Gene mutations worksheet - Free Printable

Let me work through this step by step.

Part 1: Gene Mutations (frameshift insertion, frameshift deletion, substitution)

Normal DNA sequence: AAA ATG CTT CTC
Normal mRNA: UUU UAC GAA GAG
Amino acids: Phe - Tyr - Glu - Glu

Row 2:
DNA: AAA ATG TTT CTC
mRNA: UUU UAC AAA GAG
Amino acids: Phe - Tyr - Lys - Glu

Comparing to normal: The third codon changed from CTT→TTT in DNA (GAA→AAA in mRNA), changing Glu→Lys. This is a single base change within one codon. This is a substitution.

Row 3:
DNA: AAA ATG CCT TCT
mRNA: UUU UAC GGA AGA
Amino acids: Phe - Tyr - Gly - Arg

Comparing to normal: Normal DNA was AAA ATG CTT CTC. Now it's AAA ATG CCT TCT. Looking at the third position - there seems to be an extra C inserted. Let me look more carefully.

Normal: A-A-A | A-T-G | C-T-T | C-T-C
Row 3: A-A-A | A-T-G | C-C-T | T-C-T

Wait, let me recount. The normal has 4 codons of 3 bases = 12 bases total.
Normal DNA: AAA ATG CTT CTC (12 bases)
Row 3 DNA: AAA ATG CCT TCT (12 bases)

Hmm, but looking at the image description, row 3 shows "C C T T C T" with arrows indicating something. Let me reconsider.

Actually looking again at the image: Row 3 DNA appears to show AAA ATG C C T T C T with what looks like an insertion. The amino acids changed from Glu-Glu to Gly-Arg, which means the reading frame shifted.

If we insert a C after the second codon:
Normal: AAA ATG CTT CTC
With C inserted: AAA ATG C CTT CTC → AAA ATG CCT TCT C...

Wait that gives us AAA ATG CCT TCT which is 12 bases. But if we inserted one base, we'd have 13 bases. Let me look at the image more carefully.

Looking at the image: Row 3 shows DNA as "A A A | A T G | C C T | T C T" with arrows suggesting an insertion. The mRNA is "U U U | U A C | G G A | A G A".

If there's a frameshift insertion of C after position 6 (after ATG):
Original: AAA ATG CTT CTC
Insert C: AAA ATG C|C TT CTC → reading as AAA ATG CCT TCT C...

mRNA would be: UUU UAC GGA AGA G...
Amino acids: Phe Tyr Gly Arg...

This matches! So this is a frameshift insertion.

Row 4:
DNA: AAA TGC TTC TCC
mRNA: UUU ACG AAG AGG
Amino acids: Phe - Thr - Lys - Arg

Normal: AAA ATG CTT CTC
Row 4: AAA TGC TTC TCC

It looks like the first base of the second codon (A) was deleted:
Original: AAA A|TG CTT CTC
Delete A: AAA TG CTT CTC → AAA TGC TTC TC...

mRNA: UUU ACG AAG AG...
Amino acids: Phe Thr Lys Arg...

This matches! So this is a frameshift deletion.

Part 2: Point mutations (missense, nonsense, silent)

Original strand: AUG CCG UAU UAC GUA CCU UAA
Amino acids: Met Pro Tyr Tyr Val Pro STOP

Strand 2: AUG CCG UAU UAC GUU CCU UAA
Change: GUA → GUU (Val → Val)
Same amino acid = silent mutation

Strand 3: AUG UCG UAU UAC GUA CCU UAA
Change: CCG → UCG (Pro → Ser)
Different amino acid = missense mutation

Strand 4: AUG CCG UAU UAA GUA CCU UAA
Change: UAC → UAA (Tyr → STOP)
Creates premature stop codon = nonsense mutation

Let me verify my answers:

Part 1:
- Row 2: substitution ✓
- Row 3: frameshift insertion ✓
- Row 4: frameshift deletion ✓

Part 2:
- Strand 2: silent ✓
- Strand 3: missense ✓
- Strand 4: nonsense ✓