MOLECULAR DIAGNOSTICS EXAM
REVIEW QUESTIONS WITH COMPLETE
ANSWERS
DNA template in DNA replication - ANSWER-The order of nucleotides is maintained
during DNA replication because each strand of the parent double helix is the
template for a newly replicated strand.
In the process of replication, DNA is first unwound from the helical duplex so that
each single strand may serve as a template for the addition of nucleotides to the new
strand.
Fig 1.9 - ANSWER-Simultaneous replication of both strands of the double helix. Both
strands are read in the 3' to 5' direction. The lagging strand is read discontinuously,
with the polymerase skipping ahead and reading back toward the replication fork on
the lagging strand.
lagging strand and Okasaki fragments - ANSWER-Okazaki fragments, were the key
to explaining how both strands were copied at the replication fork.
Phosphodiester bonds - ANSWER-Nitrogen bases are attached to a deoxyribose
sugar, which forms a polymer with the deoxyribose sugars of other nucleotides
through a phosphodiester bond.
The hydroxyl group on the third carbon is important for forming the phosphodiester
bone that is the backbone of the DNA strand
nucleotides - ANSWER-Composed of a phophorylated ribose sugar and a nitrogen
base.
Each nucleotide consists of a 5 carbon sugar, the first carbon of which is covalently
joined to a nitrogen base and the fifth carbon to a phosphate moiety
nitrogen bases - ANSWER-Adenine, Thymine, Guanine, Cytosine
base pairing (purines and pyrimidines) - ANSWER-Nitrogen bases with a single ring
structure (thymine, cytosine) are pyrimidines.
Bases with a double ring structure (guanine, adenine) are purines.
hydrogen bonding of DNA - ANSWER-The formation of hydrogen bonds between
two complementary strands of DNA is called hybridization.
homologous DNA sequences Fig. 1.7 - ANSWER-Homologous sequences are not
identical and are oriented in opposite directions
PO 5 [GTAGCTCGCTGAT] 3' OH
, HO 3' [CATCGAGCGACTA] 5' OP
antiparallel - ANSWER-The sequences of the two strands that form the double helix
are complementary, not identical. They are in antiparallel orientation with the 5' end
of one strand at the 3' end of the other
DNA replication process Fig 1.8 - ANSWER-DNA synthesis proceeds from the 5'
phosphate group to the 3' hydroxyl group.
The template strand is copied in the opposite (3' to 5') direction.
The new double helix consists of the template strand and the new daughter strand
oriented in opposite directions from one another.
semiconservative - ANSWER-Semi-conservative replication is the key to maintaining
the sequence of the nucleotides in DNA through new generations.
Every cell in a multicellular organism or in a clonal population of unicellular
organisms carries the same genetic information. It is important that this information,
in the form of the DNA sequence, be transferred faithfully at cell division. The
replication apparatus is designed to copy the DNA strands in an orderly way with
minimal errors before each cell division.
DNA found in nature is mostly double-stranded. Two strands exist in an opposite 5'
to 3'/3' to 5' orientation held together by the hydrogen bonds between their
respective bases (A with T and G with C).
The bases are positioned such that the sugar-phosphate chain that connects them
(sugar-phosphate backbone) is oriented in a spiral or helix around the nitrogen
bases
leading strand orientation in DNA replication 5' to 3' - ANSWER-While DNA
replication proceeds in a continuous manner on the 3' to 5' strand, or the leading
strand, the replication apparatus jumps ahead a short distance (~1000 bases) on the
5' to 3' strand and then copies backward toward the replication fork.
DNA polymerase enzymes thus have the capacity to synthesize DNA in a 5' to 3'
direction and degrade DNA in both a 5' to 3' and 3' to 5' direction
5' and 3' ends of DNA, phosphate and hydroxyl groups - ANSWER-Nucleic acid is a
macromolecule made of nucleotides bound together by the phosphate and hydroxyl
groups on their sugars.
A nucleic acid chain grows by the attachment of the 5' phosphate group of an
incoming nucleotide to the 3' hydroxyl group of the last nucleotide on the growing
chain.
Addition of nucleotides in this way gives the DNA chain a polarity; that is, it has a 5'
phosphate end and a 3' hydroxyl end. We refer to DNA as oriented in a 5' to 3'
direction, and the linear sequence of the nucleotides, by convention, is read in that
order.
