21. The enzyme that can proofreads replicating DNA, detects incorrect bases, excises them, and correctly replaces them is 
A. DNA ligase
B. DNA polymerase
C. DNA helicase
D. DNA gyrase
E. Primase

22.  The site where the old DNA strands separate and new DNA strands will be synthesized is called the  
A.  Primer
B.  Okazaki fragment
C.  Template
D.  Rolling circle
E.  Replication fork

23.  DNA gyrase  
A.  Unwinds DNA
B.  Supercoils DNA
C.  Cleaves DNA
D.  Joins free DNA ends
E.  None of the choices are correct

24.  Helicase  
A.  Unwinds DNA
B.  Supercoils DNA
C.  Unwinds RNA
D.  Winds RNA
E.  None of the choices are correct

25.  DNA Polymerase I  
A.  Removes primers
B.  Adds bases to new DNA chain
C.  Seals DNA gaps
D.  Proofreads DNA chain
E.  All of the choices are correct

26.  DNA Polymerase III  
A.  Synthesizes primer
B.  Removes primer
C.  Joins Okazaki fragments
D.  Unzips the DNA helix
E.  Proofreads new DNA

27.  A permanent, inheritable change in the genetic information is called a(n)  
A.  Translation
B.  Transcription
C.  Mutation
D.  Alteration
E.  Regeneration

28.  Replication of DNA begins at a(n)  
A.  Guanine-cytosine rich area
B.  Uracil-adenine rich area
C.  Adenine-thymine rich area
D.  Adenine-cytosine rich area
E.  Guanine-adenine rich area

29. A primer of ____ is needed at the origin of nucleotide addition. 
A. Polymerase III
B. Polymerase I
C. Helicase
D. RNA
E. DNA

30.  Groups of three consecutive bases along the DNA of a gene have the code for one  
A.  Protein
B.  Nucleotide
C.  Amino acid
D.  Purine
E.  None of the choices are correct