Question

part a
when dna replication occurs before meiosis, the original dna strand cag tgt tta tag is copied into complementary strand gtc aca ggc atc. what type of mutation has occurred?
a deletion
b insertion
c inversion
d substitution
part b
when dna replication occurs before meiosis, the original dna strand gtc aca ggc atc is copied into complementary strand cag ccg tag. what type of mutation has occurred??
a deletion
b insertion
c inversion
d translocation

Explanation:

• Part A:
• Deletion: A mutation where a nucleotide or a segment of DNA is removed. In the given problem, the original DNA strand has 4 triplets (CAG TGT TTA TAG) and the new strand also has 4 triplets (GTC ACA GGC ATC). So, no nucleotide is deleted.
• Insertion: A mutation where an extra nucleotide or segment of DNA is added. Since the number of triplets in original and new strand is same (4 triplets each), no insertion has occurred.
• Inversion: A mutation where a segment of DNA is reversed end - to - end. There is no indication of reversal of any segment in the given strands.
• Substitution: A mutation where one nucleotide is replaced by another. Here, in the third triplet, TTA (in original) is replaced by GGC (in new). So, substitution has occurred.
• Part B:
• Deletion: The original DNA strand (GTC ACA GGC ATC) has 4 triplets and the new strand (CAG CCG TAG) has 3 triplets. So, one triplet (the third triplet in original, which was GGC) has been deleted.
• Insertion: Since the number of triplets in new strand is less than the original, insertion is not the case.
• Inversion: There is no reversal of any segment of DNA.
• Translocation: A mutation where a segment of DNA is moved from one location to another (either within the same chromosome or to another chromosome). There is no such indication here.

Answer:

• Part A: D. substitution
• Part B: A. deletion