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SBI4U Mutations Worksheet - ANSWERS 1. Below is - robertschem

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SBI4U
Mutations Worksheet - ANSWERS
1. Below is the base sequence for the normal protein for normal hemoglobin and the base sequence for sick cell
hemoglobin.
Normal:
GGG CTT CTT TTT
Sickle:
GGG CAT CTT TTT
a. Write out the mRNA and polypeptide sequence resulting from this for both normal and sickle cell.
Normal mRNA: CCC GAA GAA AAA
Sickle mRNA: CCC GUA GAA AAA
Normal poly:
Sickle poly:
Pro - Glu - Glu - Lys
Pro - Val - Glu - Lyc
b. Identify this as a point or frameshift mutation. Explain your answer.
This is a point mutation because a point mutation is when one base pair is substituted for another. In
this question, the 5th base in the DNA sequence (thymine) is switched out for another (adenine). This substition
leads to a change in the amino acid sequence, which can
alter protein function. With respect to sickle cell
anemia, it has a drastic effect - this
change in amino acid reduces the hemoglobin's ability to bind with
oxygen.
c. If the original base sequence read GGG CTT CTT AAA instead, would this result in sickle cell anemia?
No, although there is a point mutation (one base pair group, TTT, is substituted for another, AAA). This
leads to a new amino acid (UUU = phenylaline) in the polypeptide
sequence. Sickle cell anemia is diagnosed
when there is a mutation in the 6th base pair,
resulting in valine instead of glutamate (glumatic acid). Either
way, this point mutation
may lead to malfunction of the protein in any case or possibly another disorder just not
sickle cell anemia.
2. There are several types of genetic mutations. List two. What do they have in common? How are they different?
Give an example of each.
Use your notes for this.
3. A geneticist found that a particular mutation had no effect on the protein coded by the gene. What do you think is
the most likely type of mutation in this gene? Why?
This is a silemt mutation because this mutation comes from a substitution of one base pair or base pair group
for another. However, this substitution still codes for the same amino acid. Protein is not changed and still
retains its original function.
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