Question

1. compare the two dna sequences and polypeptide chains they produce. what type of mutation has occurred to the bottom sequence?a. substitutionb. insertionc. deletiond. no mutationbefore mutations (normal)t g t c t a c a t c g t a a ca c a g a u g u a g c a u u gthr asp val ala leumutated sequencet g t c t a c t c g t a a c ga c a g a u g a g c a u u g cthr asp glu his cys

Explanation:

1. First, align the normal DNA sequence (T G T C T A C A T C G T A A C) with the mutated sequence (T G T C T A C T C G T A A C G).
2. Observe that at the 7th position, the normal sequence has an A, while the mutated sequence has a T. This is a single nucleotide change where one base is swapped for another.
3. Confirm the effect: this single base swap changes the corresponding codon (from UAU to UAG in mRNA, leading to Val → Glu) and causes a downstream shift in codon reading that changes all subsequent amino acids, which is consistent with a single base substitution altering the codon frame beyond that point.
4. Match to mutation types: Substitution is the replacement of one nucleotide with another, which matches this change. Insertion would add a base, deletion would remove a base, and no mutation would show identical sequences/amino acids, which do not fit.

Answer:

A. Substitution