recap

14.2 recap

The expression of protein-encoding genes can be broken down into two fundamental steps: transcription and translation. In transcription the DNA code is used to produce mRNA, whose sequence determines the mature mRNA transcript. The mRNA sequence determines the order of amino acids in a polypeptide. Translation is the process by which this information in mRNA is converted into a polypeptide chain.

learning outcomes

You should be able to:

  • Describe the central dogma of molecular biology.

  • Evaluate gene expression systems to determine whether they adhere to the central dogma of molecular biology.

Question 1

What is the central dogma of molecular biology?

The central dogma states that DNA is transcribed to RNA, which gets translated into protein, a process that is unidirectional.

Question 2

Do retroviruses violate the central dogma? Explain.

In retroviruses, the genome is RNA. To replicate, the RNA is converted to a DNA copy, which is then transcribed into RNA. This violated the original central dogma in that the DNA-to-RNA conversion was thought to be unidirectional.

We will revisit viral genetics in later chapters (in Key Concepts 16.3 and 25.4). In the rest of this chapter we will focus on gene expression in prokaryotes and eukaryotes. Understanding this process is essential for understanding how organisms function at the molecular level and is key to the application of biology to human welfare, in areas such as agriculture and medicine. We’ll begin by describing how the information in DNA is transcribed to produce RNA.