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Chapter 28: Biomolecules: Nucleic Acids

Every problem in the chapter beside the book’s answer, a chapter at a time as you scroll.

Chapter 28: Biomolecules: Nucleic Acids

12 problems · 4 figures

28-1 §28.1 source ↗

Draw the full structure of the DNA dinucleotide AG.

Answer

28-2 §28.1 source ↗

Draw the full structure of the RNA dinucleotide UA.

Answer

28-3 §28.2 source ↗

What sequence of bases on one strand of DNA is complementary to the following sequence on another strand?

(5′) GGCTAATCCGT (3′)

Answer

(5′) ACGGATTAGCC (3′)

28-4 §28.4 source ↗

Show how uracil can form strong hydrogen bonds to adenine.

Answer

28-5 §28.4 source ↗

What RNA base sequence is complementary to the following DNA base sequence?

(5′) GATTACCGTA (3′)

Answer

(3′) CUAAUGGCAU (5′)

28-6 §28.4 source ↗

From what DNA base sequence was the following RNA sequence transcribed?

(5′) UUCGCAGAGU (3′)

Answer

(5′) ACTCTGCGAA (3′)

28-7 §28.5 source ↗

List codon sequences for the following amino acids:
(a)
Ala
(b)
Phe
(c)
Leu
(d)
Tyr

Answer (4 parts)

(a)
GCU, GCC, GCA, GCG
(b)
UUU, UUC
(c)
UUA, UUG, CUU, CUC, CUA, CUG
(d)
UAU, UAC

28-8 §28.5 source ↗

List anticodon sequences on the tRNAs carrying the following amino acids.
(a)
Ala
(b)
Phe
(c)
Leu
(d)
Tyr

Answer (4 parts)

(a)
AGC, GGC, UGC, CGC
(b)
AAA, GAA
(c)
UAA, CAA, GAA, GAG, UAG, CAG
(d)
AUA, GUA

28-9 §28.5 source ↗

What amino acid sequence is coded by the following mRNA base sequence?

CUU-AUG-GCU-UGG-CCC-UAA

Answer

Leu-Met-Ala-Trp-Pro-Stop

28-10 §28.5 source ↗

What is the base sequence in the original DNA strand on which the mRNA sequence in Problem 28-9 was made?

Answer

(5′) TTA-GGG-CCA-AGC-CAT-AAG (3′)

28-11 §28.7 source ↗

p-Dimethoxytrityl (DMT) ethers are easily cleaved by mild acid treatment. Show the mechanism of the cleavage reaction.

Answer

The cleavage is an SN1 reaction that occurs by protonation of the oxygen atom followed by loss of the stable triarylmethyl carbocation.

28-12 §28.7 source ↗

Propose a mechanism to account for cleavage of the β-cyanoethyl protecting group from the phosphate groups on treatment with aqueous ammonia. (Acrylonitrile, H2C ═ CHCN, is a by-product.) What kind of reaction is occurring?

Answer

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Problems and answers are adapted from Organic Chemistry: A Tenth Edition by John McMurry, OpenStax, and are used under the CC BY-NC-SA 4.0 licence. Access for free at https://openstax.org/books/organic-chemistry/pages/1-why-this-chapter. Illustrations: Copyright Rice University, OpenStax, under CC BY-NC-SA 4.0 license. This adaptation is released under the same licence, is non-commercial, and is neither affiliated with nor endorsed by OpenStax or Rice University.