Biology Now, 2e

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CHAPTER 10

END-OF-CHAPTER ANSWERS

1. gene expression: 2, gene regulation: 3, transcription: 1, trans-

lation: 4

2. (a) tRNA, (b) rRNA, (c) mRNA, (d) tRNA, (e) rRNA


3. redundancy, ambiguity


4. (See figure below)

Promoter

mRNA RNA polymerase

Gene Terminator

5. (a) 2, (b) 4, (c) 6, (d) 8, (e) 1, (f ) 9, (g) 5, (h) 3, (i) 7


6. a, b, c, d


7. (a) asparagine, (b) stop codon, (c) isoleucine, (d) glycine,

(e) pr ol i ne

8. (a) CGU, CGC, CGA, CGG, AGA, or AGG; (b) GCU, GCC,

GCA, or GCG; (c) AUG; (d) GGU, GGC, GGA, or GGG

9. b


10. e


11. At control point 2 (transcription), there might be an error in

up-regulation. At control point 3 (breakdown of mRNA) there

might be an error in down-regulation.

12. a


13. They are similar in that both involve building one molecule

from another. They differ in that gene expression is DNA to

RNA, while DNA replication is RNA to protein.

ANSWERS TO FIGURE QUESTIONS

Figure 10.3

Q1: Which is the faster way to produce vaccines: biopharming

with plants or creating vaccines in eggs? Why is this important?

A1: Biopharming in plants is faster, making it possible to bring

greater quantities of vaccine to the public to stem an outbreak

before it becomes an epidemic.

Q2: How much cheaper is biopharming with plants than creating

vaccines in eggs? Why is this important?

A2: Biopharming with plants is $364 million cheaper. The lower

cost means that the vaccines will be marketed to the public at

a much lower price. In addition, more insurance companies

will cover the lower costs, and more individuals will receive the

vaccine.

Q3: Why must tobacco-derived vaccines, or any new medications

for that matter, be approved by the FDA?

A3: The FDA is responsible for ensuring the safety of drugs (and

food). FDA approval is necessary because vaccines are drugs.

Figure 10.5

Q1: In which of the step(s) illustrated here does DNA replication

occur? In which step(s) does gene expression occur?

A1: Replication: steps 4 and 5. Expression: step 6.

Q2: Why do vaccine producers not simply replicate the entire viral

genome, instead isolating the gene for one protein and replicating

only that gene?

A2: Two reasons: It would take more time to replicate the entire

genome, and more important, the added time would allow the

vaccine to replicate and act like the infectious virus, causing

disease rather than preventing it.

Q3: What role do the bacteria play in this process? Why are they

needed?

A3: Because they can produce proteins much more quickly than

eukaryotes can, the bacteria rapidly generate the proteins needed

for the vaccine.

Figure 10.6

Q1: Why is only one strand of DNA used as a template?

A1: Because the other strand would code for the opposite mRNA.

Q2: If a mutation occurred within the promoter or terminator

region, do you think it would affect the mRNA transcribed? Why

or why not?

A2: Yes, because it wouldn’t be clear where the gene started or

stopped, so the mRNA might not be transcribed at all, or it would

grow too long.

Q3: The template strand of part of a gene has the base sequence

TGAGA AGACCAGGGTTGT. What is the sequence of RNA

transcribed from this DNA, assuming that RNA polymerase

travels from left to right on this strand?

A3: ACUCUUCUGGUCCCA ACA.

Figure 10.7

Q1: In your own words, define RNA splicing. When during gene

expression does it occur?

A1: RNA splicing removes the introns from the RNA transcript.

It occurs after transcription, but before the mRNA transcript is

translated into a protein.

Q2: What do you predict would happen if the introns were not

removed from RNA before translation? Why would it be a problem

if the introns were not removed?

A2: If the introns were not removed, they would be translated, and

the protein would be much larger and presumably nonfunctional.

Q3: Where is the mRNA destined to go once it has been

transported out of the nucleus?

A3: Into the cytoplasm.