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MEDT491 Exam 1

Terms in this set (32)

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
C
Regarding the structure of bases in nucleic acids, which, if any, of the following statements is incorrect?

a) 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

b) Purines have two heterocyclic rings, each with two nitrogen atoms

c) Thymine = 5-methyluracil.

d) Purines carry an amino group, unlike pyrimidines
D
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 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 neighbour.
B
Regarding 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.
A
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.
C
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.
D
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.
D
Regarding the cell cycle, which, if any, of the following statements is correct?

a) The M phase and the S phase are the critically important phases of the cell cycle;
according to circumstance, the G2 phase and the G1 phase are dispensable.

b) The M phase is the only phase in the cell cycle when chromosomes stained with chemical
dyes are visible under the light microscope.

c) The G0 phase is a specialized phase that allows terminally differentiated cells to
irretrievably exit the cell cycle and become post-mitotic cells.

d) The G0 phase is a modified version of the G2 phase.
B
Regarding exons, which, if any, of the following statements is correct?

a) Some exons in protein-coding genes consist of noncoding DNA.

b) The first exon of a protein-coding gene always contains the translational start site.

c) The last exon of a protein-coding gene always contains the normal termination codon.

d) A coding exon is always translated in just one of the three possible forward reading
frames.
A
Regarding the structures of amino acids, which, if any, of the following statements is incorrect?

a) The general formula for a nonionised amino acid is H2N-CH(R)-COOH, that is, a central
carbon atom is linked to an amino group, a carboxyl group, a hydrogen atom, and a side
chain, R.

b) The identity of the amino acid is determined by the side chain that is connected to the
central carbon atom.

c) The side chain of an amino acid is based on a branch that contains one or more carbon
atoms

d) Proline is unique in having a side chain that is connected to both the central carbon and
also to the nitrogen atom of the amino group.
C
Regarding polypeptide structure, which, if any of the following statements is incorrect.

a) A polypeptide is a polymer composed of a linear sequence of amino acids.

b) A polypeptide normally adopts a rod-like conformation, with the side chains orientated in
the same direction relative to the polypeptide backbone.

c) The amino acids within a polypeptide are joined by a covalent bond known as a peptide
bond.

d) Peptide bonds form by a condensation reaction between the amino group of an amino
acid and the carboxyl group of its neighbor.
B
Regarding protein structure, which, if any, of the following statements is incorrect?

a) The primary structure is the linear sequence of amino acids.

b) The secondary structure is the path followed by the polypeptide backbone over its length.

c) The secondary structure of every protein contains an alpha-helix.

d) The structure of an alpha-helix is primarily determined by hydrogen bonding between
chemical groups on the side chains.
C, D
Which, if any, of the following statements is false?

a) Unlike DNA, RNAs are unmethylated, and only the four standard bases - A, C, G and U - are found in RNAs.

b) The primary structure of an RNA is the linear sequence of nucleotides.

c) The secondary structure of an RNA is dominated by hydrogen bonding between bases on
the same strand.

d) Stem-loop structures are common in RNA and consist of complementary sequences that
form stable base pairs, separated by a short sequence of unpaired bases.
A
Which, if any, of the following statements is false?

a) A ribosome is a large ribonucleoprotein that contains multiple different types of RNA but
just one type of protein.

b) During translation, a ribosome binds to the 5' end of a mRNA, slides along it until the
initiator AUG codon is identified, and continues until reaching an in-frame termination
codon.

c) The single type of ribosomal protein is a crucially important peptidyltransferase.

d) The peptidyltransferase catalyzes the condensation reaction that allows joining of amino
acids using peptide bonds.
A, C
Which, if any, of the following statements are false?

a) During translation, the individual codons of an mRNA are "read" by transient hydrogen bonding to a complementary anticodon sequence on a transfer RNA.

b) According to their anticodon, transfer RNAs usually have a specific amino acid attached to their 3' end.

c) When the anticodon of a tRNA binds to a codon with a suitably complementary sequence, the amino acid is released and becomes part of a polypeptide.

d) Translation terminates at an in-frame termination codon (UAA, UAG, or UGA in the universal genetic code) because for these codons, there are no transfer RNAs with a complementary anticodon sequence.
None
Which, if any, of the following statements are false?

a) Stem-loop structures are formed by base pairing of complementary sequences that are
separated by a short sequence of nucleotides with unpaired bases.

b) Stem-loop structures are common occurrences in both DNA and RNA.

c) Stem-loop structures are important for structural reasons only.

d) Stem-loop structures can be important functional elements.
B, C
Which, if any, of the following statements are false?

a) A naked DNA double helix has a stiff rod-like structure.

b) An RNA usually has a stiff rod-like structure, but occasionally has elements of secondary
structure caused by intrachain hydrogen bonding

c) Some proteins have stiff rod-like structures.

d) Some proteins have globular structures.
B
With respect to expression of an RNA gene, which, if any, of the following statements are false?

