Usually, genes are transferred by bacteriophages, viruses that precisely takeover bacteria cells. Phages inject their own genetic material into the host cell like tiny syringes, compelling it to produce new phages. Throughout this occurrence, genes from the bacterial genome can be combined into the newly made phages. Subsequently, they inject their newly altered genetic load into other bacteria. By this, bacteriophages serve as a transportation, taking up DNA from one bacterium and leaving it into another. Bacteria can also connect through tiny connection tubes wherein they exchange pieces of DNA. They can take up genetic material from the environment as well. There are actually three ways for bacteria to transfer genes. The first one is called Conjugation, which is the transfer of DNA straight from one cell to another through cell-cell contact. Secondly, bacteria are adept at taking up DNA right from their environment and combining it into their genomes.This process is known as natural Transformation. Lastly, Transduction, wherein DNA is transferred from one cell to another by a virus.
The independent variable is "controlled" or held constant in the control group. A single experiment may include multiple experimental groups, which may all be compared against the control group. The purpose of having a control is to rule out other factors which may influence the results of an experiment.
