Lessons from mitochondrial DNA mutations.

The small, maternally inherited mitochondrial DNA (mtDNA) has turned out to be a hotbed of pathogenic mutations: 13 years into the era of "mitochondrial medicine", over 100 pathogenic point mutations and countless rearrangements have been associated with a variety of multisystemic or tissue-specific human diseases. MtDNA-related disorders can be divided into two major groups: those due to mutations in genes affecting mitochondrial protein synthesis in toto and those due to mutations in specific protein-coding genes. Pathogenesis is only partially explained by the rules of mitochondrial genetics and remains largely uncharted territory. Therapy is still woefully inadequate, but a number of promising approaches are being developed.     

Lessons from the rifamycin biosynthetic gene cluster.

There is currently intense interest in unravelling the modus operandi of type I modular polyketide synthases in order to lay the ground work for their use in the combinatorial biosynthesis of new bioactive molecules. Much of our knowledge is derived from studies on 6-deoxyerythronolide B (DEBS), the enzyme assembling the polyketide backbone of erythromycin. Work on the rifamycin polyketide synthase has revealed a number of features that differ from those seen with DEBS.     

Lessons from 1950

Second-trimester maternal serum screening is a noninvasive means of identifying pregnant women at an increased risk for various conditions including a fetus with open spina bifida, fetal Down syndrome, trisomy 18, multiple gestation, and adverse pregnancy outcome. Combinations of several different markers are available for screening. These include alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol. In this review, we discuss the benefits and limitations of the screening tests and the suggested protocols for the care of patients.     

Lessons from an audit of unplanned pregnancies.

To determine the effectiveness of contraceptive use a two year audit of pregnant women registered in one group practice was carried out. The methods of contraception used by women with unplanned pregnancies were studied and the rates of failure assessed. Of the 518 pregnancies during the study, 187 (36%) were unplanned. Unplanned pregnancies were most common in the 15-19 age group (54 out of 187), and women aged under 25 used contraceptives less reliably than women aged 25 and over. The combined pill was the most effective method of contraception in all age groups. The methods that resulted in most unplanned pregnancies were the sheath in women aged 25 and over and incorrect use of oral contraceptive or no contraception in those aged under 25. The fear of side effects was an important reason why women did not use the combined pill, being cited by 22 out of 134 women, and inappropriate medical advice was cited by a further 20 women. More discussion between doctors and patients and readily available information on the use of oral contraceptives might help to reduce the number of unplanned pregnancies.     

Mechanisms of Recombination: Lessons from E. coli

The genetics and biochemistry of genetic recombination in E. coli has been studied for over four decades and provides a useful model system to understand recombination in other organisms. Here we provide an overview of the mechanisms of recombination and how such processes contribute to DNA repair. We describe the E. coli functions that are known to contribute to these mechanisms, step by step, and summarize their biochemical properties in relation to the role these proteins play in vivo. We feature areas of investigation that are newly emerging, as well as work that provides a historical perspective to the field. Finally, we highlight some of the questions that remain unanswered.