Patho Practice Questions
Which bases are single-ringed structures in the DNA molecule?
a. Cytosine and thymine
b. Cytosine and adenine
c. Thymine and guanine
d. Guanine and adenine - ANSWER a. Cytosine and thymine
The single-ringed bases (pyrimidines) are cytosine and thymine. The double-ringed bases (purines)
are adenine and guanine.
The term describing the DNA subunit of one deoxyribose molecule, one phosphate group, and one
base is a:
a. polypeptide.
b. double helix.
c. nucleotide.
d. codon. - ANSWER c. nucleotide.
A nucleotide consists of one deoxyribose molecule, one phosphate group, and one base. The double
helix is the twisted staircase presentation of DNA that was proposed by Watson-Crick. A polypeptide
is a chain of proteins. A codon is a triplet of amino acids.
Which statement regarding codons is TRUE?
,a. There are 80 possible codons.
b. There are three codons that signal the end of a gene.
c. There are 70 codons that specify amino acids.
d. Each amino acid has one codon. - ANSWER b. There are three codons that signal the end of a
gene.
There are three codons that signal the end of a gene, and they are called termination or nonsense
codons. There are 64 possible codons, and 61 specify amino acids. There is more than one codon for
an amino acid.
The function of DNA polymerase is to:
a. synthesize RNA from the DNA template.
b. synthesize a polypeptide.
c. perform base-pairing in replication.
d. split DNA molecules. - ANSWER c. perform base-pairing in replication.
The function of DNA polymerase is to assist with base-pairing when replicating DNA. This enzyme
travels along the single DNA strand, adding the correct nucleotides to the free end of the new strand
and proofreading. TrANSWER cription is the synthesis of RNA from DNA and uses RNA polymerase.
TrANSWER lation is the formation of a polypeptide from RNA and does not require DNA polymerase.
An accurate description of a silent mutation is:
a. a change in the DNA without a change in amino acid.
b. insertion or deletion of one or more base-pairs.
,c. an increase in the number or frequency of mutations.
d. a mutation that occurs in the absence of exposure to a mutagen. - ANSWER a. a change in the
DNA without a change in amino acid.
A silent mutation occurs if a base-pair is changed but the DNA still codes for the same amino acid.
This is possible as amino acids have more than one codon (triplet) that codes for them. Insertion or
deletion of one or more base-pairs is a frameshift mutation and can change the entire reading
frame. A mutagen is an agent that increases the frequency of mutations. A spontaneous mutation
occurs when a mutation occurs but there is no exposure to a mutagen.
Base pairs are appropriately described as:
a. adenine pairs with guanine.
b. guanine pairs with thymine.
c. cytosine pairs with adenine.
d. uracil pairs with adenine. - ANSWER d. uracil pairs with adenine.
Uracil is structurally similar to thymine. Therefore, the correct base-pairs are adenine with thymine,
guanine with cytosine, and uracil with adenine.
The term describing the sequence for the beginning of a gene is:
a. intron.
b. exon.
c. promoter site.
, d. anticodon. - ANSWER c. promoter site.
The promoter site signals the beginning of a gene and is the location of the RNA polymerase binding.
Excised sequences are called introns. Exons are the portions of code that remain after introns are
excised, and they code for the actual proteins. The anticodon is the sequence of three nucleotides
that undergo complementary base-pairing in trANSWER lation.
Which chemical complex is secreted into the cytoplasm and synthesized in the nucleolus?
a. Endoplasmic reticulum
b. Cisternae
c. Ribosome
d. Lysosome - ANSWER c. Ribosome
The ribosomes are RNA complexes that are synthesized in the nucleolus and secreted into the
cytoplasm, possibly through pores in the nuclear envelope. Cisternae are tubular or sac-like channels
that extend throughout the cytoplasm. The endoplasmic reticulum is a membrane factory that
specializes in synthesis. Lysosomes are sac-like structures that originate from the Golgi complex.
Which is a characteristic of a somatic cell? A somatic cell:
a. contains three different cell types.
b. contains 46 chromosomes.
c. has gametes that are diploid cells.
d. contains diploid cells that are formed through meiosis. - ANSWER b. contains 46 chromosomes.
