Question

directions: transcribe and translate the original dna sequence (template strand is given). then, do the same for each mutated dna sequence. then, determine the consequence, if any, for each mutation, by circling your choice for each question.

original dna sequence: tac acc ttg gcg acg act att
mrna transcript:
amino acids:

mutated dna sequence: tac acc ttg gcc gac gac tat
mrna transcript:
amino acids:
type of mutation: (circle one) point or frameshift insertion or deletion or substitution
how will the mutation most likely affect the protein? (circle one) no change 1 amino acid changed premature stop signal no stop signal 1 amino acid added/deleted

Explanation:

Step1: Transcribe original DNA to mRNA

mRNA is complementary to DNA template strand: A↔U, T↔A, C↔G, G↔C.
Original DNA: TAC ACC TTG GCG ACG ACT ATT
mRNA: $AUG\ UGG\ AAC\ CGC\ UGC\ UGA\ UAA$

Step2: Translate original mRNA to amino acids

Use standard genetic code (AUG=Met, UGG=Trp, AAC=Asn, CGC=Arg, UGC=Cys, UGA/UAA=stop).
Amino acids: $Met-Trp-Asn-Arg-Cys-STOP$

Step3: Transcribe mutated DNA to mRNA

Mutated DNA: TAC ACC TTG GCC GAC GAC TAT
mRNA: $AUG\ UGG\ AAC\ CGG\ CUG\ CUG\ AUA$

Step4: Translate mutated mRNA to amino acids

Use standard genetic code (CGG=Arg, CUG=Leu, AUA=Ile).
Amino acids: $Met-Trp-Asn-Arg-Leu-Leu-Ile$

Step5: Identify mutation type

Compare original and mutated DNA: single base changes (GCG→GCC, ACG→GAC, ACT→GAC, ATT→TAT) are substitutions; no frameshift.
Mutation type: substitution (point mutation)

Step6: Determine protein effect

Mutated sequence changes 3 amino acids and removes stop signal, resulting in no stop signal and extended protein.
Protein effect: no stop signal

Answer:

Original Sequence Results

mRNA transcript: AUG UGG AAC CGC UGC UGA UAA
amino acids: Met-Trp-Asn-Arg-Cys-STOP

Mutated Sequence Results

mRNA transcript: AUG UGG AAC CGG CUG CUG AUA
amino acids: Met-Trp-Asn-Arg-Leu-Leu-Ile
Type of mutation: point (substitution)
How will the mutation most likely affect the protein?: no stop signal