Apo B48 & Apo B100 is synthesized from the same mRNA; the difference between them is due to:
**Core Concept**
Apo B48 and Apo B100 are two forms of apolipoprotein B (Apo B), a key protein component of low-density lipoproteins (LDL) and chylomicrons. They are synthesized from the same mRNA precursor but undergo different post-translational processing steps to produce distinct proteins.
**Why the Correct Answer is Right**
The difference between Apo B48 and Apo B100 is primarily due to the presence or absence of a 48-amino acid peptide, which is removed from the Apo B100 precursor. This removal occurs through a process called endoproteolytic cleavage, mediated by the enzyme apolipoprotein B mRNA editing enzyme, catalytic polypeptide 1 (APOBEC-1). APOBEC-1 specifically targets the Apo B100 mRNA, leading to the removal of the 48-amino acid peptide and the production of Apo B48. In contrast, Apo B100 is produced when this editing process is incomplete or absent.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect - This option does not specify the mechanism of Apo B48 and Apo B100 synthesis, which is the key to understanding their difference.
**Option B:** Incorrect - This option is incomplete and does not accurately describe the post-translational processing steps involved in Apo B48 and Apo B100 synthesis.
**Clinical Pearl / High-Yield Fact**
Apolipoprotein B mRNA editing is a crucial process that regulates the production of Apo B48 and Apo B100. This editing process is also involved in the pathogenesis of certain diseases, such as atherosclerosis and hypertriglyceridemia.
**Correct Answer:** C.