12.  Some point mutations are called silent mutations, i.e., the mutation does not change the amino acid after the altered mRNA is translated.  This is possible because the genetic code is
a.  universal                                                                   b.   degenerate
c.  both (a) and (b) are possible explanations     d.  neither (a) nor (b) are possible explanations

Examine the codon chart on page 231 of your text.  Note, for example, that both UUU and UUC are codons for phenylalanine.   The original DNA molecule that would specify such a codon would be AAA.  If a point mutation occurred in this region of the DNA so that it read AAG, then the resultant codon would be UUC.  However, the amino acid specified by the codon would not change; it would still read phenylalanine.

home13.gif (1441 bytes)BIOWEB  home13.gif (1441 bytes)Al BIO 101 Web Section  home13.gif (1441 bytes)ELI BIO 101 Web Section 
email.gif (404 bytes) nverdae@nvcc.edu
Emma Erdahl, Associate Professor of Biology
Northern Virginia Community College
Revised 8/23/00