MMSC491 EXAM WITH CORRECT
ANSWERS 2026/EXAM PASS GUIDE
1. In a DNA double helix each type of base forms a stable base
pair with only one type of base. When bases on an RNA strand
are involved in base pairing, which bases can form stable base
pairs with more than one type of base?
A) Adenine and uracil
B) cytosine and uracil
C) guanine and uracil
D) uracil - ANSWER-guanine and uracil
2. Regarding the structure of bases in nucleic acids, which, if
any, of the following statements is incorrect?
A) Pyrimidines have a single heterocyclic ring consisting of four
carbon atoms plus two nitrogen atoms that are linked to the
same carbonyl group
B) Purines have two heterocyclic rings, each with two nitrogen
atoms
C) thymine = 5-methyluracil
, D pruines carry an amino group, unlike pyrimidines - ANSWER-
purines carry an amino group, unlike pyrimidines
3. Regarding the sugar residues in nucleic acids, which, if any, of
the following statements is incorrect?
A) The sugar is always based on a heterocyclic ring that consists
of one oxygen atom and four carbon atoms, one of which is
connected to a fifth carbon atom, the 5 carbon 5' carbon atom
B) The internal sugar residues in a DNA strand normally have
free hydroxyl groups, unlike those in an RNA strand.
C) Bases are covalently linked to the carbon 1' atoms of the
sugars.
D) Neighboring sugar residues are linked to each other by a
phosphodiester bond that connects the 3' carbon atom on one
sugar to the 5' carbon atom of its neighbor. - ANSWER-The
internal sugar residues in a DNA strand normally have free
hydroxyl groups, unlike those in an RNA strand.
4. Regarding the DNA replication, which, if any, of the following
statements is incorrect?
a. DNA replication is said to be semi-conservative because
for each DNA helix only one strand serves as a template
for new DNA synthesis.
b. The two DNA strands of the parental DNA helix are
unwound using a DNA helicase.
, c. The replication fork marks the point at which DNA is
actively being replicated from a single DNA duplex to
form new DNA strands.
d. The synthesis of new DNA strands always proceeds in the
5' → 3' direction. - ANSWER-a) DNA replication is said to
be semi-conservative because for each DNA helix only
one strand serves as a template for new DNA synthesis.
5. Regarding DNA replication and DNA synthesis, which, if any,
of the following statements is incorrect?
a. The leading strand is replicated continuously.
b. The lagging strand is replicated discontinuously: the new
DNA is synthesized as short pieces of DNA that must be
ligated together.
c. A DNA polymerase always requires a DNA template to
synthesize a complementary DNA.
d. A DNA polymerase requires a short RNA primer when
synthesizing new DNA strands using a DNA template. -
ANSWER-c) A DNA polymerase always requires a DNA
template to synthesize a complementary DNA.
6. Which is the best definition of noncoding RNA?
a. A mutant mRNA that is not capable of making a protein.
, b. Any RNA sequence that is not translated to make a
protein
c. Any RNA sequence in an mRNA, or in the primary
transcript used to make the mRNA, that is not translated
to make a protein.
d. A functional RNA that is not translated to make a
protein. - ANSWER-d) A functional RNA that is not
translated to make a protein.
7. If we take the number of chromosomes in a haploid sperm cell
or egg cell to be n and the total content of genomic DNA to be
C, what is the number of chromosomes and the total genomic
DNA content of a diploid G1 phase cell and in a diploid G2
phase cell from the same organism.
a. n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2.
b. 2n chromosomes, DNA content of 2C in G1; 4n
chromosomes, DNA content of 4C in G2.
c. 2n chromosomes, DNA content of 2C in G1; 4n
chromosomes, DNA content of 2C in G2.
d. 2n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2 - ANSWER-d) 2n
chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2
ANSWERS 2026/EXAM PASS GUIDE
1. In a DNA double helix each type of base forms a stable base
pair with only one type of base. When bases on an RNA strand
are involved in base pairing, which bases can form stable base
pairs with more than one type of base?
A) Adenine and uracil
B) cytosine and uracil
C) guanine and uracil
D) uracil - ANSWER-guanine and uracil
2. Regarding the structure of bases in nucleic acids, which, if
any, of the following statements is incorrect?
A) Pyrimidines have a single heterocyclic ring consisting of four
carbon atoms plus two nitrogen atoms that are linked to the
same carbonyl group
B) Purines have two heterocyclic rings, each with two nitrogen
atoms
C) thymine = 5-methyluracil
, D pruines carry an amino group, unlike pyrimidines - ANSWER-
purines carry an amino group, unlike pyrimidines
3. Regarding the sugar residues in nucleic acids, which, if any, of
the following statements is incorrect?
A) The sugar is always based on a heterocyclic ring that consists
of one oxygen atom and four carbon atoms, one of which is
connected to a fifth carbon atom, the 5 carbon 5' carbon atom
B) The internal sugar residues in a DNA strand normally have
free hydroxyl groups, unlike those in an RNA strand.
C) Bases are covalently linked to the carbon 1' atoms of the
sugars.
D) Neighboring sugar residues are linked to each other by a
phosphodiester bond that connects the 3' carbon atom on one
sugar to the 5' carbon atom of its neighbor. - ANSWER-The
internal sugar residues in a DNA strand normally have free
hydroxyl groups, unlike those in an RNA strand.
4. Regarding the DNA replication, which, if any, of the following
statements is incorrect?
a. DNA replication is said to be semi-conservative because
for each DNA helix only one strand serves as a template
for new DNA synthesis.
b. The two DNA strands of the parental DNA helix are
unwound using a DNA helicase.
, c. The replication fork marks the point at which DNA is
actively being replicated from a single DNA duplex to
form new DNA strands.
d. The synthesis of new DNA strands always proceeds in the
5' → 3' direction. - ANSWER-a) DNA replication is said to
be semi-conservative because for each DNA helix only
one strand serves as a template for new DNA synthesis.
5. Regarding DNA replication and DNA synthesis, which, if any,
of the following statements is incorrect?
a. The leading strand is replicated continuously.
b. The lagging strand is replicated discontinuously: the new
DNA is synthesized as short pieces of DNA that must be
ligated together.
c. A DNA polymerase always requires a DNA template to
synthesize a complementary DNA.
d. A DNA polymerase requires a short RNA primer when
synthesizing new DNA strands using a DNA template. -
ANSWER-c) A DNA polymerase always requires a DNA
template to synthesize a complementary DNA.
6. Which is the best definition of noncoding RNA?
a. A mutant mRNA that is not capable of making a protein.
, b. Any RNA sequence that is not translated to make a
protein
c. Any RNA sequence in an mRNA, or in the primary
transcript used to make the mRNA, that is not translated
to make a protein.
d. A functional RNA that is not translated to make a
protein. - ANSWER-d) A functional RNA that is not
translated to make a protein.
7. If we take the number of chromosomes in a haploid sperm cell
or egg cell to be n and the total content of genomic DNA to be
C, what is the number of chromosomes and the total genomic
DNA content of a diploid G1 phase cell and in a diploid G2
phase cell from the same organism.
a. n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2.
b. 2n chromosomes, DNA content of 2C in G1; 4n
chromosomes, DNA content of 4C in G2.
c. 2n chromosomes, DNA content of 2C in G1; 4n
chromosomes, DNA content of 2C in G2.
d. 2n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2 - ANSWER-d) 2n
chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2
