| circular sulcus of insula | A saemicircular fissure demarcating the insula from the opercula above, below, and behind. Synonym: sulcus circularis insulae, circular sulcus of Reil, limiting sulcus of Reil. (05 Mar 2000) |
|---|---|
| circular sulcus of Reil | A saemicircular fissure demarcating the insula from the opercula above, below, and behind. Synonym: sulcus circularis insulae, circular sulcus of Reil, limiting sulcus of Reil. (05 Mar 2000) |
| covalently closed circular DNA | <molecular biology> A circular molecule of double-stranded DNA which is supercoiled, or coiled up on itself due to internal tensions, because there are no breaks in the phosphate backbone (upon which the nucleotide bases are mounted) to relieve the tensions and allow it to form an open circle. (09 Oct 1997) |
| DNA, circular | Any of the covalently closed DNA molecules found in bacteria, many viruses, mitochondria, plastids, and plasmids. Small, polydisperse circular DNA's have also been observed in a number of eukaryotic organisms and are suggested to have homology with chromosomal DNA and the capacity to be inserted into, and excised from, chromosomal DNA. It is a fragment of DNA formed by a process of looping out and deletion, containing a constant region of the mu heavy chain and the 3'-part of the mu switch region. Circular DNA is a normal product of rearrangement among gene segments encoding the variable regions of immunoglobulin light and heavy chains, as well as the T-cell receptor. (12 Dec 1998) |