18) Which of the following describes enhancers?
| | They may contain binding sites for both activators andrepressors |
| | They regulate gene expression in prokaryotes |
| | They can only be located upstream of the coding sequence of aregulated gene. |
| | they only work if an insulator is located between the enhancerand its regulated gene |
| | all of the above |
20)
A single-base change occurs in the 5' splice site of a gene,resulting in a loss-of-function mutation. Scientists have found asuppressor mutation: a mutation in a second gene that counteractsthe first mutation. Which of the following is most likely tosuppress the original loss-of-function phenotype?
| | A mutation in the 3' splice site |
| | A mutation in the intron |
| | A mutation in an snRNP |
| | A mutation in a tRNA |