Which bases are single-ringed structures in the DNA molecule?
a. Cytosine and thymine
b. Cytosine and adenine
c. Thymine and guanine
d. Guanine and adenine - ANSWER a. Cytosine and thymine
The single-ringed bases (pyrimidines) are cytosine and thymine. The double-ringed bases (purines)
are adenine and guanine.
The term describing the DNA subunit of one deoxyribose molecule, one phosphate group, and one
base is a:
a. polypeptide.
b. double helix.
c. nucleotide.
d. codon. - ANSWER c. nucleotide.
A nucleotide consists of one deoxyribose molecule, one phosphate group, and one base. The double
helix is the twisted staircase presentation of DNA that was proposed by Watson-Crick. A polypeptide
is a chain of proteins. A codon is a triplet of amino acids.
Which statement regarding codons is TRUE?
,a. There are 80 possible codons.
b. There are three codons that signal the end of a gene.
c. There are 70 codons that specify amino acids.
d. Each amino acid has one codon. - ANSWER b. There are three codons that signal the end of a
gene.
There are three codons that signal the end of a gene, and they are called termination or nonsense
codons. There are 64 possible codons, and 61 specify amino acids. There is more than one codon for
an amino acid.
The function of DNA polymerase is to:
a. synthesize RNA from the DNA template.
b. synthesize a polypeptide.
c. perform base-pairing in replication.
d. split DNA molecules. - ANSWER c. perform base-pairing in replication.
The function of DNA polymerase is to assist with base-pairing when replicating DNA. This enzyme
travels along the single DNA strand, adding the correct nucleotides to the free end of the new strand
and proofreading. TrANSWER cription is the synthesis of RNA from DNA and uses RNA polymerase.
TrANSWER lation is the formation of a polypeptide from RNA and does not require DNA polymerase.
An accurate description of a silent mutation is:
a. a change in the DNA without a change in amino acid.
b. insertion or deletion of one or more base-pairs.
,c. an increase in the number or frequency of mutations.
d. a mutation that occurs in the absence of exposure to a mutagen. - ANSWER a. a change in the
DNA without a change in amino acid.
A silent mutation occurs if a base-pair is changed but the DNA still codes for the same amino acid.
This is possible as amino acids have more than one codon (triplet) that codes for them. Insertion or
deletion of one or more base-pairs is a frameshift mutation and can change the entire reading
frame. A mutagen is an agent that increases the frequency of mutations. A spontaneous mutation
occurs when a mutation occurs but there is no exposure to a mutagen.
Base pairs are appropriately described as:
a. adenine pairs with guanine.
b. guanine pairs with thymine.
c. cytosine pairs with adenine.
d. uracil pairs with adenine. - ANSWER d. uracil pairs with adenine.
Uracil is structurally similar to thymine. Therefore, the correct base-pairs are adenine with thymine,
guanine with cytosine, and uracil with adenine.
The term describing the sequence for the beginning of a gene is:
a. intron.
b. exon.
c. promoter site.
, d. anticodon. - ANSWER c. promoter site.
The promoter site signals the beginning of a gene and is the location of the RNA polymerase binding.
Excised sequences are called introns. Exons are the portions of code that remain after introns are
excised, and they code for the actual proteins. The anticodon is the sequence of three nucleotides
that undergo complementary base-pairing in trANSWER lation.
Which chemical complex is secreted into the cytoplasm and synthesized in the nucleolus?
a. Endoplasmic reticulum
b. Cisternae
c. Ribosome
d. Lysosome - ANSWER c. Ribosome
The ribosomes are RNA complexes that are synthesized in the nucleolus and secreted into the
cytoplasm, possibly through pores in the nuclear envelope. Cisternae are tubular or sac-like channels
that extend throughout the cytoplasm. The endoplasmic reticulum is a membrane factory that
specializes in synthesis. Lysosomes are sac-like structures that originate from the Golgi complex.
Which is a characteristic of a somatic cell? A somatic cell:
a. contains three different cell types.
b. contains 46 chromosomes.
c. has gametes that are diploid cells.
d. contains diploid cells that are formed through meiosis. - ANSWER b. contains 46 chromosomes.
