NEW-klee-ar POOR A hole in the nuclear envelope. 70
Tiny openings that stud the nuclear envelope.
Periodic, highly organized, channels (patent holes) in the nuclear membrane across which macromolecules including mRNAs and transcription factors can be transported between the nucleus and the cytoplasm. They are evenly spaced throughout the membrane and are most easily seen by freeze fracture.
Nuclear pores are large protein complexes that cross the nuclear envelope, which is the double membrane surrounding the eukaryotic cell nucleus. There are about on average 2000 nuclear pore complexes in the nuclear envelope of a vertebrate cell, but it varies depending on the number of transcriptions of the cell. The proteins that make up the nuclear pore complex are known as nucleoporins.