Biology Now, 2e

A16 fiffAnswers

CHAPTER 9

END-OF-CHAPTER ANSWERS

1. c


2. d


3. a


4. d


5. nucleotide: 4, base pair: 1, DNA molecule: 3, base: 2


6. (See figure below)


7. PCR, CRISPR


8. c


9. (a) 1, (b) 5, (c) 3, (d) 2, (e) 4


10. (a) D, (b) S, (c) I


11. ATGCA A ATCCTGG

TACGTTTAGGACC

12. (a) 20% T, (b) 30% G, (c) 30% C


13. It is not possible to delete the PERV sequences in each cell of

the adult pig. Deleting the PERVs in the DNA of pig embryos

ensures that none of the resulting cells will contain PERV

sequences.

14. Yes, it matters. Noncoding DNA sequences still perform impor-

tant functions and can easily be disrupted by mutations. Regula-

tory regions rely on specific nucleotide sequences, and they could

become nonfunctional if those sequences are changed.

C A

G T

G T

C A

C

G

A

T

G

C

T

A

C

G

A

T

G

C

T

A

C

G

A

T

G

C

T

A

C

G

A

T

G

C

T

C A G T

A

G T C A

Template strand Newly synthesized strand

Separating strands

Base

Nucleotide

Base

pairs

ANSWERS TO FIGURE QUESTIONS

Figure 9.2

Q1: Name one reason why, for a potential transplant, matching the

size of organs shown would be important.

A1: The pig organs must fit into the space where the human organ

was removed. Organs that are too big will not fit. Organs that are

too small will not function at the level necessary to sustain life.

Q2: Name a tissue transplant for which size matching would not

be as important.

A2: Tissue from the cornea of the eye need not be exactly the same

size.

Q3: Name a tissue transplant for which size matching would not

be important at all.

A3: Bone marrow will replenish in any organisms regardless of

size matching.

Figure 9.3

Q1: Name two base pairs.

A1: Adenine-thymine (A-T) and cytosine-guanine (C-G).

Q2: Why is the DNA structure referred to as a “ladder”? What

part of the DNA represents the rungs of the ladder? What part

represents the sides?

A2: The structure looks like a ladder. The rungs are hydrogen

bonds, and the sides are the bases.

Q3: Is the hydrogen bond that holds the base pairs together a

strong or weak chemical bond? (Hint: Refer to Chapter 3 to review

chemical bonds, if necessary.)

A3: Wea k.

Figure 9.5

Q1: If all genes are composed of just four nucleotides, how can

different genes carry different types of information?

A1: Each gene is composed of different numbers of nucleotides in

different arrangements, thus allowing for many different types of

information to be conveyed.

Q2: Would you expect to see more variation in the sequence of

DNA bases between two members of the same species (such as

humans) or between two individuals of different species (for

example, humans and chickens)? Explain your reasoning.

A2: More variation would be expected between two individuals of

different species. Within a species, individuals have the same genes

but different alleles; across species, there are different genes and

different alleles.

Q3: Do different alleles of a gene have the same DNA sequence or

different DNA sequences?

A3: Different.