Name ______________________________________ Pd and Date _______________
Mutations
Below are two partial sequences of DNA bases (shown for only one strand of DNA) Sequence 1 is from a human and
sequence 2 is from a cow. In both humans and cows, this sequence is part of a set of instructions for controlling a
bodily function. In this case, the sequence contains the gene to make the protein insulin. Insulin is necessary for the
uptake of sugar from the blood. Without insulin, a person cannot use digested sugars the same way others can, and
they have a disease called diabetes.
For the following DNA sequences, make a complimentary RNA strand and determine which amino acids are
assembled to make the insulin protein in both the cow and the human.
Sequence 1:
Human
DNA: C C A T A G C A C G T T A C A A C G T G A A G G T A A
mRNA:
Amino Acids:
Sequence 2:
Cow
DNA: C C G T A G C A T G T T A C A A C G C G A A G G C A C
mRNA:
Amino Acids:
Analysis
1.
The DNA sequence is different for the cow and the human, but the amino acid chain produced by the
sequence is almost the same. How can this happen?
2. Could two humans (or two cows) have some differences in the DNA sequence for insulin, yet still make
exactly the same insulin proteins? Explain your answer.
Mutations
Diabetes is a disease characterized by the inability to break down sugars. Often a person with diabetes has a
defective DNA sequence that codes for the making of the insulin protein. Therefore, they do not properly make the
insulin protein. This mutation is called a POINT MUTATION because only one amino acid is affected.
3. Suppose a person has a mutation in their DNA, and the first triplet for the gene coding for insulin is CCC
(instead of CCA). Determine what amino acid the new DNA triplet codes for. Will this person be diabetic?
Amino Acid _____________________
4.
Diabetic?___________________
What if the first triplet was CAA (instead of CCA)
Amino Acid _____________________
Diabetic?___________________
Frameshift Mutations occur when a base is added (or removed) from a DNA/RNA sequence causing the rest of the
DNA sequence to be “moved” up or down one letter.
For questions 5-8, use the following DNA sequence to determine what type of mutation has occurred and list the
affect it has on the amino acid sequence (which means you will have to find the AA sequence for all of them .)
Correct DNA sequence: T A C A A A C C T A G T T T A T A G C C A T T C
mRNA:
Amino Acid chain
Correct DNA sequence: T A C A A A C C T A G T T T A T A G C C A T T C
DNA sequence:
mRNA:
Amino Acid chain
Type of mutation
AND affect on
amino acid
sequence (choose
one from each line)
DNA sequence:
mRNA:
Amino Acid chain
Type of mutation
AND affect on
amino acid
sequence (choose
one from each line)
DNA sequence:
mRNA:
Amino Acid chain
Type of mutation
AND affect on
amino acid
sequence (choose
one from each line)
DNA sequence:
mRNA:
Amino Acid chain
Type of mutation
AND affect on
amino acid
sequence (choose
one from each line)
5. T A C A A G C C T A G T T T A T A G C C A T T C
Point Mutation (substitution, addition or deletion)
Affect on AA Sequence: Silent, Nonsense, Missense, or Frameshift
Description of Affect: No change, Stops coding, Changes one AA, Changes entire AA sequence
following mutation.
6. T A C A A A C C C T A G T T T A T A G C C A T T C
Point Mutation (substitution, addition or deletion)
Affect on AA Sequence: Silent, Nonsense, Missense, or Frameshift
Description of Affect: No change, Stops coding, Changes one AA, Changes entire AA sequence
following mutation.
7. T A C A A A C C T A G T T A T A G C C A T T C
Point Mutation (substitution, addition or deletion)
Affect on AA Sequence: Silent, Nonsense, Missense, or Frameshift
Description of Affect: No change, Stops coding, Changes one AA, Changes entire AA sequence
following mutation.
8. T A C A A A A C T A G T T T A T A G C C A T T C
Point Mutation (substitution, addition or deletion)
Affect on AA Sequence: Silent, Nonsense, Missense, or Frameshift
Description of Affect: No change, Stops coding, Changes one AA, Changes entire AA sequence
following mutation.