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Chapter 12 Introduction

Biological Sciences
Course Code
Mark Fitzpatrick

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Chapter 12: Central Dogma, Transcription & the genetic Code
Question 1: Which of the following repair mechanism is most likely to be used in a cell that in
not dividing?
a. Proofreading b. Mismatch repairc. Excision repair
Answer: c
In excision repair, damaged nucleotides due to mutagen (ultraviolet radiation, X-ray) are
recognized. Wrong nucleotides are excised and complementary nucleotide paired with the
strand. This process happens in all cells, not just in DNA replication
Proofreading & mismatch repair only occurs in DNA replication. Proofreading takes place
before & mismatch repair takes place after DNA replication.
Question 2: Of the proteins listed, which of these proteins binds to DNA earliest during DNA
a. Single stranded binding proteinb. Ligase c. DNA polymerase III
d. DNA polymerase I e. Telomerase
Answer: a
After helicase unzips the DNA strands, single stranded binding protein binds to each DNA
strand, preventing them from annealing.
The chronological order of enzyme in DNA replication is a. single stranded binding protein, c.
DNA polymerase III, e. DNA polymerase I, b. ligase, then e. telomerase.
Question 3: If a strand of DNA is analyzed and contains 20 percent A bases, what percent of the
strand contains G bases?
a. 20 b. 30 c. 40 d. 60 e. 80
Answer: b
According to the complementary base theory, percentage of A equals T, and percentage of C
equals G.
Percentage of G = (100% - % of A - % of T) /2 =30
Question 4: Which of the following statements about the replication of DNA is false?
Answer: a
In DNA replication, nucleotides are added to both strands only in 5’ to 3’ direction.
Application of DNA Structure & Replication
-DNA sequencing determine a particular base sequence of DNA
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