Biology 111B

Study Questions 15

TRANSCRIPTION AND TRANSLATION

1. What do the following terms mean?

transcription
translation
codon
mRNA
tRNA
rRNA
anticodon

2. What is RNA, and how is it different from DNA? What are the three kinds of RNA, and what is the purpose of each?

3. How does the mRNA copy differ from the DNA template from which it is made?

4. How is mRNA made from DNA? What enzyme catalyzes this reaction?

5. How does the enzyme know where to start and stop transcription?

6. How is a eukaryotic primary transcript different from finished mRNA? What about a prokaryotic primary transcript?

7. How is protein made from mRNA? What raw materials must be present for this process to occur? Why is it important for translation that ribosomes contain three sites for tRNA and not just one?

8. Why can transcription and translation be simultaneous in prokaryotes but not in eukaryotes?

9. What is the function of the 5' cap on an mRNA? What about the 3' poly A tail?

10. What is a polyribosome?

11. All of the following are directly involved in translation except ...

a. mRNA

b. tRNA

c. DNA

d. ribosomes

e. all of the above are involved

12. A protein contains 30 amino acids. How many N-bases code for this protein?

13. What tells the ribosome where to start translation and stop translation?

14. Which of the molecules in the list on the right function to transfer information in the processes on the left? (Write the correct answer(s) on the blank line.)

Information transfer...
_________ from nucleus to cytoplasm	a. proteins	e. rRNA
_________ from DNA to mRNA	b. tRNA	f. DNA polymerase
_________ from mRNA to protein	c. DNA	g. RNA polymerase
	d. mRNA	h. ligase

15. Refer to the double stranded DNA molecule with the sequence below to answer parts a - d.

a. Which strand functions as the transcription template, the top one or the bottom one? Explain your reasoning.

b. What is the mRNA transcript and polypeptide from this strand? In the space below, copy the DNA strand that is transcribed, and write the mRNA transcript and polypeptide chain below it. Align the mRNA and polypeptide so that it is clear which DNA bases they came from.

DNA strand:

mRNA:

amino acid sequence:

c. How would the amino acid sequence differ if

the DNA base pair 22 were changed from G/C to A/T?

the DNA base pair 12 were changed from C/G to T/A?

the DNA base pair 4 were changed from T/A to C/G?

d. How would the amino acid sequence differ if an extra A/T base pair were inserted between base pairs 8 and 9?