Case Study in Muscular Dystrophy
Q1: At first glance, which DNA difference can you immediately eliminate as causing DMD
in Liam? Explain your answer. 2 points
At first glance, the DNA difference located on Intron 4 can be immediately eliminated as
the cause for DMD in Liam. This is because introns get spliced out and they also don’t code for
proteins.
Q2: You take a closer look at the second genetic difference between Elijah and Liam. What
kind of mutation is this called? Why or why not can you eliminate mutation 2 from the
possible causes of DMD? 2 points
The second genetic difference between Elijah and Liam is called a silent mutation. We
are able to eliminate mutation 2 as a possible cause of DMD in Liam because even though the
codon in the amino acid sequence is changed, the final codon still codes for the same amino acid.
This means that the final product remains unchanged.
Q3: You take a closer look at the fifth difference. What kind of mutation is the fifth
difference? 1 point
The fifth difference is a missense mutation since the codon was changed and coded for a
different amino acid.
Q4: What does the structures of these two amino acids indicate about how likely it is that
difference five is the causative site? 1 point
In Elijah, the codon was supposed to code for Asp (Aspartic acid), however, in Liam, the
codon codes for Glu(Glutamic acid) instead. These two amino acids are structurally and
biochemically similar, so it is not very likely that difference fice is the causative site for DMD.
Q5: Which of the provided data should you use to determine if the first difference is a likely
cause of DMD in Liam? 1 point
The data that should be used would be the Dystrophin Expression bar graph that shows
the normalized dystrophin mRNA levels in muscle. If the first difference is a likely cause of
DMD, then the mRNA levels would be different between Liam and Elijah. However, their
mRNA levels were similar, which means the promoter was probably unaltered.
Q6: Please describe what effect (if any) the third difference will have on DNA polymerase,
RNA polymerase and protein size. 3 points
DNA polymerase would not be affected by the third difference and will continue to read
through the nucleotide difference. Since the third difference codes for a premature stop codon,
RNA polymerase would read the premature stop codon and stop synthesis of the protein. This
would result in a smaller dystrophin protein size because synthesis of the protein is not finished.
Q1: At first glance, which DNA difference can you immediately eliminate as causing DMD
in Liam? Explain your answer. 2 points
At first glance, the DNA difference located on Intron 4 can be immediately eliminated as
the cause for DMD in Liam. This is because introns get spliced out and they also don’t code for
proteins.
Q2: You take a closer look at the second genetic difference between Elijah and Liam. What
kind of mutation is this called? Why or why not can you eliminate mutation 2 from the
possible causes of DMD? 2 points
The second genetic difference between Elijah and Liam is called a silent mutation. We
are able to eliminate mutation 2 as a possible cause of DMD in Liam because even though the
codon in the amino acid sequence is changed, the final codon still codes for the same amino acid.
This means that the final product remains unchanged.
Q3: You take a closer look at the fifth difference. What kind of mutation is the fifth
difference? 1 point
The fifth difference is a missense mutation since the codon was changed and coded for a
different amino acid.
Q4: What does the structures of these two amino acids indicate about how likely it is that
difference five is the causative site? 1 point
In Elijah, the codon was supposed to code for Asp (Aspartic acid), however, in Liam, the
codon codes for Glu(Glutamic acid) instead. These two amino acids are structurally and
biochemically similar, so it is not very likely that difference fice is the causative site for DMD.
Q5: Which of the provided data should you use to determine if the first difference is a likely
cause of DMD in Liam? 1 point
The data that should be used would be the Dystrophin Expression bar graph that shows
the normalized dystrophin mRNA levels in muscle. If the first difference is a likely cause of
DMD, then the mRNA levels would be different between Liam and Elijah. However, their
mRNA levels were similar, which means the promoter was probably unaltered.
Q6: Please describe what effect (if any) the third difference will have on DNA polymerase,
RNA polymerase and protein size. 3 points
DNA polymerase would not be affected by the third difference and will continue to read
through the nucleotide difference. Since the third difference codes for a premature stop codon,
RNA polymerase would read the premature stop codon and stop synthesis of the protein. This
would result in a smaller dystrophin protein size because synthesis of the protein is not finished.
