A white girl presented at age 16 yr with delayed puberty and primary amenorrhea. She had 46 chromosomes with a de novo reciprocal X;9 translocation. The normal X chromosome was found to be heterochromatic, thus preserving the function of the translocation portion of the 9. Her total estrogen and serum estradiol levels were low and her serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were at the lower end of the normal adult range. She had a reasonably good FSH and LH response to GnRH, but an inadequate response to 100 mg of clomiphene daily for 1 wk. This would suggest that the abnormality of function is probably hypothalamic, a hitherto unreported association. De novo translocations between X chromosomes and autosomes are rare and none identical to this case has been described. The breakpoint of the X chromosome was at p22, well outside the "critical region" for female reproductive function. It seems probable that her chromosome abnormality is responsible for her clinical state.

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Formaldehyde treatment of Escherichia coli curves, and polarization of fluorescence thermal profiles B transfer ribonucleic acid (tRNA) appreciably changes indicate that (1) Watson-Crick hydrogen bonding hydrodynamic and optical properties. The increase is a determinant in the configuration and helix-coil in intrinsic viscosity, decrease in sedimentation coeffi-transition of native E. coli tRNA and (2) base stacking cient coupled with the change in absorbance melting contributes to the helical rigidity in native tRNA.

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