Answer:
You could generate cDNA libraries and compare the transcribed regions of the genome
The answer is approximately 5 liters
The different barriers that you have to go through are the different organs of the immune system. These are the lymphoid organs, thymus, and bone marrow. The secondary wall that you have to go through are the lymphatic tissues which include the lymph nodes, adenoids, skin, liver, tonsils, spleen, and the lymph vessels.
At all times, these systems work hand-in-hand so that the body can protect itself in order for it to survive
I believe it is called a single displacement