DNA methylation profiles of human active and inactive X chromosomes.

X-chromosome inactivation (XCI) is a dosage compensation mechanism that silences the majority of genes on one X chromosome in each female cell. To characterize epigenetic changes that accompany this process, we measured DNA methylation levels in 45,X patients carrying a single active X chromosome (X(a)), and in normal females, who carry one X(a) and one inactive X (X(i)). Methylated DNA was immunoprecipitated and hybridized to high-density oligonucleotide arrays covering the X chromosome, generating epigenetic profiles of active and inactive X chromosomes. We observed that XCI is accompanied by changes in DNA methylation specifically at CpG islands (CGIs). While the majority of CGIs show increased methylation levels on the X(i), XCI actually results in significant reductions in methylation at 7% of CGIs. Both intra- and inter-genic CGIs undergo epigenetic modification, with the biggest increase in methylation occurring at the promoters of genes silenced by XCI. In contrast, genes escaping XCI generally have low levels of promoter methylation, while genes that show inter-individual variation in silencing show intermediate increases in methylation. Thus, promoter methylation and susceptibility to XCI are correlated. We also observed a global correlation between CGI methylation and the evolutionary age of X-chromosome strata, and that genes escaping XCI show increased methylation within gene bodies. We used our epigenetic map to predict 26 novel genes escaping XCI, and searched for parent-of-origin-specific methylation differences, but found no evidence to support imprinting on the human X chromosome. Our study provides a detailed analysis of the epigenetic profile of active and inactive X chromosomes.

Microsatellite variation reveals low genetic subdivision in a chromosome race of Sorex araneus (Mammalia, Insectivora)

Two hundred and forty-five individuals of the common shrew (Sorex araneus, Insectivora, Mammalia) from 24 sampling localities situated in four different valleys of the western European Alps were genotyped for six microsatellite loci. Allelic variability ranged from 3 to 32 different alleles at a single locus and the average gene diversity over all loci was 0.69. An analysis for F and R statistics revealed weak genetic population subdivision (Fst = 0.032; Rst = 0.016). This suggests considerable gene flow and little phylogeographic structure within and between valleys. We tested whether a stepwise mutation model (SMM) better explained variation at the microsatellite loci than an infinite allele model (IAM). No trend in favor of either model was detected.

State of Iowa Transportation Map, 1952

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1953

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1954

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1955

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1956

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1957

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1958

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1959

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1960

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1961

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.

State of Iowa Transportation Map, 1962

This document is the State Map of Iowa, both front and back of the year in the title. All maps were are in pdf format and can be used as a historical reference.