Answer:
The correct answer is "horizontal gene transfer".
Step-by-step explanation:
The most common way at which genes are transferred is vertically, from parents to their descendants. However genes could be transferred among species, in what is known as horizontal gene transfer (HGT). HGT is most clearly seen in bacteria, actually HGT is the cause of the phenomenon of the development of antibiotic resistance. The theory of an ancient mitochondria moving their genes to the chromosomes of its host is most likely the result of HGT. This makes sense since an ancient mitochondria most likely behaved as an alpha proteobacteria, an ancient bacteria that already developed its HGT mechanism..