Question

When DNA replication occurs before meiosis, the original DNA strand CAG TGT CCG TAG is copied into complementary strand GTC CTA CGG ACA. What type of mutation has occurred?

Answer 1

The answer is inversion. 

According to the base pairing rules, in the DNA, base complements are adenine - thymine (A-T) and guanine - cytosine (G-C).

So, if the original strand is:                 CAG TGT CCG TAG
Then, its complementary strand is:    GTC ACA GGC ATC

If we compare complementary strand GTC ACA GGC ATC with mutated strand GTC CTA CGG ACA, we can conclude that first triplets GTC (three nucleotide bases) are the same in both strands. The problem are other triplets. If we take a close look, ACA GGC ATC is inverted CTA CGG ACA. So, in this example, inversion occurs. Inversion is a type of chromosome rearrangement in which chromosome segment is inverted end to end.