And more specifically, there are six key factors that played a role in basically allowing this biotechnology field to actually arise. So let's briefly discuss what these six factors are and in the next several lectures we're going to take a look at these factors in much more detail. So let's begin with factor number one the existence of restriction enzymes. So restriction enzymes were essentially discovered and these biological molecules exist in bacterial cells and bacterial cells use these restriction enzymes to basically protect themselves from viral agents. So what these restriction enzymes do is they cleave DNA molecules or RNA molecules at specific locations at specific sites. And there are many different types of restriction enzymes also known as restriction and the nuclease that exist in nature.