The enzyme that unwinds a segment of the DNA molecule is...
answer
Helicase.
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The enzyme that travels along the leading strand assembling new nucleotides on a growing new strand of DNA is...
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DNA Polymerase
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Before the lagging strand can begin assembling new DNA nucleotides, which of the following must occur?
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RNA primase constructs a short RNA primer.
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If DNA ligase was nonfunctional, what would be a likely consequence?
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DNA replication would occur, but the lagging strand would be non-functional.
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How do DNA polymerase I and DNA Polymerase III differ?
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DNA Polymerase III synthesizes the majority of the DNA, while DNA Polymerase I synthesizes DNA in the regions where the RNA primers were laid down on the lagging strand.
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Which characteristic of DNA allows each strand of the molecule to act as a template that specifies the exact sequence of nucleotides in the other strand?
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Complementarity of the bases.
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Arrange the following proteins in the proper order in which they participate in DNA replication.
1 = Primase
2 = Helicase
3 = Single-strand binding proteins
4 = DNA polymerase I
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2, 3, 1, 4.
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Which of the following is required to replicate the lagging strand of DNA?
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Okazaki fragments, primase and DNA ligase.
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RNA primers are removed by the action of the enzyme
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DNA pol I.
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DNA replication is said to be
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semi-conservative.
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Which of the following DNA sequences is complementary to 5' TAGAC 3'?
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5' GTCTA 3'
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According to Chargaff's rule, which of the following statements about double-stranded DNA is TRUE?
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A = T and C = G and A + G = C + T
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Evaluate the statements below and select the one that best explains why is the replication machinery found at the replication fork?
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The replication machinery must have access to the leading and laggings strands for replication, and it must be able to open and stabilize the template DNA.
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Based on your knowledge of the structure of DNA, why is it more likely for a G to mutate to an A than to a C or a T?
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Because the structure of both G and A are similar in that they have a double ring.
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DNA polymerases cannot replicate
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the 3' end of linear chromosomes.
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Telomerase is unique because it contains
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an RNA molecule.
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Which of the following best describes the function of telomerase at the telomere?
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It adds new DNA to the longer strand of the telomere overhang.
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What might be the consequence of an organism that was born without functional telomerase?
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The organism would have shorter chromosomes with every round of mitosis, which would eventually result in cancer or cells that were unable to properly function and it would die earlier than normal
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An organism has a mutation in its telomerase, so that the RNA template is 3' AAACCCCAAC 5' rather than the normal 3' AACCCCAAC 5'. What is the most likely effect this mutation will have on the organism.
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The organism will develop abnormally, because this mutation introduces a frame shift.
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Evaluate the statements below and determine which is the best explanation for why bacteria don't use telomerase.
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Bacteria have circular chromosomes that do not shorten.
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The proofreading function of DNA polymerase reduces the error rate from about one in a million basepairs to about one in a ________ basepairs.
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Hundred million.
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DNA polymerases use their ________ activity to remove a mismatched basepair.
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3' -> 5' exonuclease.
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Proofreading by DNA polymerase involves the removal of
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several bases on the newly-synthesized strand of DNA.
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If an organism had a DNA polymerase III that lost its ability to proofread, which of the following statements would be TRUE?
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The mutation rate for the organism would increase, and more substitutions would be seen in its DNA than in an organism that had functional proofreading.
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Which of the following is NOT a mechanism that cells use to ensure their DNA is accurately replicated?
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When mismatched nucleotides are detected, DNA polymerase will begin to synthesize DNA in the 3' to 5' direction to correct the mistake.
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Which of the following prevents supercoiling of the DNA strands ahead of the replication bubble?
answer
Topoisomerase.
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A child has a disease that is causing severe growth delays and rapid aging. His cells are assayed, and it is noticed that there is a severe decrease in DNA synthesis compared to normal cells. When DNA from his cells was gently heated to separate the double helix, numerous, small, single-stranded fragments of about 1000 base pairs were found. Which enzyme is likely to be defective in this child?
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Ligase.
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Which of the following synthesizes the daughter strands during DNA replication?
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DNA polymerase.
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Why is the lagging strand synthesized in a discontinuous fashion?
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DNA synthesis must occur in a 5' to 3' direction, which imposes spatial constraints on the synthesis of the lagging strand.
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Which of the following statements is TRUE?
1. DNA polymerase is capable of synthesizing DNA without attaching the incoming nucleotide to a pre-existing, free, 3' hydroxyl group
2. Primase, an RNA polymerase, is capable of synthesizing RNA without attaching the incoming nucleotide to a pre-existing, free, 3' hydroxyl group
3. Once helicase has initially opened up the DNA double helix, it dissociates from the molecule allowing single stranded binding proteins and DNA polymerase to bind
4. DNA polymerase incorporates new nucleotides into the growing DNA molecule by forming hydrogen bonds between complementary nucleotides on opposite strands of the double helix.
5. Only the lagging strand requires the enzyme primase
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2. Primase, an RNA polymerase, is capable of synthesizing RNA without attaching the incoming nucleotide to a pre-existing, free, 3' hydroxyl group.
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The genetic material in bacteria is
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Double stranded DNA.
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DNA replication in bacteria begins at
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a single origin and proceeds in both directions.
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DNA replication is said to be
answer
semi-conservative.
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How is bacterial DNA replication different from eukaryotic DNA replication?
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Bacterial DNA replication moves out from the origin of replication in two directions, while eukaryotic DNA replication moves out from the origin of replication in only one direction.
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How is bacterial DNA replication similar to eukaryotic DNA replication?
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Both bacterial and eukaryotic DNA replication is semiconservative.
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The correct structure of DNA monomers can be presented as
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phosphate-sugar-base.
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Which of the following DNA molecules is the most stable?
answer
GCGTGCAC
CGCACGTG
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What statement about the major and minor grooves is TRUE
answer
The major and minor grooves are important for DNA binding proteins to attach to the DNA.
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Which of the following statements about the DNA double helix is TRUE?
answer
Complementary base pairing across the double helix allows information to be transferred via RNA transcription and DNA replication.
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