Genetics: Analysis and Principles 5th Edition by Robert Brooker

Exercise 17

Describe the structure of a polysome, which is depicted in Figure 13.13a.FIGURE 13.13 Ribosomal structure. (a) Electron micrograph of ribosomes in the act of translation. Ribosomes are blue, mRNA is red, and polypeptides are green. (b) Crystal structure of the 50S and 30S subunits in bacteria. The rRNA is shown in gray strands (50S subunit) and turquoise strands (30S subunit), and proteins are shown in magenta (50S subunit) and navy blue (30S subunit). (c) A model depicting the sites where tRNA and mRNA bind to an intact ribosome. The mRNA lies on the surface of the 30S subunit. The E, P, and A sites are formed at the interface between the large and small subunits. The growing polypeptide exits through a hole in the 50S subunit.