Question

1. compare the two dna sequences and polypeptide chains they produce. what type of mutation has occurred to the bottom sequence?

a. substitution
b. insertion
c. deletion
d. no mutation
check answer
before mutations (normal)
t g t c t a c a t c g t a a c
acaggaugaggc a u g c
thr
asp
val
ala
leu
mutated sequence
t g t c t a c t c g t a a c g
acag a u g a g c a u g c
thr
asp
glu
his
cys

Explanation:

To determine the mutation type, we compare the DNA sequences (and corresponding codons/amino acids) before and after mutation. In the "Before Mutations" sequence, the codon for Val is "GUA", and in the "Mutated Sequence", the codon becomes "GAG" (for Glu), and subsequent codons shift. This indicates an insertion: an extra nucleotide is added, shifting the reading frame (frameshift mutation). Substitution changes one base (no frame shift), deletion removes a base (frame shift but shorter), and no mutation would have identical sequences. Here, the frame shift and new codons suggest insertion.

Answer:

B. Insertion