Transcription

Study Problems.

1. There are several terms that you should add to your vocabulary. These are listed on pp. 842-843 of Voet & Voet. Make sure you do not miss any.

2. Work "Study Exercises" 1-7 at the end of Chapter 25 in Voet & Voet.

3. Work "Problems" 1,3, and 5 at the end of Chapter 25 before you look up the answers at the end of the book.

4. The sigma subunit of E. coli RNA polymerase

A. is part of the core enzyme.

B. binds the antibiotic rifampicin. It is the b subunit that binds rifampicin.

C. is inhibited by a -amanitin This toxin from certain mushrooms inhibits eukaryotic RNA polymerase II

D. must be present for transcription to occur. s is only required for initiation.

E. allows the enzyme to recognize promoter sites.

ANSWER: E

5. Mark which statements are "True" and which are "False" about the primary transcript in prokaryotes.

A. It contains a triphosphate group at its 5' end.

B. It contains an AU-rich sequence complementary to the -10 region of the DNA template. This part of the DNA is not transcribed.

C. It sometimes contains information for more than one protein. For example, polycistronic mRNA

D. It sometimes contains a hairpin structure near its 3'-end. Some mRNAs are terminated distally to such hairpin structures.

E. It usually contains a poly A sequence near its 3'-end. No; however, polyA has been detected in many prokaryotic mRNAs and its possible physiological significance is currently under evaluation.

ANSWER: A, C and D are true; B and E are false, except as noted.

6. Use the statements in question 5 to mark those that are false about the primary transcript in eukaryotes.

ANSWERS: A = True; B= False; C= False (few exceptions); D= False (usually); E= True