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Discussion Guide Chapter 12
Mader, 10th Edition
First three questions are review.
1. Each unit of a nucleic acid consisting of a sugar, attached phosphate group and a base is a
____________________
2. In a nucleic acid, the bases are always attached to the ________ carbon of the sugar. The free
hydroxyl group is attached to the_______ carbon of the sugar. The phosphate group is attached
to the ______ carbon of the sugar.
3. List the pyrimidines and purines for DNA. Describe the shape of a DNA molecule if purines
paired with purines and pyrimidines paired with pyrimidines.
4. Amazingly, an alien species of cellular organization is found alive in the remains of a meterorite
that landed in the Mojave Desert. As a scientist, you are trying to determine whether this alien
life form uses DNA, protein or some other type of compound as its hereditary material.
a. What kinds of experiments would you propose to determine what the hereditary material
is?
5. Using Chargaff’s rules, write the base sequence of the complementary strand below the DNA
strands below
a. CATGGTA
b. TTGGCAA
c. AGCTACG
6. Differentiate between the three main replication enzymes. (see Science Focus p. 218)
Helicase
DNA Polymerase
DNA Ligase
7. A new form of DNA is discovered that appears to be able to replicate itself both in the 3’ → 5’
direction and in the 5’ → 3’ direction. If this is true, how would this newly discovered DNA
replication differ from DNA replication as we know it?
8. What are the three ways transcription differs from DNA replication?
9. mRNA molecules are not used exactly as transcribed in eukaryotic cells. Compare each of the
following processes:
a. 5’ caps vs. 3’ poly-A tails
b. Intron vs. exon
10. ___________________ ______________ is where one gene can specify two or more proteins
that differ in ____________ and _________________.
11. Refer to figure 14.6. To the right of each triplet listed below, list the associated amino acid. If
none, list the effect of the triplet.
a. codon UUG
f. codon AUG
b. codon CCG
g. DNA triplet AAA
c. codon GGA
h. codon UAG
d. anticodon GCC
i. codon UGG
e. codon GUC
j. anticodon UCA
12. Several different types of RNA exist in prokaryotic and eukaryotic cells. List the three main
types of RNA involved in transcription and translation. Answer the following questions to
complete the chart.
a. Types of RNA
b. Where are they
c. Where and how do they
produced?
function in cells?
13. What is an anticodon? Where is it found?
14. Why are there less than 64 tRNAs?
15. Give a brief description of the events of the three stages of translation.
Initiation
Elongation
Termination
16. Given your understanding of transcription and translation, fill in the blanks below and indicate
the 5’ and 3’ ends of each nucleotide sequence. Assume no RNA processing occurs.
Nontemplate strand of DNA
Template strand of DNA
mRNA
Anticodons on complementary
tRNA
5’ A T G T A T G C C A A T G C A 3’
_’ T _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _’
_’ A _ _ _ _ U _ _ _ _ _ _ _ _ _ _ _’
_’ _ _ _/_ _ _/_ _ _/_ _ _ /_ _ _/_’