When a membrane protein is radioactively labeled during synthesis and followed through the various organelles in the secretory pathway, all the radioactivity is concentrated in the cis-Golgi apparatus six hours after the protein synthesis. This suggests that the protein a. is misfolded and being degraded in the cis-Golgi.
b. contains a KDEL sequence near its C-terminus.
c. has a membrane-spanning domain length equals the
d. thickness of the cis-Golgi membrane.
e. was imported directly into the cis-Golgi posttranslationally.
f. has a mannose-6-phosphate tag.

C. has a membrane-spanning domain length equals the thickness of the cis-Golgi membrane.

Explanation:

Secretory pathway is the pathway that transport proteins to the cell surface membrane. For this, the membrane proteins are labeled radioactively and move through the various organelles to carry the proteins to the surface membrane.

After six hours, all the radioactivity is concentrated in the cis-Golgi apparatus this means that The protein carries membrane-spanning domain which widens or make the cis-Golgi menbrane thick.

Hence, the correct answer is "C".

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multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.