Abacterial cell usually contains a single loop of dna that is located in the cytoplasm of the cell and is not surrounded by a nuclear membrane. some bacteria have additional loops of dna called plasmids. plasmids can be used for genetic engineering because dna from other organisms can be spliced into a plasmid loop. for example, scientists in the late 20th century discovered a way to insert the portion of human dna that codes for the protein insulin into the plasmid of e. coli bacteria. which statement best explains why these genetically modified bacteria have been useful to society?

Genetically modified bacteria (recombinant bacteria) with the human gene for insulin is useful because after it’s being put in fermentation tank it starts to produce human insulin protein. The process of making recombinant bacteria includes DNA cloning.

A target gene, in this case, insulin gene, is inserted into a circular piece of DNA called a plasmid via restriction enzymes and DNA ligases. Recombinant DNA  is then introduced into bacteria via a process called transformation. With the right conditions the bacteria that contains the human insulin gene, will start transcribing the gene and translating the mRNA to produce many molecules of human insulin protein.

i think a) betsy can donate only blood to mark is correct because, mark and betsy have the same blood type. whereas nobody else has b+ blood so betsy can't donate to them.

substitution is the answer in this case