My Page of Genetics -- A Collection of Research but mostly Theory

• Hair Color
• Eye Color
• Skin Color

Hello! This is my page dedicated to one of my favorite hobbies: researching and theorizing on the genetics of human coloration.

This is probably just a girl thing, but that's okay. At least once in a girl's (woman's--whatever) life, she thinks "I wonder what my kids will look like?" 'cause, let's face it, girls are still conditioned to desire a family of some sort sooner or later, though now it has become more acceptable for women to delay getting married and/or having a family until they have pursued a career and gained financial independence.

Anyway, once in a while, they'll wonder, and the study of genetics is the closest thing to answering their question(s). (That was a rather stange-souding sentence--sorry.)

I have two areas of particular intrest that are probably fairly common. People ask questions about them all the time, mainly because no one really knows the answers. Scientist have partially worked out the genetics of these things, but it will be many years before they will be able to fully explain them. These two things are red hair and green eyes. I do not have an intrest in explaining these two traits together. I only care about them separately. You'll see what I mean in a minute.



RED HAIR

Through my reseach I have discovered that red hair is caused by a mutation that caused the pigment phenomelanin to be produced instead of the usual eumelanin that causes coloration between blonde (suposedly) to black (I'm sure about that one). According to most web sites on red hair, it is inherited through an autosomal recessive mode, meaning an idividual must have two copies of the mutated gene in order to have red hair. Personally, I don't think it's that simple, and I'll show you why as soon as I make some tables for this page; meanwhile, you'll just have to read and think about it. Visualize when necessary.

Okay, first off, the autosomal recessive mode doesn't explain some of the most common forms of red hair, the "pseudo-reds," as I like to call them. The pseudo-reds include half-breed shades like strawberry blonde and auburn (red-brown) that are not actually red but red and another color blended together. According to the autosomal recessive mode that should never happen; blending is only supposed to occur in incomplete dominant and co-dominant modes. Actually, co-dominant doesn't blend, but expresses both traits at the same time like the roan coat color in cattle or in horses, but since human hair color is a little bit like a mosaic--I say mosaic because if you look at you hair, it's not just one solid color; you've got a lot that's one color, true, but there is also a variety of other shades mixed in--I beleive both modes are applicable. I'm sorry if that didn't make sense to you. You might have to read that a few times over to completely comprehend that overly nested sentence.

I experimented with a sex-linked red-head model for a short while because I had recently received a book about coat color genetics in cats and, in cats, red, or orange, fur was sex-linked, but, alas, it did not work for my human model pedigrees (meaning my preacher's family; eight children is certainly a sufficient number to conduct a survey over). True, an abnormal amount of males had red hair both in my theory and in my model, but it was passed from father to son, so, obviously, that didn't work. In a sex-linked recessive model only the girls would have a chance of gaining a red allele from their father. As far as I am aware, the mother in my model does not have any genes for red hair, but that, too, seems unlikely considering the profusion of red-heads among her children. And it is obvious through mere observation, that red hair is not dominant over any of the darker brown shades.

In my probably most cited example (see above), there are ten people, eight children ranging in ages from 19 to about 4 or 5, and two married adults. The father is--or rather was a red-head, which is a matter I will delve into shortly--and the mother has brown hair of an indeterminate shade. Of the children, six are boys and two are girls. One and only one boy has medium brown hair and the youngest girl has blonde hair with questionable red undertones. All the other children have or have had red hair of various shades, usually within the category of "orange," indicating that it is likely that none of the children possess two copies of the red-hair gene which agrees with my personal theory that the mother does not possess any red alleles.

Here is a Punnett Square for the straight forward Dominant-recessive model. B stands for brown shades. b stands for red. BB and Bb are phenotypically brown. bb is red.

__	B	b
B	BB	Bb
b	Bb	bb

This is the codominant/incomplete dominance model. BB is brown. RR is red and BR is red-brown or auburn.

__	B	R
B	BB	BR
R	BR	RR

This is the sex-linked recessive model.

__	XB	Xb
XB	XB XB	XB Xb
Y	XB Y	Xb Y

Back to my third paragraph on red hair; in most incidences, it is difficult to identify particular shades of red hair in adults because by the time they are in their 30's and 40's and have children usually their red hair has faded to an orange color, due to the protein being denatured by the sun's UV rays and age (most women know that red dye fades fastest of all other dyes; the hair is like this also), or has darkened to brown, making it impossible to completely determine their original hair color. I have tried looking at old photographs to help in the determining process, but lighting, clarity, and other factors such as dye interfere with a correct analysis.

I developed a numerical code for both eye color and hair color that seems to work fairly well. Admittedly, the hair color code works better than the eye color one as you will see if you keep reading. So, with the knowledge that I will certainly sound redundant later on in this page, I will tell you about the code.

In my code, hair color inheritance takes on the characteristics of all three non-sex-related inheritance patterns as you will soon see. This code is governed by numbers that represent different types and quantities of pigments. The averages of the numbers usually determine the shade.

