A chemically-defined medium for production of compactin by Penicillium citrinum

A mutant strain of Penicillium citrinum grown in a chemically-defined production medium, yielded 145 mg compactin l^–1. The medium also facilitated spectrophotometric analysis of compactin. Addition of KH₂PO₄in the production medium did not increase the compactin production, while addition of a surfactant, Tween 80, increased compactin to 175 mg l^–1. Inoculation with 10⁷ spores ml^–1 and initial pH of 6.5–7 were the most suitable for compactin production.     

DSLINK: a computer program for gene-centromere linkage analysis in families with a trisomic offspring.

Trisomic individuals provide information for gene-centromere mapping, since two of the four chromatids in a meiotic tetrad can be recovered. When centromeric markers are available, linkage analysis between the centromere and any marker locus can be performed in nuclear families having one or more trisomic offspring. Since conventional linkage programs consider only disomic individuals, we have written a FORTRAN computer program, DSLINK, that performs gene-centromere linkage analysis on the basis of information on trisomic and disomic offspring. This program makes it possible to study the relationship between recombination and chromosome segregation.     

Methods for studying recombination on chromosomes that undergo nondisjunction

A lod score method is provided for mapping genes relative to the centromere using family data from autosomal trisomies. Such gene-centromere mapping can be performed whenever two or more members of a meiotic tetrad can be recovered. The critical mapping parameter is not the recombination value theta or the map distance omega, but the probability of nonreduction in a heterozygous host, the probability of heterozygosity (nonreduction) is 1-gamma/2 for a meiosis I error and gamma for a meiosis II error. Under various assumptions regarding chiasma interference, gamma can be related to theta and omega. We provide specific methods for estimating gamma and theta from trisomy data using maximum likelihood, so that recombination may be studied on chromosomes that underwent nondisjunction.     

Polymorphic DNA haplotypes at the LDL receptor locus.

Mutations in the low-density lipoprotein (LDL) receptor gene result in the autosomal dominant disorder familial hypercholesterolemia (FH). Many different LDL receptor mutations have been identified and characterized, demonstrating a high degree of allelic heterogeneity at this locus. The ability to identify mutant LDL receptor genes for prenatal diagnosis of homozygous FH or to study the role of the LDL receptor gene in polygenic hypercholesterolemia requires the use of closely linked RFLPs. In the present study we used 10 different RFLPs, including three newly described polymorphisms, to construct 123 independent haplotypes from 20 Caucasian American pedigrees. Our sample contained 31 different haplotypes varying in frequency from 0.8% to 29.3%; the five most common haplotypes account for 67.5% of the sample. The heterozygosity and PIC of each site were determined, and these values disclosed that eight of the RFLPs were substantially polymorphic. Linkage-disequilibrium analysis of the haplotype data revealed strong nonrandom associations among all 10 RFLPs, especially among those sites clustered in the 3' region of the gene. Evolutionary analysis suggests the occurrence of both mutational and recombinational events in the generation of the observed haplotypes. A strategy for haplotype analysis of the LDL receptor gene in individuals of Caucasian American descent is presented.     

The probability of detecting the origin of nondisjunction of autosomal trisomies.

For studying the biology of autosomal trisomies it is necessary to establish the parental origin and meiotic stage of nondisjunction by using genetic markers. Theoretical formulas are obtained for calculating the probability of establishing (1) parental origin and meiotic stage of nondisjunction by using a centromeric marker, (2) parental origin of nondisjunction by using a noncentromeric marker, and (3) meiotic stage, given parental origin of nondisjunction. These theoretical calculations demonstrate that parental origin of nondisjunction can be identified with virtual certainty by utilizing multiple genetic markers along a chromosome arm. Centromeric markers are by themselves inefficient for determining meiotic stage of the error, but the efficiency can be considerably increased if parental origin is known with certainty. Even then, multiple centromeric markers may be necessary.     

Cloning and linkage mapping of three polymorphic tetranucleotide (TAAA)n repeats on human chromosome 21.

We report the cloning, sequencing, and mapping of three short sequence repeat polymorphisms due to tetranucleotide (TAAA)n repeats from human chromosome 21. These DNA markers (D21S221, D21S225, D21S226) have been cloned from the chromosome 21-specific plasmid library of J. C. Fuscoe, C. C. Collins, D. Pinkel, and J. W. Gray (1989, Genomics 5: 100-109) and were shown to be polymorphic by polymerase chain reaction amplification and polyacrylamide gel electrophoresis. Genotypes were determined in informative CEPH pedigrees and used in linkage analysis relative to other mapped markers on human chromosome 21. One of these markers, D21S221, is closely linked to the amyloid precursor protein gene (APP), which has been implicated in the etiology of familial Alzheimer disease in some families.     

Information content of the Centre d'Etude du Polymorphisme Humain (CEPH) family structures for linkage studies

Summary This paper derives theoretical values for joint polymorphism information content for two markers from a family structure consisting of four grandparents, two parents, and many offspring. These data determine the efficiency of linkage map construction.     

Cutaneous malignant melanoma and familial dysplastic nevi: evidence for autosomal dominance and pleiotropy.

Segregation of familial cutaneous melanoma has been shown to be compatible with autosomal dominant transmission with incomplete penetrance. However, the combined phenotype of melanoma and a known melanoma-precursor lesion, the dysplastic nevus (DN), has not previously been found to fit a Mendelian model of inheritance using complex segregation analysis. Employing a life-table and disease-free survival analysis approach, we estimated the lifetime incidence of melanoma in the sibs and offspring of DN-affected individuals to be 46%, consistent with a highly penetrant, autosomal dominant mode of inheritance. To further elucidate the relationship between the two traits, we conducted a linkage analysis between the melanoma locus and a hypothetical DN locus, and obtained a maximum lod score of 3.857 at theta = .08. Furthermore, all families giving evidence for linkage were in the coupling phase and the maximum likelihood estimate of theta was not significantly different from 0 (P = .1). This provides evidence that the DN and melanoma traits may represent pleiotropic effects of a single, highly penetrant gene behaving in an autosomal dominant manner.     

Relationship between cellular RecA protein concentration and untargeted mutagenesis in Escherichia coli

We measured the production of untargeted mutations in the cI and cII genes of untreated λ phage undergoing a lytic cycle in UV-irradiated bacterial hosts. As previously shown, treatment with 4 μg/ml of rifampicin during post-irradiation incubation inhibited amplification of the RecA protein in these cells. In addition, we observed a decreased mutation rate compared to the untreated, irradiated bacteria. Treatment with 4 μg/ml or 8 μg/ml rifampicin did not prevent the UV induction of the umuDC operon, as judged by assay of β-galactosidase activity in a umuC-lacZ fusion strain. In contrast, the UV-induction of β-galactosidase in the sulA-lacZ fusion strain was decreased by 4 μg/ml rifampicin. The inhibition of untargeted mutagenesis by this drug treatment was also observed in a strain constitutive for SOS functions (lexA (Def)) as well as ina RecA-overproducing plasmid strain, that blocks induction of heat-shock proteins, factor(s) in wild-type recA⁺ cells. An htpR165-carrying strain, that blocks induction of heat-shock proteins, exhibited normal UV-promoted mutagenesis. A correlation was observed between the cellular concentration of RecA protein, increased spontaneously by a temperature shift in a lexA(Ts) strain, and the extent of UV-promoted untargeted mutagenesis. These results suggest a mechanistic role of RecA protein in this process.