Answer:
Insertion and Substitution
Step-by-step explanation:
During DNA replication, an Insertion is defined as an addition of one or more nucleotide to the DNA strand, during replication process. An obvious example is the process of insertion in microsatellite regions due to the DNA polymerase slipping.
While Substitution in DNA replication process is a term that describes the changing or substition or swapping of one or more nucleotide for another during DNA replication.
For example a change in a single "chemical letter" such as switching an A to a G, is a good example of substitution.
Hence, in this case, both Insertion and Substitution occured as GCAT got additional T chemical letter or nucleotide and which is described as Insertion.
While, there is also a change in position of C and A nucleotides, thereby forming GCTTA, which is termed as Substitution.