Practice Exam (Modules 6 & 7) - Unit 2 Flashcards
How did Avery, MacLeod, and McCarty contribute to our understanding of DNA?
a) determined that DNA contains four different nitrogenous bases
b) used X-ray diffraction to examine the structure of DNA
c) found that the phosphorus-containing components are the genetic material of phages
d) found that “the transforming principle” is DNA
e) discovered “the transforming principle” that could genetically alter bacteria
d) found that “the transforming principle” is DNA
A DNA molecule of 50 base pairs contains 15 cytosine bases (C). How many thymine bases will it have?
a) 60
b) 10
c) 30
d) 15
e) 35
Dr. LaRoche asked the BIOL 2030 COVID nine Team to isolate some nucleic acids from various sources: zebra fish nuclei (double-stranded DNA), picobirnavirus (double-stranded RNA), bidnavirus (single-stranded DNA), and RNA from HeLa cells for the miR-101 project (single-stranded RNA). Once extracted, each of these samples was in a different tube, but they were accidentally mixed up! This table gives a rough estimate of the nucleotide base makeup of each sample.
Tube A C U T G
1 32 17 0 32 19
2 34 16 15 0 35
3 30 21 0 26 23
4 33 16 34 0 17
Which extract MOST likely came from zebra fish nuclei?
a) Tube 1
b) Tube 2
c) Tube 3
d) Tube 4
a) Tube 1
Which of the following statements concerning the structure of DNA is INCORRECT?
a) The sequences of bases in the two strands are determined by noncovalent bonding between adenine and thymine or guanine and cytosine.
b) The backbone of each DNA strand is a repeating deoxyribose sugar-monophosphate polymer.
c) The planar bases stack on top of each other, perpendicular to the helix axis.
d) The B-DNA structure is a right-handed helix with 10 base pairs per rotation of the helix.
e) Antiparallel strands of DNA spiral around the helix axis means that both strands are running in the same direction.
e) Antiparallel strands of DNA spiral around the helix axis means that both strands are running in the same direction.
Consider two molecules of DNA. They are the same length, and they are both double-stranded. At 75°C, the first one will completely denature; however, at the same temperature the second one is still double-stranded. What factors might allow for these different melting temperatures?
a) The second molecule is in a solution with a higher salt content than the first molecule.
b) The first molecule has a secondary structure of B form, while the second molecule is an A form.
c) The first molecule is in a solution with a higher salt content than the second molecule.
d) The second molecule is methylated more than the first molecule.
a) The second molecule is in a solution with a higher salt content than the first molecule.
A molecule that consists of a nitrogenous base bonded to the 1’ carbon of a ribose or deoxyribose is a(n):
a) hairpin.
b) nucleoside.
c) polynucleotide.
d) isotope.
e) nucleotide.
b) nucleoside.
You’ve grown an overnight culture of bacteria in media that is enriched with radioactive nucleotides, so that both strands of every DNA molecule found in the bacteria will be radioactive. You harvest the cells and plan to grow them in new media with nucleotides that are NOT radioactive, so any DNA synthesized in this culture will not be radioactive. After the cells grow for two rounds of replication in the non-radioactive media, what proportion of DNA molecules will be radioactive?
a) 0
b) 1/8
c) 1/4
d) 1/3
e) 1/2
e) 1/2
What is the function of DNA gyrase?
a) Unwinds the double helix by breaking the hydrogen bonding between the two strands at the replication fork.
b) Prevents the formation of secondary structures within single-stranded DNA.
c) Connects Okazaki fragments by sealing nicks in the sugar–phosphate backbone.
d) Reduces coiling that builds up ahead of the replication fork as a result of unwinding.
e) Binds to origin of replication and causes a short section of DNA helix to unwind.
d) Reduces coiling that builds up ahead of the replication fork as a result of unwinding.
When replicating a chromosome, the synthesis of DNA is initiated from:
a) Deoxyribonucleotides
b) RNA template
c) DNA primer
d) 5’ phosphate
e) 3’ OH
Which of the following molecules is synthesized by a polymerase that uses DNA as a template and synthesizes the new strands in the 5’ to 3’ direction?
a) RNA only
b) both RNA and DNA
c) neither RNA nor DNA
d) DNA only
b) both RNA and DNA
Which of the following is NOT required for transcription?
a) RNA polymerase
b) Ribonucleoside triphosphates
c) Promoter
d) Helicase
e) DNA template
d) Helicase
Which of the following statements about RNA polymerase is NOT true?
a) RNA polymerase reads a template strand of DNA 3ʹ to 5ʹ.
b) RNA polymerase adds ribonucleotides to the 5ʹ end of a growing RNA molecule.
c) RNA polymerase has many subunits.
d) During transcription of a gene, RNA polymerase reads only one of two strands of DNA.
e) RNA polymerase binds to a promoter to initiate transcription.
b) RNA polymerase adds ribonucleotides to the 5ʹ end of a growing RNA molecule.
If the sequence of an RNA molecule is 5ʹ–CGCAUCGAUC–3ʹ, what is the sequence of the template strand of DNA?
a) 3ʹ–CGTCGATGCC–5ʹ
b) 3ʹ–GCGTAGCTAG–5ʹ
c) 5ʹ–GCGTAGCTAG–3ʹ
d) 3ʹ–CGCATCGATC–5ʹ
e) 5ʹ–CGCATCGATC–3ʹ
b) 3ʹ–GCGTAGCTAG–5ʹ
Fill in the blanks: When the RITS complex is present, the rate of mRNA synthesis _____ and the rate of protein production _____.
a) decreases; increases
b) increases; increases
c) increases; decreases
d) remains constant; increases
e) decreases; decreases
Which of the following IS a feature of the DNA sequence of some eukaryotic genes but would NOT be a feature of their mature mRNA molecules?
a) 3’ and 5’ untranslated regions and the protein-coding region.
b) Exons including the start and stop codons.
c) 3’ sequences involved in termination such as the cleavage site and the U-rich sequence.
d) The transcription start site.
e) The Rut site of genes with Rho-dependent terminators.
