MMSC 491 QUIZ 1-4 QUESTIONS WITH VERIFIED
ANSWERS
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? - Answers - Guanine and
Uracil
Regarding the structure of bases in nucleic acids, which, if any, of the following
statements is incorrect? - Answers - Purines carry an amino group, unlike pyrimidines
True facts were:
-Pyrimidines have a single heterocylic ring consisting of four carbon atoms plus two
nitrogen atoms that are linked to the same carbonyl (-C=O) group
-Purines have two heterocyclic rings, each with two nitrogen atoms
-Thymine = 5-methyluracil.
Regarding the sugar residues in nucleic acids, which, if any, of the following statements
is incorrect? - Answers - The internal sugar residues in a DNA strand normally have free
hydroxyl groups, unlike those in an RNA strand.
Things that were correct:
-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
atom.
-Bases are covalently linked to the carbon 1? atoms of the sugars.
-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.
Regarding DNA replication, which, if any, of the following statements is incorrect? -
Answers - DNA replication is said to be semi-conservative because for each DNA helix
only one strand serves as a template for new DNA synthesis.
Correct facts:
-The two DNA strands of the parental DNA helix are unwound using a DNA helicase.
-The replication fork marks the point at which DNA is actively being replicated from a
single DNA duplex to form new DNA strands.
-The synthesis of new DNA strands always proceeds in the 5? ? 3? direction.
Regarding DNA replication and DNA synthesis, which, if any, of the following
statements is incorrect? - Answers - A DNA polymerase always requires a DNA
template to synthesize a complementary DNA.
, Correct Facts:
-The leading strand is replicated continuously.
-The lagging strand is replicated discontinuously: the new DNA is synthesized as short
pieces of DNA that must be ligated together.
-A DNA polymerase requires a short RNA primer when synthesizing new DNA strands
using a DNA template.
Which is the best definition of noncoding RNA? - Answers - A functional RNA that is not
translated to make a protein.
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. - Answers - 2n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2.`
Regarding the cell cycle, which, if any, of the following statements is correct? - Answers
- The M phase is the only phase in the cell cycle when chromosomes stained with
chemical dyes are visible under the light microscope.
Which of the following statements is incorrect? - Answers - The only structural
difference between DNA and RNA strands is that they have different sugars,
respectively deoxyribose and ribose.
Correct Facts:
-Nucleic acids are always negatively charged.
-Cellular DNAs are structured as a double helix.
-Cellular RNAs are single-stranded.
Which of the following statements is incorrect? - Answers - A-T base pairs are stronger
than G-C base pairs.
Correct Facts:
-Purines are nitrogenous bases with a double ring structure.
-Base pairs may form between bases on a single nucleic acid strand.
-Two types of stable base pairing occur in DNA but a third type of base pairing is
common in RNA-RNA and RNA-DNA base pairing.
Which of the following statements is incorrect? - Answers - Because centromeres and
telomeres are critically important for chromosome function their DNA has been very
highly conserved during evolution.
Correct Facts:
-Centromeres are important for correct segregation of chromosomes during cell division.
-The DNA of both centromeres and telomeres consist of repetitive DNA sequences.
-The DNA of our chromosomes may have multiple replication origins but their
sequences are not very well conserved.
ANSWERS
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? - Answers - Guanine and
Uracil
Regarding the structure of bases in nucleic acids, which, if any, of the following
statements is incorrect? - Answers - Purines carry an amino group, unlike pyrimidines
True facts were:
-Pyrimidines have a single heterocylic ring consisting of four carbon atoms plus two
nitrogen atoms that are linked to the same carbonyl (-C=O) group
-Purines have two heterocyclic rings, each with two nitrogen atoms
-Thymine = 5-methyluracil.
Regarding the sugar residues in nucleic acids, which, if any, of the following statements
is incorrect? - Answers - The internal sugar residues in a DNA strand normally have free
hydroxyl groups, unlike those in an RNA strand.
Things that were correct:
-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
atom.
-Bases are covalently linked to the carbon 1? atoms of the sugars.
-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.
Regarding DNA replication, which, if any, of the following statements is incorrect? -
Answers - DNA replication is said to be semi-conservative because for each DNA helix
only one strand serves as a template for new DNA synthesis.
Correct facts:
-The two DNA strands of the parental DNA helix are unwound using a DNA helicase.
-The replication fork marks the point at which DNA is actively being replicated from a
single DNA duplex to form new DNA strands.
-The synthesis of new DNA strands always proceeds in the 5? ? 3? direction.
Regarding DNA replication and DNA synthesis, which, if any, of the following
statements is incorrect? - Answers - A DNA polymerase always requires a DNA
template to synthesize a complementary DNA.
, Correct Facts:
-The leading strand is replicated continuously.
-The lagging strand is replicated discontinuously: the new DNA is synthesized as short
pieces of DNA that must be ligated together.
-A DNA polymerase requires a short RNA primer when synthesizing new DNA strands
using a DNA template.
Which is the best definition of noncoding RNA? - Answers - A functional RNA that is not
translated to make a protein.
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. - Answers - 2n chromosomes, DNA content of 2C in G1; 2n
chromosomes, DNA content of 4C in G2.`
Regarding the cell cycle, which, if any, of the following statements is correct? - Answers
- The M phase is the only phase in the cell cycle when chromosomes stained with
chemical dyes are visible under the light microscope.
Which of the following statements is incorrect? - Answers - The only structural
difference between DNA and RNA strands is that they have different sugars,
respectively deoxyribose and ribose.
Correct Facts:
-Nucleic acids are always negatively charged.
-Cellular DNAs are structured as a double helix.
-Cellular RNAs are single-stranded.
Which of the following statements is incorrect? - Answers - A-T base pairs are stronger
than G-C base pairs.
Correct Facts:
-Purines are nitrogenous bases with a double ring structure.
-Base pairs may form between bases on a single nucleic acid strand.
-Two types of stable base pairing occur in DNA but a third type of base pairing is
common in RNA-RNA and RNA-DNA base pairing.
Which of the following statements is incorrect? - Answers - Because centromeres and
telomeres are critically important for chromosome function their DNA has been very
highly conserved during evolution.
Correct Facts:
-Centromeres are important for correct segregation of chromosomes during cell division.
-The DNA of both centromeres and telomeres consist of repetitive DNA sequences.
-The DNA of our chromosomes may have multiple replication origins but their
sequences are not very well conserved.
