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Genetics, (on a molecular level such as the Nitrogen Bases) was one of my Favorites in my Honors Bio. class. mrgreen

@Hikari: Hair Color is Determined(I'm pretty sure) By multiple Alleles on diferent Chromosomes, so it's Difficult to say it's something simple like Incomplete or Co dominance. And because it's on multiple Alleles We Can't make those fancy little punnet square things, not even one of the 4 by 4 punnet squares.

Ah a subject I know well as a 5th year genetics Ph.D student... I certainly have a passion for it. The most facinating part of Genetics as a subject, to me and what got me into the field, is that organisms are what they are due to a simple code made up of 4 nitrogenous bases (A,T,C,and G). Amazing! Just 4 bases, strung together and we get the myriad of life that we see on our planet today.
@tikiboy and Hikari: Human hair color is complex and, more specifically, is mostly a quantitative trait (usually seen as QTL, many genes/loci are involved to make a visible phenotype). QTL's are complicated and are non-Mendelian traits (no simple inheritance here!).
@Ang Yi: What assay are you doing with the X-gal and HIV infection of cells? I probably shouldn't pry as it is your research, I'm just curious as I've only done cloning and used lacZ as a marker for positive gene insertion.
@MustangDragon: What you described is a founder effect, and I've heard of that before. You can see this in many inbred populations unfortunately, that lack of a big gene pool is detrimental.
@Emily's_Gone_Mad: Ah the genetically engineered food debate is hot one and there is alot of misinformation being spread around (mostly from Green Peace and other non-govermental organizations). I suggest reading up on the actual science of GE agriculture, Biofortified.com is a blog made by graduate students that provides an unbiased, scientific opinion of alot of the nonsense out there on GE. All in all, the study that your teacher was probably talking about was one funded by Green Peace (or the like) and they most likely fed the rats more than they would ever encounter in nature and it wasn't statistically signficant from the controls as rat weight is highly variable, even when fed on a normal diet.