A chalazion is caused by the oil in the gland becoming too thick to flow out of the gland or the opening of the gland being obstructed. Without anywhere to go, the oil builds up inside the gland and forms a lump in the eyelid.ach of the oil glands, called meibomian glands, produces oil that flows out of the gland into the tears. The oil exits from each gland through a tiny circular opening just behind the eyelashes of the upper and lower lids of both eyes.
Transcription activator-like effector nucleases (TALENs) are artificial restriction enzymes generated by fusing a TAL effector DNA-binding domain to a DNA cleavage domain.Restriction enzymes are enzymes that cut DNA strands at a specific sequence.rom Wikipedia, the free encyclopedia. Transcription activator-like effector nucleases (TALENs) are artificial restriction enzymes generated by fusing a TAL effector DNA-binding domain to a DNA cleavage domain. Restriction enzymes are enzymes that cut DNA strands at a specific sequence.
A transcription unit is a linear sequence of DNA that extends from a transcription start site to a transcription stop site (Figure 4). Figure 4. The promoter, a DNA sequence that lies upstream of the RNA coding region, serves as an indicator of where and in which direction transcription should proceed.The promoter is not actually transcribed; its role is purely regulatory.he terminator, a sequence of nucleotides at the end of the transcription unit, is transcribed along with the RNA coding region. The terminator serves as a speed bump of sorts; transcription stops only after this region has been transcribed.