a) RNA processing sometimes includes RNA splicing

b) Regulatory antisense RNAs sometimes undergo splicing

c) Ribosomal RNAs and transfer RNAs are formed by cleavage of RNA precursors.

d) Ribosomal RNAs and transfer RNAs undergo base modification.
B
Roughly what percentage of our genome is made up of coding sequence?

a) 1%

b) 5%

c) 10%

d) 25%
A
In addition to coding sequence, which is generally very highly conserved, what additional percentage of our genome is highly to moderately conserved?

a) 0.4%

b) 4%

c) 14%

d) 24%
B
Roughly what percentage of our genome is made up of constitutive heterochromatin?

a) 0.7%

b) 7%

c) 27%

d) 57%
B
Roughly what percentage of our genome is made up of transposon repeats?

a) 0.45%

b) 4.5%

c) 25%

d) 45%
D
Which, if any, of the following statements are false?

a) The broadest definition of a pseudogene is any gene that has received inactivating
mutations and can no longer make a functional product

b) A retropseudogene is a non-functional cDNA copy of a processed RNA that has
integrated elsewhere into the genome.

c) A non-processed pseudogene is an inactive copy of a gene that has arisen by some type of
gene duplication.

d) An estimated 14,000 pseudogenes are found in the human genome.
A
Which, if any, of the following statements are false?

a) Constitutive heterochromatin remains highly condensed throughout the cell cycle.

b) Unlike constitutive heterochromatin, facultative heterochromatin describes chromatin that
can de-condense and behave as euchromatin under certain circumstances.

c) Most of the long arm of the Y chromatin is made up of constitutive heterochromatin.

d) In women one of the two X chromosomes in each diploid cell is heterochromatinised.
All are true
What is the approximate ratio between the DNA content of our nuclear genome and our mitochondrial genome?

a) 2,000:1

b) 20,000:1

c) 200,000:1

d) 2,000,000:1
C
Which of the following statements, if any, is false?

a) Amplifying DNA means making many identical copies of one or more starting DNA
sequences.

b) The object of DNA cloning is to amplify DNA.

c) The object of PCR is to amplify DNA

d) The object of DNA sequencing is to amplify DNA
D
Which of the following statements, if any, is false?

a) Amplifying DNA always requires a DNA polymerase.

b) Amplifying DNA must be carried out in bacterial or yeast cells.

c) DNA cloning in cells involves attaching the DNA to be cloned to a vector DNA to form a
recombinant DNA that may be circular or linear.

d) Vector molecules in DNA cloning must have a replication origin that confers the ability
B, D
Which of the following statements, if any, is false?

a) Cloning DNA in bacteria typically requires a plasmid or a bacteriophage vector.

b) Plasmids and bacteriophages are both small circular double-stranded DNA molecules.

c) Plasmids and bacteriophages each contain a replication origin that allows them to
replicate independently of the bacterial chromosome.

d) To be useful as vectors plasmids and bacteriophages need to be genetically modified.
B
Which of the following statements, if any, is false?

a) The polymerase chain reaction (PCR) is a cell-free method of DNA amplification.

b) PCR is usually used to amplify a specific DNA sequence of interest using oligonucleotide
primers that bind to closely flanking sequences.

c) PCR is superior to cell-based DNA cloning for two major reasons: it is much quicker and
it allows much greater DNA amplification.

d) PCR requires the use of a heat-stable DNA polymerase to make copies of the template
DNA.
C
With respect to nucleic acid hybridization, which, if any, of the following statements is false?

a) The probe is a labeled nucleic acid or oligonucleotide that is expected to hybridize to a
target DNA sequence within an unlabelled test nucleic acid population.

b) The probe is a known single-stranded nucleic acid or oligonucleotide that is intended to
hybridize to complementary target sequences in a poorly understood nucleic acid test
sample.

c) The object of a hybridization assay is to identify target sequences within a test sample
that are related to the probe so that some new information is gained about the target
sequences.

d) During a hybridization assay, a heteroduplex is formed by un-natural base pairing
between complementary probe and target sequences that show a sufficiently high degree of base pairing across part or all of their lengths.
A
With respect to nucleic acid hybridization, which, if any, of the following statements is false?

a) The strength of base pairing between a probe and a complementary target sequence
depends on the number of stable base pairs that are formed.

b) Among other parameters, the hybridization stringency depends on the salt concentration
and temperature of the hybridization reaction.

c) To identify a target sequence that is distantly related to the probe, high stringency
hybridization needs to be used.

d) Under conditions that favor low hybridization stringency long heteroduplexes with
significant base mismatching may be stable.
C
Nucleic acid hybridization assays are normally carried out under relaxed hybridization stringency (to maximize the chances of heteroduplex formation) but afterwards, washes are carried out that can be designed to favor perfectly matched sequences only by changing some parameter. Which, if any, of the following changes would be consistent with that aim?

a) An increase in temperature.

b) An increase in salt concentration.

c) An increase in the concentration of a polar molecule, such as urea or formamide.
A, C
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