DNA Replication
After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand?
A) ligase, primase, DNA polymerase, helicase
B) primase, helicase, DNA polymerase, ligase
C) helicase, DNA polymerase, primase, ligase
D) helicase, primase, DNA polymerase, ligase
E) helicase, primase, ligase, DNA polymerase
D) helicase, primase, DNA polymerase, ligase
Which statement correctly describes mRNA processing?
a) Introns are cut out of the primary transcript, and the resulting exons are spliced together.
b) Exons are cut out of the primary transcript, and the introns are spliced together.
c) Exons are cut out of the primary transcript and transported to the endoplasmic reticulum.
d) Introns are cut out of the primary transcript and spliced together at the end of the transcript.
a) Introns are cut out of the primary transcript, and the resulting exons are spliced together.
In prokaryotic genomes, groups of functionally related genes along with their promoters and operators are found together in __________.
a) an operon
b) a regulatory gene
c) a repressor
d) an enhancer
e) a transcription factor
a) an operon
Muscle cells different from nerve cells mainly because they
A) Express different genes
B) Contain different genes
C) Use different genetic codes
D) Have unique ribosomes
A) Express different genes
The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called __________.
a) helicase
b) ligase
c) primase
d) topoisomerase
d) topoisomerase
Which of the following statements is true?
A) It takes three genes to code for one protein
B) Each amino acid in a protein is coded for by three bases in the DNA
C) Each gene codes for three proteins
D) Each triplet has many different meanings.
E) Each DNA base codes for three amino acids.
B) Each amino acid in a protein is coded for by three bases in the DNA
Gene expression in bacteria is regulated primarily by __________.
a) controlling the translation of mRNA to produce polypeptides
b) transcription factors encoded for by mitochondrial DNA
c) controlling gene packing and unpacking
d) selectively breaking down the proteins encoded by the genes
e) controlling the transcription of genes into mRNA
e) controlling the transcription of genes into mRNA
The incorporation of an incorrect base into the DNA during replication __________.
a) will trigger the cell to destroy the new strand, and replication will begin again
b) is virtually impossible, as the accuracy of DNA polymerase is such that errors almost never occur
c) can be repaired by the mismatch repair system
d) cannot be repaired, and a new mutation will invariably result
e) will almost certainly lead to the death of the cell
c) can be repaired by the mismatch repair system
DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments).
A) 3′ end ... 5′ end
B) sugar group ... phosphate group
C) 3′ end ... 3′ end
D) 5′ end ... 3′ end
E) 5′ end ... 5′ end
C) 3′ end ... 3′ end
Which summary of protein synthesis is correct?
A) DNA exchanges its thymine units with uracil in polymerase. This activates polymerase, and it starts joining amino acids together.
B) Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to the mRNA through codon-anticodon pairing.
C) Replicated DNA leaves the nucleus, is transported to a ribosome, and catalyzes the polymerization of amino acids in a protein.
D) Transfer RNAs line up on a ribosome, and amino acids bind to them with hydrogen bonds.
B) Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to the mRNA through codon-anticodon pairing.
Which type of mutation is least likely to affect protein function?
a) insertion of three bases
b) base-pair substitution
c) addition of single bases
d) deletion of single bases
b) base-pair substitution
Which is a post-translational modification of a polypeptide?
a) removal of introns and splicing of exons
b) The growing polypeptide signals the ribosome to attach to the ER.
c) formation of a polysome that allows simultaneous formation of many polypeptides from one mRNA transcript
d) cleavage of a polypeptide into two or more chains
d) cleavage of a polypeptide into two or more chains
Explain what the semi-conservative model of DNA replication is (what is its end result?).
After one round of replication, each of the two daughter molecules is composed of one old and one new strand.
How many nucleotides are needed to code for a protein with 450 amino acids?
A) at least 150
B) at least 900
C) at least 1,350
C) at least 1,350
In general, operons that encode the enzymes of a biosynthetic (anabolic) pathway (such as the trp operon) are __________, and those encoding the enzymes of a catabolic pathway (such as the lac operon) are __________.
a) permanently off ... permanently on
b) inducible ... repressible
c) easily mutated ... resistant to mutations
d) repressible ... inducible
e) permanently on ... permanently off
d) repressible ... inducible
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
a) irreversible binding of the repressor to the promoter
B) reduced transcription of the operon's genes
C) buildup of a substrate for the pathway controlled by the operon
D) Continuous transcription of the operon's genes
D) Continuous transcription of the operon's genes