Insertion of an Alu Element in Thyroglobulin Gene as a Novel Cause of Congenital Hypothyroidism.

The thyroglobulin (TG) gene encodes a protein required for thyroid hormone synthesis and iodine storage. Deleterious TG mutations produce congenital hypothyroidism (CH) often presenting with undetectable serum TG. Alu elements, common throughout the human genome, have a poly(dA) region in the 3' end of the strand. Herein two of four siblings of a consanguineous Sudanese family with CH, goiter, high initial serum thyrotropin, and undetectable TG were found to have a novel frameshift insertion of an Alu element within an exon of the TG gene: c.7909ins p.Y3637Ffs. This report demonstrates a novel Alu element insertion within TG causing CH.

Martynas Ycas: The "Archivist" of the RNA Tie Club.

Between about 1951 and the early 1960s, the basic structure of molecular biology was revealed. Central to our understanding was the unraveling of the various roles of RNA, culminating in the identification of messenger RNA (mRNA) and the deciphering of the genetic code. We know a great deal about the role of Brenner, Crick, Jacob, and Nirenberg in these discoveries, but many others played important supporting parts. One of these is a little-known scientist, Martynas Ycas, who appears in histories, generally without explanation, as the "archivist of the RNA Tie Club." Ycas was born in Lithuania. His father helped write the Lithuanian Constitution in 1919. He studied Roman Law and served in the Lithuanian army before escaping from the Russians in 1940. The records of correspondence of Ycas with the physicist George Gamow and with Francis Crick throw some light on the genesis of our understanding of the role of mRNA. The story of the "RNA Tie Club" illustrates the difficulty in assigning credit for important discoveries and underscores the importance of a free exchange of information, even (or especially) among competitors.

Why Is DNA Double Stranded? The Discovery of DNA Excision Repair Mechanisms.

The persistence of hereditary traits over many generations testifies to the stability of the genetic material. Although the Watson-Crick structure for DNA provided a simple and elegant mechanism for replication, some elementary calculations implied that mistakes due to tautomeric shifts would introduce too many errors to permit this stability. It seemed evident that some additional mechanism(s) to correct such errors must be required. This essay traces the early development of our understanding of such mechanisms. Their key feature is the cutting out of a section of the strand of DNA in which the errors or damage resided, and its replacement by a localized synthesis using the undamaged strand as a template. To the surprise of some of the founders of molecular biology, this understanding derives in large part from studies in radiation biology, a field then considered by many to be irrelevant to studies of gene structure and function. Furthermore, genetic studies suggesting mechanisms of mismatch correction were ignored for almost a decade by biochemists unacquainted or uneasy with the power of such analysis. The collective body of results shows that the double-stranded structure of DNA is critical not only for replication but also as a scaffold for the correction of errors and the removal of damage to DNA. As additional discoveries were made, it became clear that the mechanisms for the repair of damage were involved not only in maintaining the stability of the genetic material but also in a variety of biological phenomena for increasing diversity, from genetic recombination to the immune response.

A Physicist's Quest in Biology: Max Delbrück and "Complementarity".

Max Delbrück was trained as a physicist but made his major contribution in biology and ultimately shared a Nobel Prize in Physiology or Medicine. He was the acknowledged leader of the founders of molecular biology, yet he failed to achieve his key scientific goals. His ultimate scientific aim was to find evidence for physical laws unique to biology: so-called "complementarity." He never did. The specific problem he initially wanted to solve was the nature of biological replication but the discovery of the mechanism of replication was made by others, in large part because of his disdain for the details of biochemistry. His later career was spent investigating the effect of light on the fungus Phycomyces, a topic that turned out to be of limited general interest. He was known both for his informality but also for his legendary displays of devastating criticism. His life and that of some of his closest colleagues was acted out against a background of a world in conflict. This essay describes the man and his career and searches for an explanation of his profound influence.

Genetic counseling for thalassemia in the Islamic Republic of Iran.

The response of groups to pressing medical problems cannot be predicted on theoretical grounds. An example is the program for the control of beta-thalassemia in Iran, a country with a tradition of inbreeding and a conservative religious culture, and in which thalassemia is common. Thalassemia is largely treatable, but the treatment is lifelong and onerous and creates a serious economic burden for the individual family and for the national health budget. The genetics are simple, and inexpensive screening tests are available to identify carriers. An Iranian program requiring mandatory premarital screening was started in 1997, and between 1998 and 2005 the laws of the country were modified to permit abortion of affected fetuses. The story of this effort indicates how a country with a social system very different from that of the United States responded to a medical problem with significant ethical overtones. The Iranian experience supports the optimistic view that societies can react to pressing problems with pragmatic rather than theoretical solutions.

PubMed, the New York Times and the Chicago Tribune as tools for teaching genetics.

An elementary course in human heredity for students not planning to major in the sciences can be based on current scientific literature and on the popular media. Examinations are constructed from questions on recent abstracts obtained from PubMed. The course is designed to promote writing skills in the sciences, and students write two papers in the course of a quarter. In the first paper, students trace the primary source of media reports on genetics and attempt to evaluate the reporter's translation. In a second paper, students write popular articles on the basis of current primary sources.

Getting around.

This essay is a response to a request from the Editor for a "historical reflection" relating to work on DNA repair from my laboratory. The writing has been an interesting exercise since it made me recall the people I have worked with and some of the things we found and the many we missed. In the course of the writing, an article was published in The New York Review of Books, which argued that there is a "pervasive dishonesty in the practice of science" relating to the authorship of scientific papers. It seemed to me that the events I was relating spoke to that charge and I appreciate the opportunity to comment.

The "A" rule revisited: polymerases as determinants of mutational specificity.

Organisms control the specificity and frequency with which they mutate via their complement of proteins. The mismatch repair (MMR) proteins correct errors after they are made. The DNA polymerases of the cell determine the response to damaged DNA which has not been repaired by excision. Polymerase action can be considered as consisting of three main steps: addition of a base, proofreading of the added nucleotide and elongation. Each of these steps is kinetically complex and can be modulated. The modulation accounts for different behaviors of organisms in response to stress. The recent findings of DNA polymerases with properties appropriate for dealing with damaged DNA may help to account for the phenomenon of spontaneous mutation and for the hypermutability associated with immunoglobulin maturation and carcinogenesis.