| identical twins | Identical twins, twins which are the result of a single zygote (fertilized egg) splitting into two cell masses and becoming two individuals. The twins are genetically identical and are always of the same sex (both males or both females). Compare: dizygotic twins. (09 Oct 1997) |
|---|---|
| incomplete conjoined twins | Conjoined twin's, the two components of which equal one another but are less than entire individuals. Monoamniotic twins, twin's within a common amnion; such twin's are monovular in origin and may be conjoined. (05 Mar 2000) |
| enzygotic twins | Synonym: monozygotic twins. (05 Mar 2000) |
| twins, dizygotic | Two offspring produced in the same pregnancy from separate ova fertilised at the same time. (12 Dec 1998) |
| twins, monozygotic | Two offspring developed from one fertilised ovum. (12 Dec 1998) |
| uniovular twins | Identical twins, twins which are the result of a single zygote (fertilized egg) splitting into two cell masses and becoming two individuals. The twins are genetically identical and are always of the same sex (both males or both females). Compare: dizygotic twins. (09 Oct 1997) |
| fraternal twins | Fraternal twins are siblings who have shared a common uterine environment. They are due to fertilization of two different ova by different sperm. Fraternal twins are also called dizygotic twins. (12 Dec 1998) |
| acceptor site | The ribosomal binding site for the aminoacyl-tRNA during protein synthesis. (05 Mar 2000) |
| acceptor splicing site | Boundary between the right end of an intron and the left end of the adjacent exon. Synonym: acceptor splicing site. (05 Mar 2000) |
| active site | <chemistry> A specific region of an enzyme where a substrate binds and catalysis takes place (binding site). (06 May 1997) |
| allosteric site | A specific site on a multi-subunit enzyme or other protein that is not the substrate binding site, but that when reversibly bound by an effector, induces a conformational change in the protein, altering its catalytic or binding properties. (12 Dec 1998) |
| amidation site | <molecular biology> A C terminus consensus sequence, required for C terminus amidation of peptides. Consensus is glycine, followed by 2 basic amino acids (arg or lys). (18 Nov 1997) |
| antibody combining site | <immunology> In immune network theory, an idiotope, an antigenic site of an antibody that is responsible for that antibody binding to an antigenic determinant (epitope). Also used of the site on a ligand molecule to which a cell surface receptor binds. (18 Nov 1997) |
| antigen-binding site | <immunology> In immune network theory, an idiotope, an antigenic site of an antibody that is responsible for that antibody binding to an antigenic determinant (epitope). Also used of the site on a ligand molecule to which a cell surface receptor binds. (18 Nov 1997) |
| antigen-combining site | See: paratope. (05 Mar 2000) |