You can't have a carrier with a dominant pedigree because other wise than individual or organism would be afflicted by the gene and render them incapable of being a carrier. A carrier is an individual/organism that has a normal phenotype (meaning it is not afflicted by said gene) but is carrying the gene that could cause disease or whatever the affect may be. In this case the gene would have to be homozygous recessive to be expressed. Hopefully this helps!
This is because the seven-sugar intermediate is synthesized by sugar addition to cytosolic-facing dolichol phosphate. The intermediate is flipped from the cytosol face of the ER membrane to the the luminal face. Additionally, the sugar additions then occur within the lumen of the ER. The short forms of the intermediate are on the wrong side of the membrane to add to nascent polypeptides within the ER lumen. Incomplete adductants within the ER lumen are located appropriately to N-glycosylate nascent polypeptide.
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