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Genetic Engineering Exam #1 Questions with Complete Solutions
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Genetic Engineering Exam #1 Questions with Complete Solutions
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Genetic Engineering Exam #1 Questionswith Complete Solutions
Based only on what we have discussed so far, what is meant by the term "a tool of
molecular biology"? - Answer-different technologies and analyses used to provide
information about different organisms and processes within the field of molecular
biology
What chemical group is found at the 5' end of EVERY strand of a linear DNA molecule?
- Answer-phosphate group
What chemical group is found at the 3' end of EVERY strand of a linear DNA molecule?
- Answer-sugar group
What atoms make up the backbone of a strand of DNA? - Answer-alternating sugar and
phosphate groups
What is the difference between DNA breathing and DNA melting? - Answer-DNA
breathing is fluctuations of double stranded DNA helix that creates "bubbles" in the helix
where sections of base pairs are broken due to high temperatures or a denaturing
solvent, while the rest of the strand remains the same. The double stranded DNA does
not break in breathing and can resume its normal conformation because the H bonds
were not broken.
DNA melting is the denaturation of DNA in which the double strand completely unwinds
and separates, creating two separate single strands of DNA through the breaking of the
hydrogen bonds between the base pairs. DNA that has been melting cannot go back to
being a put-together double strand.
Using examples from class, give one example where breathing, melting, or the
differential flexibility of single-stranded or double-stranded DNA helps us understand the
mechanism underlying either an in vivo or an in vitro process or technique in molecular
biology - Answer-In investigation of lambda infection, the lambda genome exists as a
double stranded molecule within a phage and has cohesive ends that anneal to each
other immediately upon entering a cell. DNA melting was used to determine how the
DNA of this molecule is held together, as if it were only held together by hydrogen
bonds it expected the DNA would melt and become linear again, but this was not the
case and it immediately existed in a closed circle. This led to the discovery of DNA
ligase
How can we increase DNA breathing? - Answer-We can increase DNA breathing by
increasing and fluctuating temperatures (but still staying below melting temps), such as
in PCR, or exposing the DNA to a solvent while it is breathing
, Who does the double helix reform more quickly and more efficiently after the molecule
has been breathing, but not after it has been melted? - Answer-The hydrogen bonds
between the base pairs are not broken during breathing, but they are in melting. DNA
breathing also does not completely separate the strands, while DNA melting does
What is the definition of a promoter? - Answer-DNA sequences which determine where
transcription of a gene will begin by RNA Polymerase binding
What is the definition of a terminator? - Answer-DNA sequences which signal
termination of transcription by signaling RNA polymerase to stop
How does the term "Transcript" (or "mRNA") differ from the term "open reading frame" -
Answer-An ORF is the part of a gene that can be translated into a protein (encodes a
protein) and are preceded by a 5' UTR and followed by a 3' UTR. mRNA contains
regions that may or may not be part of protein coding sequences and is made up of a
transcribed region, promoter, terminator, and regulatory control elements
What do we mean when we say DNA replication is semi-conservative? - Answer-This
means that DNA replication occurs separately on each template strand in antiparallel
directions, so two copies of the original DNA are produced, each containing one original
strand and one new strand
What causes DNA to move from where it was put during gel electrophoresis? - Answer-
DNA is negatively charged, so when the electric current is applied to the gel, the DNA
will move toward the positive electrode on the other end of the gel
What causes DNA molecules to separate by size on electrophoresis begins (big
molecules of DNA have more charges so you might expect them to move faster than
small ones-but they don't. Moreover, objects are essentially mass-less in a buoyant
environment like a solution or a gel)? - Answer-Shorter strands move farther and
quicker to the positive electrode because there are more pores in the gel they can fit
through in comparison to the larger strands. Small and large molecules both have the
same charge to mass ratio
What causes DNA molecules to separate by topology once electrophoresis begins? -
Answer-More bendy molecules (typically longer) have more chances for each end to
bend into separate holes in the gel, getting hung up until one or the other is pulled out of
its hole and follows the other, slowing its process. Less bendy (shorter) molecules are
more likely to have both ends go through the same hole and be able to travel faster.
How do restriction enzymes differ from general nucleases? - Answer-A restriction
enzyme cuts DNA at specific sites recognized by the base sequences. Generic
nucleases will also removes bases and cut DNA, but do not recognize a specific
sequence or site to cut at
Draw a molecule cut by restriction enzyme - Answer-
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