DNA Replication 1
Considering the structure of double stranded DNA, what kind of bonds hold one complementary strand to the other?
hydrogen bonds
Which enzymes remove supercoiling in replicating DNA ahead of the replication fork?
topoisomerase
Why is an RNA primer necessary for DNA replication?
A. The RNA primer provides the free 3′ end required by DNA pol I
B. The RNA primer is required for the proper activity of DNA ligase
C. DNA polymerase can only add nucleotides to RNA molecules
D. DNA polymerase can only add nucleotides to an existing strand
D. DNA polymerase can only add nucleotides to an existing strand
Which component is not directly involved in translation?
A. mRNA, which provides the codon sequence for protein synthesis
B. DNA, which serves as the genetic template stored in the nucleus
C. tRNA, which delivers specific amino acids during protein synthesis
D. ribosomes, which facilitate the assembly of the polypeptide chain
E. amino acids, which serve as the building blocks of the protein
B. DNA, which serves as the genetic template stored in the nucleus
What two molecules form the sides or backbone of the DNA ladder?
deoxyribose sugar and phosphate
Which enzymes are involved in the unwinding and connecting DNA strands?
helicase and ligase
Which enzyme adds RNA nucleotides to mark the starting point for the synthesis of new DNA strand?
primase
What do you call the expressed and non-expressed areas of the mRNA, respectively?
exon and intron
A section of DNA has the following sequence of nitrogenous bases: CGATTACAG. What would be produced as a result of transcription?
GCUAAUGUC
Which defines a codon?
A. a protein that separates DNA strands by breaking hydrogen bonds
B. a nitrogenous base that attaches to exposed DNA during strand synthesis
C. a sequence of three bases on mRNA that specifies a single amino acid
D. a type of bond that holds complementary nitrogen bases together in DNA
C. a sequence of three bases on mRNA that specifies a single amino acid
If the activity of DNA ligase was removed from replication, this would have a greater effect on ______?
A. joining of DNA fragments on the leading strand compared with the lagging strand
B. joining of DNA fragments on the lagging strand compared with the leading strand
C. initiation of DNA synthesis by RNA primers compared with elongation of DNA strands
D. repair of DNA damage by excision mechanisms compared with joining of DNA fragments
B. joining of DNA fragments on the lagging strand compared with the leading strand
The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?
A. nuclease, DNA polymerase, DNA ligase
B. telomerase, primase, DNA polymerase
C. telomerase, helicase, single-strand binding protein
D. DNA ligase, RNA polymerase, nuclease
A. nuclease, DNA polymerase, DNA ligase
What is added to the 3'-end of many eukaryotic mRNAs after transcription?
poly A-tail
Which of the following sets of codons activates release factors to terminate translation?
A. AUG, UAG, UGA
B. UAG, UAC, UGG
C. UAA, UAG, UAC
D. UGA, UAG, UAA
D. UGA, UAG, UAA
The DNA coding strand has the sequence 5′– ATCAGCGCTGGC –3′. If the DNA template strand is read in the 3′ → 5′ direction, what are the first and last amino acids coded by this sequence?
First amino acid: Isoleucine
Last amino acid: Glycine
Suppose a mutation occurs in a cell such that normal Okazaki fragments are formed during DNA replication, but the RNA primers are not replaced with DNA. Which enzyme is most likely affected by this mutation?
DNA polymerase I
Which of the following best explains why DNA synthesis on one strand is discontinuous during replication?
A. DNA polymerase requires a free 3′ end to begin synthesis of a new strand
B. DNA polymerase reads the template strand only in the 3′ → 5′ direction
C. DNA polymerase must repeatedly stop to add additional nucleotides
D. DNA polymerase synthesizes new DNA strand only in the 5′ → 3′ direction
D. DNA polymerase synthesizes new DNA strand only in the 5′ → 3′ direction
If the sequence of DNA on the template strand of a gene is AAA, the mRNA codon produced by transcription will be _______ and will specify the amino acid _______ .
UUU, phenylalanine
Using an mRNA codon chart, identify the 3′ → 5′ DNA template strand sequence that would produce an mRNA coding for the polypeptide Serine – Proline – Lysine.
A. 3′– TCT – GGT – TTT –5′
B. 3′– AGT – GGG – AAA –5′
C. 3′– AGA – GGT – TTT –5′
D. 3′– TCA – CCA – AAG –5′
C. 3′– AGA – GGT – TTT –5′
Which of the following processes occurs during post-translational modification of proteins?
A. Synthesis of RNA from DNA by RNA polymerase
B. Removal of exons and joining of introns in pre-mRNA
C. Addition of a 5′ cap and a 3′ poly-A tail to mRNA
D. Folding and chemical modification of a polypeptide
D. Folding and chemical modification of a polypeptide
A chemical inhibits telomerase activity in a dividing cell. Which of the following would MOST likely be observed?
A. Chromosome ends would progressively shorten after repeated DNA replication cycles
B. Chromosome ends would fail to replicate after repeated DNA replication cycles
C. Chromosome ends would progressively lengthen after repeated DNA replication cycles
D. Chromosome ends would fail to separate properly after repeated DNA replication cycles
A. Chromosome ends would progressively shorten after repeated DNA replication cycles
During bidirectional DNA replication from a single origin, two replication forks move in opposite directions. If the upper (top) parental strand runs in the 5′ → 3′ direction from left to right, which of the following correctly describes DNA synthesis at both replication forks?
A. At the left fork, the upper strand is lagging and the lower strand is leading, while at the right fork, the upper strand is leading and the lower strand is lagging
B. At the left fork, the upper strand is leading and the lower strand is lagging, while at the right fork, the upper strand is leading and the lower strand is lagging
C. At the left fork, the upper strand is lagging and the lower strand is leading, while at the right fork, the upper strand is lagging and the lower strand is leading
D. At the left fork, the upper strand is leading and the lower strand is lagging, while at the right fork, the upper strand is lagging and the lower strand is leading
D. At the left fork, the upper strand is leading and the lower strand is lagging, while at the right fork, the upper strand is lagging and the lower strand is leading
Suppose you mix the following components of protein synthesis in a test tube: amino acids from a rabbit, ribosomes from a dog, tRNAs from a mouse, mRNA from a chimpanzee, and necessary enzymes plus an energy source from a giraffe. If protein synthesis occurs, which animal’s protein will be made?
chimpanzee
A protein is synthesized using a DNA template strand that is read in the 3′ → 5′ direction. What are the amino acid sequences produced from the following DNA coding strand?
5′– ATG TCG ACA GCC GGA TTT TAA –3′
Met – Ser – Thr – Ala – Gly – Phe – Stop
A defect occurs in single-strand binding proteins during the initiation stage. Which of the following would MOST likely be observed?
A. DNA strands would fail to unwind at the replication fork region
B. DNA fragments would fail to join at the replication fork region
C. DNA strands would rejoin after unwinding at the replication fork region
D. RNA primers would fail to extend at the replication fork region
C. DNA strands would rejoin after unwinding at the replication fork region