The c-mos proto-oncogene is expressed as a maternal mRNA in oocytes and early embryos of Xenopus laevis, but its translation product pp39mos is detectable only during progesterone-induced oocyte maturation. Microinjection of mos-specific antisense oligonucleotides into oocytes not only prevents expression of pp39mos, but also blocks germinal vesicle breakdown, indicating that it functions during reinitiation of meiotic division.

A new apparatus for continuously detecting fluorescently labeled DNA fragments is based on infrared fluorescence technology. This technology combines state-of-the-art developments in chemistry, laser technology, and detection, while achieving improved reliability, sensitivity, and flexibility for applications including DNA sequencing. DNA molecules labeled with a novel infrared fluorophore are detected during electrophoresis using a scanning infrared fluorescence microscope. The microscope consists of a laser diode for exciting the fluorophore and a silicon avalanche photodiode for detecting the infrared emission. Optimum conditions for detection and throughput are obtained by adjusting electrophoresis, scanning and imaging parameters. Typical DNA sequencing runs (test templates) allow identification of over 500 bases per sample with greater than 99% accuracy.

A method for sequencing DNA by using a difluoresceinated primer and laser excitation is described. Dideoxy protocols have been determined that provide sequences for 600 bases starting with base 1 with <1% error in a single load. Electrophoresis is at 20 W and the bands are detected 24 cm from the bottom of the loading well with a scanning fluorescence detector. Bands are imaged on a TV screen in two dimensions. The sequences can be read from the TV screen manually or semiautomatically by using a simple software program. The system allows more bases to be read with a lower error rate than any other reported automated sequencing method. The need for rapid, reliable automated sequencing with low cost per sequenced base has been addressed (3-7). Several automated approaches to DNA sequencing have been reported using both radioactive detection (8, 9) and fluorescent detection (10-17).The purpose of this report is to show an improved method for automated, continuous, on-line, real-time DNA sequencing (10-12). The method uses standard dideoxy reactions with a fluorescently tagged primer carrying two fluoresceins. A fluorescence detection system located at a fixed distance from the loading wells records the bands as a twodimensional image as they move past the detector. MATERIALS AND METHODS Synthesis of Fluorescently Labeled Primers. A deoxyuridineanalog with a primary amine "linker arm" of 12 atoms attached at C-5 was synthesized as published (18,19). Synthesis of the analog consists of derivatizing 2'-deoxyuridine through organometallic intermediates to give 5-(methyl propenoyl)-2'-deoxyuridine. Reaction with dimethoxytritylchloride produces the corresponding 5'-dimethoxytrityl adduct. The methyl ester is hydrolyzed, activated, and reacted with an appropriately monoacylated alkyl diamine. After purification, the resultant linker arm nucleosides are converted to nucleoside analogs suitable for chemical oligonucleotide synthesis. The structure of the linker arm analog is shown in Fig. 1 5610The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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How tyrosinase becomes associated with the premelanosomes was investigated by histochemical demonstration of tyrosinase activity by the use of dihydroxyphenylalanine (DOPA) in melanocytes of regenerating fowl feathers . The reaction product of DOPA was localized in the anastomosing membrane tubules associated with the concave side of some dictyosomes of the Golgi apparatus and in coated vesicles most of which were in connection with the dictyosomes . No reaction product was found in early premelanosomes . In premelanosomes, the reaction product of DOPA appears first in vesicles approximately 400 A in diameter which are surrounded by a matrix with a characteristic periodicity . These observations seem to allow the speculation that the coated vesicles function in the transport of tyrosinase, and that the premelanosomes are formed in a process which is not necessarily dependent on the Golgi apparatus as was assumed earlier.