Download Biology 102, Lectures 17 and 18 Study Guide

Biology 102, Lectures 17 and 18 Study Guide
February 23 & 25, 2004
TOPIC: Gene Expression and Regulation
Outline (both lectures); For a more detailed outline and details, see PowerPoint slides and your
own lecture notes.
Remember, study the course material, and then test yourself with the study questions! Don’t try
to just learn the answers to the study questions or you will have a somewhat disjointed view of
the topics.
I.
II.
III.
IV.
V.
The relationship of genes and proteins
A. Review: Role of proteins
B. Beadle and Tatum experiment
C. One gene: one protein
From Gene to Protein
A. RNA
B. Overview: From gene to protein
C. The genetic code
Transcription (details)
A. Steps
B. Further modification of mRNA
Translation
A. NOTE: In the PowerPoint presentation, the words on “Translation: Elongation 2”
should be on the slide titled “Translation: Elongation 3”, and visa versa
B. Review of what translation is
C. Types of RNA and their functions
D. Overview of translation
E. Details of translation
Information flow through cell
Study questions
1. List several roles of protein in cells. Try to think of as many as you can!
2.
For the Beadle and Tatum experiments:
a. What type of organism is Neurospora (the organism they studied)?
b. What sort of mutations did they induce in the Neurospora (i.e. what was “wrong” with
the mutants)?
c. Explain why Mutant A could only grow on arginine, whereas Mutant B can grow on
either citruline or arginine.
d. What was the key conclusion that Beadle and Tatum arrived at with these experiments
(so important that they won the Nobel Prize for developing this concept)?
3.
In one sentence or phrase, state what is accomplished:
a. during the process of transcription?
b. during the process of translation?
4.
What are the structural differences between RNA and DNA?
5.
List the 3 different types of RNA and describe the function of each type during the processes
of transcription and translation.
6.
What is a codon? Which type of molecule has codons? How are codons related to the
genetic code?
7.
Where in the cell does transcription occur?
8.
List the three major steps of transcription, and describes what happens during each as
precisely as possible.
9.
What is the function of the promoter region of gene?
10. During the process of transcription, does the DNA molecule unwind completely?
11. What are the functions of RNA polymerase during transcription?
12. Once synthesized, how is mRNA further modified prior to leaving the nucleus? What are
the functions of this modification (one known, one more speculative)?
13. What is an anticodon? Where are anticodons found? How do they function during the
process of translation?
14. What are the three major steps of the translation process?
15. During the first step of translation (initiation), what happens? (Three major steps)
16. During the elongation phase of translation:
a. Where along the mRNA molecule does translation begin? (At the beginning? At a
starting point determined by a particular base sequence, perhaps?)
b. What do the tRNA molecules carry?
c. What determines which tRNA molecule will enter the open site on the ribosome?
d. What is the function of the catalytic site (what reaction is catalyzed)?
e. Be able to describe the events that occur during elongation in order
f. NOTE: In the PowerPoint presentation, the words on “Translation: Elongation 2”
should be on the slide titled “Translation: Elongation 3”, and visa versa. The images
are in the correct order.
17. What is the “signal” for translation to stop?
18. What happens to the ribosome after all associated molecules detach?
19. Given the following sequence of DNA (template strand) at the beginning of gene to be
translated
TTTACTGATTAACT
a.
b.
Indicate the corresponding sequence of mRNA (assume this is a portion of an exon, not
an intron)
Translate the sequence into its appropriate amino acid chain (HINT: Be sure you start
your translation in the right place!)
20. What amino acid is carried by the tRNA with the anticodon UGA?
21. While I’ve tried to drum into you that a gene codes for a protein, what else do genes code
for?
NOTE: Answers to 19-20 are here. Try them first to make sure you get the same answer. If
you’ve missed them, be sure you understand why!
19a. mRNA: AAAUGACUAAUUGA
19b. amino acid sequence: Remember you have to find the “start” codon!
Methionine-threonine-asparagine-stop
20. The anticodon UGA (on the tRNA) corresponds with the codon ACU (on the mRNA),
which translates to the amino acid threonine. If you said it was the “stop” codon you did not
remember that the genetic code chart shows you the mRNA!
21. Be sure you understand the diagram “Overview of Information Flow in the Cell”.
Essentially, this diagram gives you the pathway of protein synthesis and breakdown in the
cell. [A bit more of this in the next outline.]