DNA
DNA
Structure Replication
Biotech
Transcription Translation
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What are the three components of a
nucleotide?
Answer
•Sugar
•Phosphate
•Nitrogen base
Name the nitrogen bases in DNA
Answer
•Thymine
•Adenine
•Guanine
•Cytosine
Indicate the type and number of
bonds that hold the DNA strands
together
Answer
•Hydrogen bonds
•2 between adenine and thymine
•3 between guanine and cytosine
If the percentage composition of
adenine in a DNA molecule is 10%
then what are the percent
compositions of the other 3 bases.
Answer
•Thymine = 10%
•Guanine = 40 %
•Cytosine = 40%
What specific types of bond attaches
the nitrogen base to the sugar?
The phosphate to the sugar?
Answer
Nitrogen base + sugar = glycosyl
Phosphate + sugar = phosphodiester
Note: Both are covalent bonds!
What enzyme unwinds DNA at the
fork by breaking hydrogen bonds
between nitrogen bases?
Answer
helicase
What enzyme relieves stress further
up the fork?
Answer
DNA gyrase
What enzyme binds complimentary
bases and what direction does it
move? What has to be in place first
before this enzyme can bind to the
template?
Answer
DNA polymerase III which moves in a 5′
to 3′ direction. An RNA primer laid down
by RNA primase must be in place first.
What are the names of the fragments
of the sections on the lagging strand
and what enzyme joins these
sections?
Answer
Okazaki fragments are joined by
DNA ligase.
How does the fact that DNA
replicates semi-conservatively
decrease the possibility of errors
made during DNA replication?
You must first explain the term semiconservatively.
Answer
Semi-conservative replication means that each
parent strand serves as a template from which a
copy can be made. This template serves as the
checkpoint when DNA polymerase I and III
proofread the newly synthesized strand.
What molecular biology technique
would be the most appropriate for
analyzing the size of DNA
fragments?
Answer
Gel electrophoresis
What are three circumstances where
one might want to amplify the
amount of DNA by PCR?
Answer
Studying fossil remains
DNA found at scene of crime
Early diagnosis of disease (HIV)
Observe the following DNA
fingerprint and determine who
should remain a suspect.
Answer
JOHN
What does a restriction endonuclease
do?
Answer
Recognizes and cuts DNA at a specific
sequence.
How are recombinant bacteria
differentiated from the original
bacteria?
Answer
Recombinant bacteria also received a
marker gene (eg. Antibiotic
resistance) that allows them to be
easily distinguished when culturing.
Does transcription require a primer?
Answer
No
What must be recognized to initiate
transcription?
Answer
Promoter
What enzyme creates the mRNA
strand and what direction does it
move?
Answer
RNA polymerase synthesizes mRNA
in a 5′ to 3′ direction.
What is an intron?
An exon?
Which is removed by what enzyme?
Answer
Introns = non-coding regions of mRNA
Exons = coding regions of mRNA
Spliceosomes remove introns
What modifications must be made to
the ends of the mRNA transcript
before it can leave the nucleus and
why must these occur?
Answer
Cap – methyl guanine
Tail – Poly A tail by poly A polymerase
To prevent degradation by enzymes in the
cytoplasm
Where in the cell does translation
occur?
Answer
Cytoplasm at the ribosomes
What is necessary to initiate
translation? Indicate the specific
sequence of this initiator.
Answer
Start codon (AUG) on mRNA is
recognized by the ribosome.
Differentiate between a codon and
an anticodon.
Answer
Codon = 3 nucleotide bases on mRNA that
code for one amino acid
Anticodon = 3 nitrogen bases on tRNA that
are complimentary to the codon on mRNA.
What are the three types of RNA
and what are their functions in
translation
Answer
Messenger RNA – brings copy of gene to be read
Ribosomal RNA – reads or translates mRNA copy
by exposing 3 bases at a time
Transfer RNA – brings in amino acids to form
polypeptide
Which is more harmful; a
substitution or a deletion?