However - complementary GC-rich sequence and prevent...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
However, under low levels of tryptophan premature termination is inhibited because the stem loop cannot form from this inverted repeat ----- there is another GC-rich sequence complementary to the first repeat in front of the termination signal (sequence 2 in Figure). This sequence takes part in forming an alternative stem loop , which does not lead to premature termination because it is not followed by a strech of adenines. Why does this alternative stem loop not form normally? Because if translation occurs with normal speed, the ribosome will already cover the alternative
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: complementary GC-rich sequence and prevent alternative stem loop formation. Under low tryptophan levels translation is slowed at an earlier sequence of the mRNA (sequence 1 in Figure) simply because it contains codons for tryptophan, and tryptophan is scarce for translation. So the level of tryptophan directly determines the speed of translation , which in turn determines the kind of stem loop that is formed , either the one that can prematurely terminate transcription (high tryptophan levels) or the one that cannot (low tryptophan levels)....
View Full Document

{[ snackBarMessage ]}

Ask a homework question - tutors are online