They contain extra genes... Idk what exactly but the bacteria is able to use these genes.
Mitochondrial DNA is passed down the maternal line so can be able to used to identify people in the same maternal line. As mtDNA does not undergo recombination and has very few mutations so can be used to trace back numerous generations. In the mitochondria themselves, they code for proteins needed for cellular respiration.
The DNA double helix is composed of two strands. One runs from 3' to 5' when unwound and is the leading strand. When DNA replication occurs the complementary strand is synthesised continuously. The other strand is the lagging strand and as the RNA primer joins to the 3' the new strand cannot be synthesised in the same direction as the leading strand. Instead it is synthesised in fragments, called Okazaki fragments, which are joined together by the enzyme Ligase.
I'm not sure why RNA primer is used instead but it is the made up of RNA (so has ribose sugar and uracil) instead of DNA (which has deoxyribose and thymine). Sorry!
Hope that helped.
Also, NK cells target virus effected cells while cytotoxic T-cells tend to target cancers and transplanted tissues.