[单项选择] The Central Dogma Though it comes as no surprise that the composition of DNA between different organisms is different, it is not immediately obvious why the muscle cells, blood cells, and brain cells of any one particular vertebrate(脊椎动物) are so different in their structure and composition when the DNA of every one of their cells is identical. This is the key to one of the most exciting areas of modern cell biology. In different cell types, different sets of the total number of genes (genome) (基因组) are expressed. In other words, different regions of the DNA are "active" in the muscle cells, blood cells, and brain cells. To understand how this difference in DNA activity can lead to differences in cell structure and composition, it is necessary to consider what is often known as the central dogma(法则) of molecular biology: "DNA makes RNA make protein. " In molecular terms, a gene is that portion of DNA that encodes for a single protein. The dictum" o
A. the proteins that are released from the ribosome fold into unique shapes because of their particular sequence
B. the structure of the emerging molecule is determined by the protein primary sequence
C. several million copies of proteins carry out several million kinds of functions
D. the sequence of gene is translated into an amino acid chain