BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
1. In the experiment described that supports DNA as the genetic
material: Why does the mouse die if the researcher mixes the complete
dead pathogenic strain with live non-pathogenic strain bacteria and then
inject it into the mouse? - ANSWERS-Because the bacteria is able to
take up the DNA of the pathogenic S- strain, transforming the non-
pathogenic R-strain into the pathogenic form. The mouse would still die
if we destroyed polysaccharides, lipids, protein or RNA because we
could recover the S strain. With the sugar killed, the genetic component
was still present. All genetic components remain, and the R strain was
transformed into the S strain.
In the experiment described that supports DNA as the genetic material:
what was the only scenario in which the mouse lives? - ANSWERS-
When the DNA component was destroyed the mouse lived, because that
component contained the genetic material that allowed the bacterial
strain transformation.
What were the contributions of Wilkins, Franklin, Watson, and Crick to
the discovery of the structure of DNA? - ANSWERS-Maurice Wilkins
and Rosalind Franklin conducted experiments that provided data
showing the crystal structure of DNA using x ray crystallography
END OF
PAGE
1
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
James Watson and Francis Crick did not put forth their own
experimental data. Instead, they utilized data and DNA findings from
earlier researchers to develop the model of DNA. This model marked the
onset of extensive developments in molecular biology, and the two
scientists, along with Wilkins, were awarded the Nobel Prize for their
scientific contributions.
1. Based on the carbon numbering system for the sugar (1 - 5) that
makes up DNA, describe the main component that is attached to each
carbon and why it is important to the structure of DNA. - ANSWERS-a.
Carbon #1: Has the nitrogenous base attached. There are 2 groups of
nitrogenous bases: 1.) purines (2 rings; adenine and guanine) and 2.)
pyrimidines (1 ring; thymine (uracil in RNA) and cytosine). Adenine
and thymine (2 hydrogen bonds) and guanine and cytosine (3 hydrogen
bonds) base pair then to form double-stranded DNA.
b. Carbon #2: Determines if the sugar is ribose (RNA) or 2-deoxyribose
(DNA). A hydroxyl (-OH) at position #2 would indicate ribose and just a
hydrogen at position #2 would indicate 2-deoxyribose.
END OF
PAGE
2
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
c. Carbon #3: Always has a hydroxyl group attached whether DNA or
RNA. This hydroxyl group participates in the reaction required to build
nucleotide chains.
d. Carbon #4: Closes the ring structure of the 5-carbon sugar. Carbon #5
branches from Carbon #4 then.
e. Carbon #5: Has the phosphate group attached. This phosphate group
reacts with the Carbon #3 hydroxyl of another nucleotide to form a
phosphodiester bond and link nucleotides together (phosphate-sugar
backbone). In addition, the phosphate group is negatively-charged,
giving DNA its overall negative charge.
1. Describe why DNA has directionality. - ANSWERS-The first strand
starts from the 5' phosphate to the 3' hydroxyl. The second strand is
antiparallel. Antiparallel means that the strands run in opposite
directions.
1. What is the meaning of the term antiparallel in the structure of DNA?
- ANSWERS-antiparallel means that DNA is composed of two strands
of DNA that are running "side by side," yet due to their directionality
END OF
PAGE
3
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
they are each traveling in opposite directions, with the "bottom" of one
strand located across from the "top" of the other (DNA reads 5' à 3' with
5' containing free phosphate group and 3' containing free OH group)
What does the Meselson and Stahl experiment confirm? - ANSWERS-It
showed that DNA replication process was semi-conservative. It explains
that every new DNA double helix would be a hybrid that contains 2
strands; one strand of old DNA molecule base paired with the other
strand of newly synthesized DNA.
