Chromosome errors in human eggs shape natural fertility over reproductive life span.

Chromosome errors, or aneuploidy, affect an exceptionally high number of human conceptions, causing pregnancy loss and congenital disorders. Here, we have followed chromosome segregation in human oocytes from females aged 9 to 43 years and report that aneuploidy follows a U-curve. Specific segregation error types show different age dependencies, providing a quantitative explanation for the U-curve.

Tripolar chromosome segregation drives the association between maternal genotype at variants spanning PLK4 and aneuploidy in human preimplantation embryos.

Aneuploidy is prevalent in human embryos and is the leading cause of pregnancy loss. Many aneuploidies arise during oogenesis, increasing with maternal age. Superimposed on these meiotic aneuploidies are frequent errors occurring during early mitotic divisions, contributing to widespread chromosomal mosaicism.

Characterization of the Escherichia coli K-12 ydhYVWXUT operon: regulation by FNR, NarL and NarP.

In Escherichia coli K-12 the expression of many genes is controlled by the oxygen-responsive transcription factor FNR and the nitrate- and nitrite-responsive two-component systems NarXL and NarPQ. Here, the ydhY gene is shown to be the first gene of a six-gene operon (ydhYVWXUT) that encodes proteins predicted to be components of an oxidoreductase. Mapping the ydhY-T transcript start and site-directed mutagenesis confirmed that the ydhY-T genes are transcribed from an FNR-dependent class II promoter and showed that the FNR site is centred at -42.