Chapter 14: DNA Study Set

25 July 2022
4.7 (114 reviews)
44 test answers

Unlock all answers in this set

Unlock answers (40)
question
Which of the following data were available to Watson and Crick when they were trying to determine the structure of DNA? Check all that apply.
answer
YES: DNA is composed of 3 basic components: five-carbon sugars, phosphate groups, and 4 different nitrogenous bases. YES: In DNA, the proportion of adenine always equals that of thymine, and the proportion of guanine always equals that of cytosine. YES: X-ray diffraction patterns indicate that the DNA molecule has the shape of a helix. YES: In DNA, the predominant tautomeric forms of the nitrogenous bases contain keto and amino groups. YES: DNA always has an equal proportion of purines and pyrimidines.
question
Classify each item according to its role in DNA replication.
answer
Serves as a template for a new DNA molecule: -Parental DNA strands Building blocks needed to assemble a new DNA molecule: -Nucleoside triphosphates Enzymes required to replicate DNA: -DNA primase -DNA gyrase -DNA polymerases -DNA ligase -DNA helicase Not directly required for DNA replication: -Nucleoside monophosphates -Ribose
question
Match each enzyme with its function in E. coli.
answer
1. DNA Pol III is the main replication enzyme; it is responsible for the bulk of DNA synthesis. 2. DNA Pol I acts on the lagging strand to remove RNA primers and replace them with DNA. 3. DNA Pol II does not appear to play a role in replication but is involved in DNA repair.
question
Classify each characteristic according to whether it is found in prokaryotes only, eukaryotes only, both, or neither.
answer
PROKARYOTES ONLY: -The genome consists of one circular DNA molecule -There is a single origin of replication -The sliding clamp is composed of 2 identical subunits EUKARYOTES ONLY: -The sliding clamp is a trimer of the protein PCNA -The genome consists of multiple linear chromosomes -There are multiple origins of replication -Special regions called telomeres are replicated by telomerase rather than by the replisome -Primase is a complex of both an RNA polymerase and a DNA polymerase BOTH: -Replication is continuous along the leading strand and discontinuous along the lagging strand -Helicase unwinds and separates the 2 strands of DNA NEITHER: -New nucleotides are added to the 5' end of a growing strand -Ligase removes the RNA primers and replaces them with DNA -The leading strand is synthesized in short pieces called Okazaki fragments
question
If 28% of the DNA nucleotides from a certain organism contain the base T, what percent will contain the base G?
answer
22
question
During DNA replication, 32% of the nucleotides in one of the two template strands contain the base A. What percent of the nucleotides in the new strand that is made from this template strand will also contain the base A?
answer
32%
question
An organism is able to carry out normal DNA replication but cannot carry out excision repair of damaged DNA. One possible explanation is that this organism has a defective form of the enzyme
answer
DNA pol I.
question
The correct structure of DNA monomers can be presented as...
answer
phosphate-sugar-base.
question
Which of the following is a characteristic of double-stranded DNA?
answer
2 nanometers width, 10 base pairs per turn and 0.34 nanometers per basepair
question
Which of the following DNA molecules is the most stable?
answer
GCGTGCAC CGCACGTG
question
Why do complimentary nucleotides across the double stranded DNA bond together using hydrogen bonds rather than covalent bonds
answer
Covalent bonds would be too strong to allow the double helix to easily separate and make templates available for replication and transcription
question
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.
question
Which of the following statements about the DNA double helix is TRUE?
answer
Complimentary base pairing across the double helix allows information to be transferred via RNA transcription and DNA replication.
question
DNA replication is said to be...
answer
semi-conservative
question
Which of the following DNA sequences is complementary to 5' TAGAC 3'?
answer
5' GTCTA 3'
question
According to Chargaff's rule, which of the following statements about double-stranded DNA is TRUE?
answer
A = T and C = G and A + G = C + T
question
Evaluate the statements below and select the one that best explains why is the replication machinery found at the replication fork?
answer
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.
question
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?
answer
Because the structure of both G and A are similar in that they have a double ring
question
Which of the following prevents supercoiling of the DNA strands ahead of the replication bubble?
answer
topoisomerase
question
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?
answer
ligase!!!
question
Which of the following synthesizes the daughter strands during DNA replication?
answer
DNA polymerase
question
Why is the lagging strand synthesized in a discontinuous fashion?
answer
DNA synthesis must occur in a 5' to 3' direction, which imposes spatial constraints on the synthesis of the lagging strand.
question
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
answer
2,3,1,4
question
Which of the following is required to replicate the lagging strand of DNA?
answer
Okazaki fragments, primase and DNA ligase
question
RNA primers are removed by the action of the enzyme...
answer
DNA pol I.
question
DNA pol III can initiate DNA synthesis.
answer
FALSE!!!!
question
If DNA polymerase III could add nucleotides in either direction, Okazaki fragments would no longer form.
answer
True
question
The enzyme that unwinds a segment of the DNA molecule is...
answer
helicase.
question
The enzyme that travels along the leading strand assembling new nucleotides on a growing new strand of DNA is...
answer
DNA polymerase.
question
Before the lagging strand can begin assembling new DNA nucleotides, which of the following must occur?
answer
RNA primase constructs a short RNA primer.
question
If DNA ligase was nonfunctional, what would be a likely consequence?
answer
DNA replication would occur, but the lagging strand would be non-functional.
question
How do DNA polymerase I and DNA Polymerase III differ?
answer
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.
question
DNA polymerases cannot replicate...
answer
the 3' end of linear chromosomes.
question
Telomerase is unique because it contains...
answer
an RNA molecule!!!
question
Which of the following best describes the function of telomerase at the telomere?
answer
It adds new DNA to the longer strand of the telomere overhang.
question
What might be the consequence of an organism that was born without functional telomerase?
answer
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
question
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.
answer
The organism will develop abnormally, because this mutation introduces a frame shift.
question
Evaluate the statements below and determine which is the best explanation for why bacteria don't use telomerase.
answer
Bacteria have circular chromosomes that do not shorten.
question
The proofreading function of DNA polymerase reduces the error rate from about one in a million basepairs to about one in a ________ basepairs.
answer
hundred million
question
DNA polymerases use their ________ activity to remove a mismatched basepair.
answer
3' -> 5' exonuclease
question
Proofreading by DNA polymerase involves the removal of...
answer
several bases on the newly-synthesized strand of DNA.
question
If an organism had a DNA polymerase III that lost its ability to proofread, which of the following statements would be TRUE?
answer
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.
question
Which of the following is NOT a mechanism that cells use to ensure their DNA is accurately replicated?
answer
When mismatched nucleotides are detected, DNA polymerase will begin to synthesize DNA in the 3' to 5' direction to correct the mistake
question
DNA Polymerase uses what kind of enzymatic activity in the process of proofreading?
answer
YES: -5' to 3' exonuclease activity to remove the mismatched bases -5' to 3' polymerase activity to replace the excised bases