About biological pt37(4)

ACD is selected. From the meaning of the title, the product of apoB gene expression in small intestinal cells is a protein with 50 amino acids, because there is a gene mutation, and the new codon produced by this mutation happens to be the stop codon, so 50 amino acids are missing when it is expressed. The gene can express protein of 100 amino acids in hepatocytes, indicating that the mRNA translated by protein has at least 303 bases (and a stop codon), so there are at least 60 genes. The mRNA length of genes transcribed by liver cells and small intestine cells is the same, but one of the codons has changed, so B is wrong. Because the front part of the gene has not changed, the first 50 amino acids expressed should be the same, and both proteins are the expression products of the gene, so the CD is correct; There is no splicing in gene transcription, so E is wrong.