The predominant cells in blood are the red blood cells (RBC) which contains a protein called hemoglobin. Hemoglobin is the principal determinant of the color of blood. Arterial blood and capillary blood are bright red, as oxygen imparts a strong red color to the heme group.
Concept 21 RNA is an intermediary between DNA and protein. DNA is found mostly in the cell nucleus, but another type of nucleic acid, RNA, is common in the cytoplasm. Watson and Crick proposed that RNA must copy the DNA message in the nucleus and carry it out to the cytoplasm, where proteins are synthesized. Crick also predicted the existence of an adaptor molecule that reads the genetic code and selects the appropriate amino acids to add to a growing polypeptide chain.
Second, there are four different nitrogenous bases found in DNA and RNA; however, there is one difference. The bases found in DNA are guanine, cytosine, adenine, and thymine. The bases found in RNA are guanine, cytosine, adenine, and uracil. Uracil forms two hydrogen bonds with adenine and functions just like thymine does. It's simply used in RNA instead of thymine.