Bio 202 Exam 2 Question and Answer [2026] |
UPDATED ACTUAL Exam | Detailed Answer
Explanations
• Which enzyme catalyzes the addition of nucleotides to a growing DNA chain?
1. DNA polymerase
2. Helicase
3. Primase
4. Telomerase . CORRECT ANSWER: 1
• Which of the following statements about DNA replication is true?
1. DNA gyrase unwinds the DNA double helix.
2. Single-strand binding proteins stabilize the open conformation of the unwound DNA.
3. DNA polymerase adds dNTP monomers in the 3′-5′ direction.
4. Okazaki fragments are DNA fragments synthesized on the leading strand. .
CORRECT ANSWER: 2
Once helicase unwinds the double helix, single-strand binding proteins bind to the open
DNA and prevent it from winding together again.
• In 1928, Frederick Griffith conducted a series of experiments that demonstrated which
of the following?
1. DNA was a polymer composed of four repeating nucleotides.
2. A "transformation factor" could be released from one cell and picked up by another
cell, thus changing the genetic identity of the recipient cell.
3. DNA was localized to chromosomes.
4. Nuclei of white blood cells contain a weakly acidic substance, termed nuclein. .
CORRECT ANSWER: 2
He observed that a factor released from heat-killed SIII cells could transform non-lethal
RII cells into lethal SIII cells.
• Which of the following are classified as pyrimidines? . CORRECT ANSWER: thymine
and cytosine
• In 1944, Avery, Macleod, and McCarty provided direct evidence that DNA was the
hereditary molecule. They treated heat-killed extracts from lethal SIII bacteria with
various enzymes and found that transformation was prevented only upon treatment with
_______. . CORRECT ANSWER: DNase is an enzyme that degrades DNA. When
DNA was removed from the extract, non-lethal RII recipient cells were not genetically
transformed to the lethal SIII form.
, • Which of the following reagents is not required for the polymerase chain reaction?
1. Deoxynucleotide triphosphates
2. Dideoxynucleotide triphosphates
3. A pair of DNA primers
4. A heat-stable DNA polymerase . CORRECT ANSWER: 2
Dideoxynucleotides terminate chain elongation due to the absence of a 3'-OH group,
which is required for new nucleotide addition in the process of DNA replication.
Dideoxynucleotides are used in DNA sequencing reactions.
• Which of the following molecules is not required for a PCR reaction?
1. Ligase
2. DNA
3. Primer
4. DNTPs . CORRECT ANSWER: 1
Ligase is not required for a PCR reaction. The enzyme used during PCR is a
thermostable DNA polymerase.
• The thermostability of Taq polymerase is required during the annealing phase of PCR.
T/F? . CORRECT ANSWER: F
The annealing phase takes place at the lowest temperature of PCR. Taq polymerase is
derived from bacteria that live in hot springs, so the enzyme is thermostable, meaning
that its enzymatic properties can withstand the high temperatures needed for
denaturation.
• What is the purpose of raising the temperature to 90-95°C at the beginning of each
cycle of PCR?
1 To separate the double-stranded DNA
2 To extend the primer
3 To attach the primer
4 To renature two single DNA strands . CORRECT ANSWER: 1
The temperature is raised to denature the double-stranded DNA molecule into single
strands.
• The results of the Meselson-Stahl experiments relied on all of the following except
_______.
UPDATED ACTUAL Exam | Detailed Answer
Explanations
• Which enzyme catalyzes the addition of nucleotides to a growing DNA chain?
1. DNA polymerase
2. Helicase
3. Primase
4. Telomerase . CORRECT ANSWER: 1
• Which of the following statements about DNA replication is true?
1. DNA gyrase unwinds the DNA double helix.
2. Single-strand binding proteins stabilize the open conformation of the unwound DNA.
3. DNA polymerase adds dNTP monomers in the 3′-5′ direction.
4. Okazaki fragments are DNA fragments synthesized on the leading strand. .
CORRECT ANSWER: 2
Once helicase unwinds the double helix, single-strand binding proteins bind to the open
DNA and prevent it from winding together again.
• In 1928, Frederick Griffith conducted a series of experiments that demonstrated which
of the following?
1. DNA was a polymer composed of four repeating nucleotides.
2. A "transformation factor" could be released from one cell and picked up by another
cell, thus changing the genetic identity of the recipient cell.
3. DNA was localized to chromosomes.
4. Nuclei of white blood cells contain a weakly acidic substance, termed nuclein. .
CORRECT ANSWER: 2
He observed that a factor released from heat-killed SIII cells could transform non-lethal
RII cells into lethal SIII cells.
• Which of the following are classified as pyrimidines? . CORRECT ANSWER: thymine
and cytosine
• In 1944, Avery, Macleod, and McCarty provided direct evidence that DNA was the
hereditary molecule. They treated heat-killed extracts from lethal SIII bacteria with
various enzymes and found that transformation was prevented only upon treatment with
_______. . CORRECT ANSWER: DNase is an enzyme that degrades DNA. When
DNA was removed from the extract, non-lethal RII recipient cells were not genetically
transformed to the lethal SIII form.
, • Which of the following reagents is not required for the polymerase chain reaction?
1. Deoxynucleotide triphosphates
2. Dideoxynucleotide triphosphates
3. A pair of DNA primers
4. A heat-stable DNA polymerase . CORRECT ANSWER: 2
Dideoxynucleotides terminate chain elongation due to the absence of a 3'-OH group,
which is required for new nucleotide addition in the process of DNA replication.
Dideoxynucleotides are used in DNA sequencing reactions.
• Which of the following molecules is not required for a PCR reaction?
1. Ligase
2. DNA
3. Primer
4. DNTPs . CORRECT ANSWER: 1
Ligase is not required for a PCR reaction. The enzyme used during PCR is a
thermostable DNA polymerase.
• The thermostability of Taq polymerase is required during the annealing phase of PCR.
T/F? . CORRECT ANSWER: F
The annealing phase takes place at the lowest temperature of PCR. Taq polymerase is
derived from bacteria that live in hot springs, so the enzyme is thermostable, meaning
that its enzymatic properties can withstand the high temperatures needed for
denaturation.
• What is the purpose of raising the temperature to 90-95°C at the beginning of each
cycle of PCR?
1 To separate the double-stranded DNA
2 To extend the primer
3 To attach the primer
4 To renature two single DNA strands . CORRECT ANSWER: 1
The temperature is raised to denature the double-stranded DNA molecule into single
strands.
• The results of the Meselson-Stahl experiments relied on all of the following except
_______.
