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.