What do you guys think? I'll give you some time... here's some thinking music for ya'll. Hopefully you don't need all that time :-P
If you chose answer (2), you chose correctly my friend. It's actually pretty amazing, and pretty clever, that every single somatic (body) cell in the human body has the same genetic information (same exact DNA), but just differs in the expression (activation) of that information, depending on what type of cell it is. Think of it this way. All of the cells in your body (except gametes, which you shouldn't worry about now) use the same instruction booklet, and each cell has a whole copy of the booklet. However, your heart cells only use pages 5-6 of the book, while your lung cells only use pages 7-9. So while each cell contains the whole booklet, it only uses the part it needs to become/stay that specific type of cell.
With this in mind, answer (4) does not make sense, since heart and lung cells have the same amount of DNA molecules. Answer (1) is incorrect because it is only true for the lungs--the heart does not contain cells that make a hormone involved in respiration (breathing). Answer (3) is tricky because it seems similar to answer (2), the correct answer. But read closely...this answer talks about the "genetic code," which helps copy DNA bases and turn the message from DNA into protein (remember, DNA--->RNA--->Protein). Every cell uses the same code, not just one part of the code. It is the part of the DNA molecule used that changes between cells. Got it?
If you need more help, this site might provide a clearer explanation:
http://genetics.thetech.org/ask/ask4
And if you were wondering, yes, I did listen to that youtube video the whole time I made this post.
The music is a nice touch although I would have rather have this one: http://www.youtube.com/watch?v=q0s-1MC1hcE
ReplyDeleteI like your technique of thinking through the question and writing it down.