SQA National 5 Biology Practice Exam

The components that form the genetic code in DNA and mRNA are referred to as bases. DNA is composed of four types of nitrogenous bases: adenine, thymine, cytosine, and guanine. In RNA, thymine is replaced by uracil. These bases pair up (adenine with thymine or uracil, and cytosine with guanine) to form the structure of the DNA double helix and also determine the sequence of nucleotides in mRNA during transcription. This sequence of bases ultimately codes for the synthesis of proteins by dictating the order of amino acids. Understanding the role of bases in the genetic code is crucial for comprehending how genetic information is stored and expressed in living organisms.