| double back cross | A mating that is a back cross at each of two loci of interest; of special value and importance in linkage analysis. (05 Mar 2000) |
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| topping and back pressure turbine | Turbines which operate at exhaust pressure considerably higher than atmospheric (noncondensing turbines). These turbines are often multistage types with relatively high efficiency. (05 Dec 1998) |
| true muscles of back | Muscles of the back innervated by the dorsal primary rami of spinal nerves; includes erector spinae, transversospinalis, interspinal, and intertransverse muscles; excludes the superficial back muscles which are appendicular and are innervated by ventral rami, and the trapezius, innervated by the spinal accessory nerve. Synonym: true muscles of back. (05 Mar 2000) |
| fold-back elements | A type of transposable element that possesses long inverted repeats, such that when denatured, loops are formed. (05 Mar 2000) |
| low back pain | A continuous pain in the lower back or lumbar region. (12 Dec 1998) |