in this video we're going to look at the role that monoclonal antibodies play in pregnancy tests if you're not sure what a pregnancy test is they generally look something like this and a cheap quick reliable way of finding out whether a woman's pregnant the key idea behind them is that pregnant women produce a hormone called hcg which is excreted in their urine and this little test kit is able to detect the hcg chemicals so by weighing on the test strip which is the orange beer to the end the test can tell a woman whether there's hcg in her urine and thus whether she's pregnant now exactly how the test works is a bit complicated so let's take a look at the test strip by itself without the plastic casing the strip has two important parts on the right side we have a bunch of monoclonal antibodies that are specific to hcg which means that they can bind to the hcg hormone if they come into contact with it and importantly these antibodies are fixed to the test strip so they can't move then on the left side we have the part where you we which contains blue beads covered in the same monoclonal antibodies as we saw on the right side so again these will be specific to hcg importantly though the beads and the antibodies they're attached to are completely free to move around they're not fixed to the strip if you wheel on the stick when you're not pregnant the urine will wash the unfixed beads along the test strip so they'll flow right over the fixed antibodies on the other part and nothing will happen so the test strip doesn't go blue however if you are pregnant and so your urine does contain hcg then that acg will bind to the antibodies on the blue beads so now when the blue beads flow over the test strip the hcg that they're carrying binds to the fixed antibodies as well and the beads get stuck in place by trapping loads of these tiny blue beads the entire strip appears blue and it's this blue strip that indicates a positive test result also we just want to point out that most pregnancy tests in real life actually have two lines rather than one with the second line acting as a controller so you normally need two lines for a positive result just remember that different tests do work differently though so just be sure to read the instructions before you use any anyways that's everything for this video so hope you found it useful and we'll see you again soon