The Code Basics:

1 = blonde
2 = red
3 = brown
4 = black

The genotypes and phenotypes:

11 - blonde
21 - orange/strawberry blonde
22 - red
31 - dark blonde/light brown
32 - red-brown
33 - brown
41 - brown
42 - dark red-brown*
43 - dark brown
44 - black

*The red coloring in the dark red-brown is often only seen in strong sunlight or if the hair has been bleached because the black pigment usually masks any of the red from visibly showing up. Oftentimes, dark red-brown appears to be just a slightly different shade of dark brown. This can happen to a lesser degree with the red-brown coloration.

__	4	2
3	43	32
1	41	21

Here is a Punnett Square for parents with 42 dark red-brown and 31 dark blonde/light brown. Their chilren are 43 dark brown, 41 brown, 32 red-brown, and 21 orange/strawberry blonde.

I've also played around with another type of model for pigmentation inheritance having to do with the density of the pigmentation withing the hair folicle. It's likely more acurate to how hair color is actually produced and inherited, but it still has many kinks in the system. Generally speaking, in this other model, there is one or more locus for determining the type of pigment, either eumelanin or phenomelanin, and other loci for determing the density of the deposit of melanin within the hair as it is being formed. The more dense the melanin, the darker and richer the hair color; the less dense, the lighter the hair color. The numberical assumes all this and translates it to an over-simplified number form. All numbers but 2 are symbolically eumelanin (2 being phonemelanin), with 1 being less dense than 4; however, density is left out within the phenomelanin range, or can be assumed to be the same as the eumelanin density.



GREEN EYES

The subject of green eyes is very confusing, mainly because "green" tends to be very subjective...as does "hazel." Often, people do not know how to distinguish between the two. I certainly haven't come up with a satisfactory explaination, but I preferr to say, just for the sake of arguement, that "green" eyes are over-diagnosed because of the culture's facination with the uniqueness and allure of that particular color; indeed, I would propose that many "green"-eyed people are, in actuality, hazel-eyed. Delusioned ones, please don't send me nasty e-mails; at this point in time, I do not delve into science but rather into personal observation and opinion. If you have read me much, you know I am rather contrary and don't care if I've offended you or not.

For clarification, when I refer to green eyes, I mean specifically eyes that are unquestionably green with little or no brown central ring (I have no idea what that's really called so I'll say BCR or CR), minimal brown flecking, and preferably a blue/green/grey or purple outer ring (also don't know the offical name if it has one, so it will now be known as OR). "Green" eyes with notable brown coloration I will refer to as "hazel" or more acurately "green-hazel," which I will explain in the next paragraph on blue eyes.

There isn't a name for the color of eyes I personally have. Apparently, it's disputed but I prefer to call them "blue-hazel" for a variety of reasons. First, they coloration does not fit in with the typical idea of blue eyes. True blues have little or no BCR, in fact true blues--at least the light, bright ones--should have a white or nearly white CR. It is my opinion, again, that most people categorized as "blue" are indeed blue-hazels. Blue-hazels have a light brown, gold, yellow, or yellow-green CR depending on how dark the main shade of blue is. Blue hazels also usually have a very distinctive dark blue/purple OR compared to the non-existant or faint OR of true blue eyes. When I use the term "hazel," generally I am referring to the fact that the said eye color has certain amounts of brown in it, such as a BCR or brown flecks. Hence, most green eyes are not actually green but are green-hazel, meaning they have brown in them.

Here are some pictures to demonstrate. No worries; I will label them so you won't be confused.



Here's a nice eye. I would consider this one to be grey or a light true blue.



And this one is a good hazel with an enormous BCR and brown streaking or radiants. This is actually a very hazelly blue, not a green. To tell, look at the OR and the iris color between the radiants.



This is an excellent picture of a true blue eye. There is no brown present whatsoever.



This is a lighter brown eye, obviously. Note the very dark OR however. That is a typical signature of brown eyes. This is actually a picture of a colored contact, but it does nicely for a visual explaination of light brown eyes.



This is a green-hazel eye. It has a notable BRC.



These eyes might actually be a very green hazel but from the picture, they look green enough. There is a dark green OR and what looks to be dark green flecking. The inner corners of the eyes look a little suspect though, but it could just be the lighting. Compare the differences between the green hazel eye and the "green" eyes. It's pretty drastic.


Because I was a very bored ninth grader or whenever that was, I came up with a very simple numerical "code," if you will, that determines eye color through use of a Punnett Square and a few simple rules. It's not always right, but it's more complicated than some of the examples of inheritance out there and explains a few more colors than just brown, blue, and green.

The Rules go like this:

• all properties are additive
• the bigger number always comes first
• the higher the number the more the pigment
• the averages usually determine the base color
• there are exceptions to every rule (I really mean that)

SKIN COLOR

Skin color inheritance is pretty simple compared to eye color and hair color. There's at least three loci for the genes for skin color and all they do is code for how much melanin a person has in their skin. Generally, it's an addtive property and doesn't have all this co-dom, incomp-dom, dom-rec stuff going on. Unless you get into the pheno and eumelanin expression, but that seems to mostly be a co-dom thing so no worries. Skin color isn't really my forte or my interest so I haven't done much research on that.