alleles, BF*FA, is positively associated with the HLA haplotypes BW62, CW3, C4A*3 and A29, CWX, B44, C4A*3, B*1, DR7. BF F subtypes are regarded as a very useful additional tool for studies of MHC organization and disease association.

Alleles↗
PubMed1975

Segregational mechanisms of sex chromosomes in Spongilla-flies (Neuroptera: Sisyridae).

Evolutionary loss of the Y chromosome has occurred in Climacia areolaris (Hagen) of the neuropteran family Sisyridae. The diploid set comprises 6 pairs of autosomes, plus 2 X chromosomes in the female and 1 X in the male. The Y is retained in Sisyra vicaria (Walker) of the same family: its chromosome number is 14 in both sexes including 2X chromosomes in the female and 1X plus Y in the male. Two alternative pathways for the segregation of the sex chromosomes-distance segregation and sex bivalent formation-co-exist in the latter species in a ratio of approximately 1 to 6; the possible phylogenetic significance of this feature is discussed.

Animals↗
PubMed1987

Centromeric proteins recognized by CREST sera and meiotic chromosome segregation.

Analysis of the peptides recognized by CREST sera was carried out in different mouse tissues and cells, including spermatozoa. In all cases, a polypeptide of Mr = 18,000 was recognized by the sera and occasionally two other proteins of Mr = 80,000 and Mr = 140,000 were observed after immunoblotting of nuclear proteins. In both early and late spermatids, centromeric staining was observed after incubation and immunofluorescence with CREST sera. After detergent treatment, it was even possible to detect centromeric staining in mature spermatozoa. In spermatid cells, the immunofluorescent pattern presented a binomial distribution of the number of fluorescent spots, with a mean value around half of the haploid number of chromosomes. Since this pattern is the result of chromosome segregation after meiosis II, our data suggest that this centromeric peptide is not directly implicated in the chromosome segregation process. On the other hand, the distribution of spots after immunofluorescence suggests a different organization of centromeric components in meiosis I and meiosis II.

Animals↗
PubMed1989

Linkage disequilibrium and CF allele segregation analysis in cystic fibrosis families in Northern Ireland.

Linkage disequilibrium and cystic fibrosis (CF) allele segregation were analysed in 46 CF families in Northern Ireland. The smaller (+) allele of the KM19/PstI polymorphism and the larger (-) allele of the XV-2c/TaqI polymorphism showed marked linkage disequilibrium with CF. This information can be used to alter the risk of an individual being a carrier of CF away from the expected population risk of 1 in 20. The high-risk genotypes K+K+ or X-X- have a risk of 1 in 10 and the low-risk genotypes K-K- or X+X+ have a risk of 1 in 50. A study of the segregation of CF alleles in the 46 families, using KM19 and Xv-2c, showed preferential inheritance of the paternal (79%), as opposed to the maternal (21%), CF allele by the heterozygous carriers. A mechanism that might explain this observation is discussed.

Alleles↗
PubMed1985

Further segregation analysis of the fragile X syndrome with special reference to transmitting males.

A new series of 96 pedigrees with the fra(X) syndrome was analysed using complex segregation analysis with pointers, defining affection as any degree of mental impairment. These families were found to exhibit the same segregation pattern as the first series of 110 pedigrees (Sherman et al. 1984). The best estimate for penetrance of mental impairment in males was 79% and in females was 35% for the combined data. Again, there was little evidence for sporadic cases among affected males. Many more intellectually normal transmitting males have been observed since the existence of such males and the concomitant need to investigate the paternal side of pedigrees was recognized. On further investigation of all 206 pedigrees from the old and new data sets, the sibships of nonexpressing males appeared to be different from those of expressing males. Our analysis, using mental impairment as the phenotype, suggested that obligate carrier mothers and daughters of intellectually normal transmitting males are rarely, if ever, mentally impaired and that the sibs of transmitting males are much less likely to be retarded than the sibs of mentally impaired males. Though mothers and daughters of transmitting males are similar in phenotype, the expression of the gene in their offspring appears to be different: the penetrance of mental impairment is higher in offspring of intellectually normal daughters of transmitting males than in offspring of intellectually normal mothers of transmitting males. The implications of these observations for genetic counseling and for genetic models of the fra(X) syndrome are discussed.

Female↗
PubMed1987

Chromosome segregation at meiosis I in female T(2;4)1Gö/+ mice: no evidence for a decreased crossover frequency with maternal age.

The influence of age and hormones on chromosome segregation at meiosis I was studied in female mice heterozygous for the T(2;4)1Gö translocation. Females of two age groups (18-22 and 40-56 weeks old) were stimulated for ovulation with different doses of gonadotropins (1.5 IU PMS/1.0 IU HCG or 10 IU PMS/10 IU HCG). Analysis of metaphase II oocytes revealed the highest level of hyperhaploidy (1.8%) and presegregation (4.4%) in the young females receiving the low dose. Presegregation preferentially affected the small 4(2) marker chromosome. There was no significant interference of the tetravalent with disjunction of the nontranslocated normal bivalents. Moreover, no remarkable difference in the mode of segregation (adjacent I, II or alternate) was observed. Recombination within the interstitial pairing segments of the chromosomes involved in the translocation allowed us to calculate cross-over frequencies in ovulated oocytes. For both the large 2(4) and the small 4(2) marker chromosomes, this frequency was higher in old than in young T(2;4)1Gö/+ females. Our data do not support the production line hypothesis of Henderson and Edwards (1968) which claims that chiasma frequency in oocytes decreases with maternal age.

Aging↗