NAME______Key_______________________

Please write clearly. No credit will be given for illegible answers.

1. Which of the following is more likely to be involved in the regulation of a gene whose product needs to be produced very quickly in response to environmental change (circle one)?

3. How does heterochromatin differ structurally and functionally from euchromatin?

Heterochromatin is tightly packed and the DNA is physically unavailable for transcription. Euchromatin is loosely packed and is available for transcription

4. Give one specific piece of evidence that hormones control development.

Any experiment (e.g. frog or Rhodnius) in which hormone injection at the wrong time or removal of the source of a hormone changes the pattern of development

5. What is the role of the signal molecule tryp in negative repression of the tryp operon (i.e. what molecule(s) does it interact with and what effect does this have on the operon)?

Tryp (a co-repressor) binds to the regulatory protein making it active. The active repressor turns the operon off.

6. Why does the blood sucking bug Rhodnius metamorphose into an adult only after its 4th molt?

Juvenile hormone, which inhibits the action of ecdysone, is only produced up to the fourth molt. In the absence of juvenile hormone, ecdysone triggers metamporphosis.