Some simple formulae were obtained which enable us to estimate evolutionary distances in terms of the number of nucleotide substitutions (and, also, the evolutionary rates when the divergence times are known). In comparing a pair of nucleotide sequences, we distinguish two types of differences; if homologous sites are occupied by different nucleotide bases but both are purines or both pyrimidines, the difference is called type I (or “transition” type), while, if one of the two is a purine and the other is a pyrimidine, the difference is called type II (or “transversion” type). Letting P and Q be respectively the fractions of nucleotide sites showing type I and type II differences between two sequences compared, then the evolutionary distance per site is K = — (1/2) ln {(1 — 2P — Q) }. The evolutionary rate per year is then given by k = K/(2T), where T is the time since the divergence of the two sequences. If only the third codon positions are compared, the synonymous component of the evolutionary base substitutions per site is estimated by K'S = — (1/2) ln (1 — 2P — Q). Also, formulae for standard errors were obtained. Some examples were worked out using reported globin sequences to show that synonymous substitutions occur at much higher rates than amino acid-altering substitutions in evolution.

A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences.

A technique for radiolabeling DNA restriction endonuclease fragments to high specific activity

A technique for conveniently radiolabeling DNA restriction endonuclease fragments to high specific activity is described. DNA fragments are purified from agarose gels directly by ethanol precipitation and are then denatured and labeled with the large fragment of DNA polymerase I, using random oligonucleotides as primers. Over 70% of the precursor triphosphate is routinely incorporated into complementary DNA, and specific activities of over 10(9) dpm/microgram of DNA can be obtained using relatively small amounts of precursor. These "oligolabeled" DNA fragments serve as efficient probes in filter hybridization experiments.

We describe a new basis for the construction of a genetic linkage map of the human genome. The basic principle of the mapping scheme is to develop, by recombinant DNA techniques, random single-copy DNA probes capable of detecting DNA sequence polymorphisms, when hybridized to restriction digests of an individual's DNA. Each of these probes will define a locus. Loci can be expanded or contracted to include more or less polymorphism by further application of recombinant DNA technology. Suitably polymorphic loci can be tested for linkage relationships in human pedigrees by established methods; and loci can be arranged into linkage groups to form a true genetic map of "DNA marker loci." Pedigrees in which inherited traits are known to be segregating can then be analyzed, making possible the mapping of the gene(s) responsible for the trait with respect to the DNA marker loci, without requiring direct access to a specified gene's DNA. For inherited diseases mapped in this way, linked DNA marker loci can be used predictively for genetic counseling.

Construction of a genetic linkage map in man using restriction fragment length polymorphisms.

The pUC plasmids, an M13mp7-derived system for insertion mutagenesis and sequencing with synthetic universal primers.

Mice carrying null mutations of the genes encoding insulin-like growth factor I (Igf-1) and type 1 IGF receptor (Igf1r)

https://www.cell.com/cell/pdf/S0092-8674(05)80085-6.pdf

Role of Insulin-like Growth Factors in Embryonic and Postnatal Growth

Parental imprinting of the mouse insulin-like growth factor II gene

Growth factors are thought to function as pivotal autocrine-paracrine regulatory signals during embryonic development. Insulin-like growth factor II (IGF-II), a mitogenic polypeptide for a variety of cell lines, could have such a role, as indicated by the pattern of expression of its gene during rodent development. The IGF-II gene uses at least three promoters and expresses several transcripts in many tissues during the embryonic and neonatal periods, whereas expression in adult animals is confined to the choroid plexus and the leptomeninges. To examine the developmental role of IGF-II, we have begun to study the consequences of introducing mutations at the IGF-II gene locus in the mouse germ line. We have disrupted one of the IGF-II alleles in cultured mouse embryonic stem (ES) cells by gene targeting and constructed chimaeric animals. Germ-line transmission of the inactivated IGF-II gene from male chimaeras yielded heterozygous progeny that were smaller than their ES cell-derived wild-type littermates (about 60% of normal body weight). These growth-deficient animals were otherwise apparently normal and fertile. The effect of the mutation was exerted during the embryonic period. These results provide the first direct evidence for a physiological role of IGF-II in embryonic growth.

A growth-deficiency phenotype in heterozygous mice carrying an insulin-like growth factor II gene disrupted by targeting.

https://www.cell.com/cell/pdf/0092-8674(78)90036-3.pdf

Argiris Efstratiadis

Papers

Mice carrying null mutations of the genes encoding insulin-like growth factor I (Igf-1) and type 1 IGF receptor (Igf1r)

Role of Insulin-like Growth Factors in Embryonic and Postnatal Growth

Parental imprinting of the mouse insulin-like growth factor II gene

A growth-deficiency phenotype in heterozygous mice carrying an insulin-like growth factor II gene disrupted by targeting.

The isolation of structural genes from libraries of eucaryotic DNA