The major groove in the structure of DNA allows for more specificity in
binding proteins - ANSWERS-True
Eukaryotic DNA in the nucleus of cells will not supercoil since it is
linear. - ANSWERS-False - supercoil is possible because DNA is
associated with many proteins because these proteins limit its ability to
rotate
GC rich DNA has a lower melting temperature than AT rich DNA -
ANSWERS-false - it has a higher melting temperature
END OF
PAGE
4
QUESTIONS AND
ANSWERS 2026 - 2027
1. In the experiment described that supports DNA as the genetic
material: Why does the mouse die if the researcher mixes the complete
dead pathogenic strain with live non-pathogenic strain bacteria and then
inject it into the mouse? - ANSWERS-Because the bacteria is able to
take up the DNA of the pathogenic S- strain, transforming the non-
pathogenic R-strain into the pathogenic form. The mouse would still die
if we destroyed polysaccharides, lipids, protein or RNA because we
could recover the S strain. With the sugar killed, the genetic component
was still present. All genetic components remain, and the R strain was
transformed into the S strain.
In the experiment described that supports DNA as the genetic material:
what was the only scenario in which the mouse lives? - ANSWERS-
When the DNA component was destroyed the mouse lived, because that
component contained the genetic material that allowed the bacterial
strain transformation.
What were the contributions of Wilkins, Franklin, Watson, and Crick to
the discovery of the structure of DNA? - ANSWERS-Maurice Wilkins
and Rosalind Franklin conducted experiments that provided data
showing the crystal structure of DNA using x ray crystallography
END OF
PAGE
1
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
James Watson and Francis Crick did not put forth their own
experimental data. Instead, they utilized data and DNA findings from
earlier researchers to develop the model of DNA. This model marked the
onset of extensive developments in molecular biology, and the two
scientists, along with Wilkins, were awarded the Nobel Prize for their
scientific contributions.
1. Based on the carbon numbering system for the sugar (1 - 5) that
makes up DNA, describe the main component that is attached to each
carbon and why it is important to the structure of DNA. - ANSWERS-a.
Carbon #1: Has the nitrogenous base attached. There are 2 groups of
nitrogenous bases: 1.) purines (2 rings; adenine and guanine) and 2.)
pyrimidines (1 ring; thymine (uracil in RNA) and cytosine). Adenine
and thymine (2 hydrogen bonds) and guanine and cytosine (3 hydrogen
bonds) base pair then to form double-stranded DNA.
b. Carbon #2: Determines if the sugar is ribose (RNA) or 2-deoxyribose
(DNA). A hydroxyl (-OH) at position #2 would indicate ribose and just a
hydrogen at position #2 would indicate 2-deoxyribose.
END OF
PAGE
2
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
c. Carbon #3: Always has a hydroxyl group attached whether DNA or
RNA. This hydroxyl group participates in the reaction required to build
nucleotide chains.
d. Carbon #4: Closes the ring structure of the 5-carbon sugar. Carbon #5
branches from Carbon #4 then.
e. Carbon #5: Has the phosphate group attached. This phosphate group
reacts with the Carbon #3 hydroxyl of another nucleotide to form a
phosphodiester bond and link nucleotides together (phosphate-sugar
backbone). In addition, the phosphate group is negatively-charged,
giving DNA its overall negative charge.
1. Describe why DNA has directionality. - ANSWERS-The first strand
starts from the 5' phosphate to the 3' hydroxyl. The second strand is
antiparallel. Antiparallel means that the strands run in opposite
directions.
1. What is the meaning of the term antiparallel in the structure of DNA?
- ANSWERS-antiparallel means that DNA is composed of two strands
of DNA that are running "side by side," yet due to their directionality
END OF
PAGE
3
, BCH 5413 EXAM 1 LATEST
QUESTIONS AND
ANSWERS 2026 - 2027
they are each traveling in opposite directions, with the "bottom" of one
strand located across from the "top" of the other (DNA reads 5' à 3' with
5' containing free phosphate group and 3' containing free OH group)
What does the Meselson and Stahl experiment confirm? - ANSWERS-It
showed that DNA replication process was semi-conservative. It explains
that every new DNA double helix would be a hybrid that contains 2
strands; one strand of old DNA molecule base paired with the other
strand of newly synthesized DNA.
The major groove in the structure of DNA allows for more specificity in
binding proteins - ANSWERS-True
Eukaryotic DNA in the nucleus of cells will not supercoil since it is
linear. - ANSWERS-False - supercoil is possible because DNA is
associated with many proteins because these proteins limit its ability to
rotate
GC rich DNA has a lower melting temperature than AT rich DNA -
ANSWERS-false - it has a higher melting temperature
END OF
PAGE
4
