- 1. The process with which foreign DNA that has been introduced into a prokaryotic cell becomes ineffective. 2. A limitation.- asymmetric fetal growth r. normal fetal head size as a result of preferential shunting of blood to brain, and decreased abdominal circumference from decreased adipose tissue and liver size; probably caused by placental insufficiency.- fetal growth r. fetal weight ≤5th percentile for gestational age. SYN: intrauterine growth retardation.- lactase r. an inherited trait in which there is low lactase activity and thus there is defective lactose intestinal metabolism. Cf.:lactase persistence.- MHC r. T helper cells only recognize an antigen that is presented with class II major histocompatibility antigens whereas T cytotoxic cells usually only recognize a processed antigen in conjunction with class I major histocompatibility antigens.- symmetric fetal growth r. proportional reduction in fetal head and body size, commonly constitutional or caused by an early intrauterine insult such as infection.
* * *re·stric·tion ri-'strik-shən n, often attrib the breaking of double-stranded DNA into fragments by restriction enzymes <\restriction sites>
* * *re·stric·tion (re-strikґshən) 1. a limitation. 2. a thing or process that limits.
Medical dictionary. 2011.