REVIEW QUESTIONS WITH COMPLETE
ANSWERS
DNA template in DNA replication - ANSWER-The order of nucleotides is maintained
during DNA replication because each strand of the parent double helix is the
template for a newly replicated strand.
In the process of replication, DNA is first unwound from the helical duplex so that
each single strand may serve as a template for the addition of nucleotides to the new
strand.
Fig 1.9 - ANSWER-Simultaneous replication of both strands of the double helix. Both
strands are read in the 3' to 5' direction. The lagging strand is read discontinuously,
with the polymerase skipping ahead and reading back toward the replication fork on
the lagging strand.
lagging strand and Okasaki fragments - ANSWER-Okazaki fragments, were the key
to explaining how both strands were copied at the replication fork.
Phosphodiester bonds - ANSWER-Nitrogen bases are attached to a deoxyribose
sugar, which forms a polymer with the deoxyribose sugars of other nucleotides
through a phosphodiester bond.
The hydroxyl group on the third carbon is important for forming the phosphodiester
bone that is the backbone of the DNA strand
nucleotides - ANSWER-Composed of a phophorylated ribose sugar and a nitrogen
base.
Each nucleotide consists of a 5 carbon sugar, the first carbon of which is covalently
joined to a nitrogen base and the fifth carbon to a phosphate moiety
nitrogen bases - ANSWER-Adenine, Thymine, Guanine, Cytosine
base pairing (purines and pyrimidines) - ANSWER-Nitrogen bases with a single ring
structure (thymine, cytosine) are pyrimidines.
Bases with a double ring structure (guanine, adenine) are purines.
hydrogen bonding of DNA - ANSWER-The formation of hydrogen bonds between
two complementary strands of DNA is called hybridization.
homologous DNA sequences Fig. 1.7 - ANSWER-Homologous sequences are not
identical and are oriented in opposite directions
PO 5 [GTAGCTCGCTGAT] 3' OH
, HO 3' [CATCGAGCGACTA] 5' OP
antiparallel - ANSWER-The sequences of the two strands that form the double helix
are complementary, not identical. They are in antiparallel orientation with the 5' end
of one strand at the 3' end of the other
DNA replication process Fig 1.8 - ANSWER-DNA synthesis proceeds from the 5'
phosphate group to the 3' hydroxyl group.
The template strand is copied in the opposite (3' to 5') direction.
The new double helix consists of the template strand and the new daughter strand
oriented in opposite directions from one another.
semiconservative - ANSWER-Semi-conservative replication is the key to maintaining
the sequence of the nucleotides in DNA through new generations.
Every cell in a multicellular organism or in a clonal population of unicellular
organisms carries the same genetic information. It is important that this information,
in the form of the DNA sequence, be transferred faithfully at cell division. The
replication apparatus is designed to copy the DNA strands in an orderly way with
minimal errors before each cell division.
DNA found in nature is mostly double-stranded. Two strands exist in an opposite 5'
to 3'/3' to 5' orientation held together by the hydrogen bonds between their
respective bases (A with T and G with C).
The bases are positioned such that the sugar-phosphate chain that connects them
(sugar-phosphate backbone) is oriented in a spiral or helix around the nitrogen
bases
leading strand orientation in DNA replication 5' to 3' - ANSWER-While DNA
replication proceeds in a continuous manner on the 3' to 5' strand, or the leading
strand, the replication apparatus jumps ahead a short distance (~1000 bases) on the
5' to 3' strand and then copies backward toward the replication fork.
DNA polymerase enzymes thus have the capacity to synthesize DNA in a 5' to 3'
direction and degrade DNA in both a 5' to 3' and 3' to 5' direction
5' and 3' ends of DNA, phosphate and hydroxyl groups - ANSWER-Nucleic acid is a
macromolecule made of nucleotides bound together by the phosphate and hydroxyl
groups on their sugars.
A nucleic acid chain grows by the attachment of the 5' phosphate group of an
incoming nucleotide to the 3' hydroxyl group of the last nucleotide on the growing
chain.
Addition of nucleotides in this way gives the DNA chain a polarity; that is, it has a 5'
phosphate end and a 3' hydroxyl end. We refer to DNA as oriented in a 5' to 3'
direction, and the linear sequence of the nucleotides, by convention, is read in that
order.
