system
Given the following post, respond as if you're commenting on Reddit:
human
Never thought about Grad School before but now I'm interested in something pretty specific and think it might be worth a PhD...

I really just need to pitch this thought off some people in-the-know who can set the record straight.  I'm really interested in a topic that seems like it'd be worth it to pursue a PhD in.  I'm interested in big data/machine learning in regards to genomics and its applicability to medical marijuana.  How do I get a PhD in this?  Where do I even start?  All I have is a Bachelor's degree.  Do I need to find an institution that is slightly relevant?  Find a professor in a relevant field who can help/mentor?  Can I even pick a topic of interest and pursue it?  Are PhDs not really like this?  Are they more strict/structured than what I'm thinking?  Sorry for the dumb questions but googling most of this just brings up the scare articles about how people shouldn't go for PhDs...  Not very informative about the inner workings of it all.

*****
**Editing to add:** BS in Computer Science, currently work at an R1 institution in the US in their IT department.  Tuition assistance covers 1/2 the cost of grad courses.
gpt
If you have a computer programming background and foundational coursework in either biology or statistics, you may be competitive for a PhD program in computational biology or something similar. However, your research interest is currently too specific and needs to be more generalized. Specifically, you should be saying that you are:    
"interested in big data/machine learning in regards to genomics and its applicability to ~~medical marijuana~~ human health."