What type of mutation results in the addition of extra genetic material?

The type of mutation that results in the addition of extra genetic material is duplication. In genetic terms, duplication refers to a segment of DNA being copied, leading to multiple copies of that particular segment within the genome. This increase in genetic material can affect gene dosage and, consequently, the organism's phenotype.

Duplication can occur in various ways, such as during DNA replication when errors happen, or through unequal crossing over during meiosis, where one chromosome may receive extra genetic information while the other loses it. Such mutations can have significant biological impacts, including developmental alterations or even contributing to evolutionary processes by providing additional genetic material for variation and selection.

In contrast, deletion mutations remove segments of genetic material, inversion mutations rearrange the order of genes within a chromosome without changing the amount of genetic material, and translocation mutations involve the rearrangement of genetic material between non-homologous chromosomes, which also does not create additional genetic material. Thus, duplication is the only option that directly leads to an increase in the amount of genetic material in the genome.