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.
Following fertilization the embryonic stage of development continues until the end of the 10th week (gestational age) (8th week fertilization age). The first two weeks from fertilization is also referred to as the germinal stage or preembryonic stage.
