# dominant traits **URL:** \ **Category:** Factual Questions\ **Created:** [July 17, 2000, 12:55pm UTC](https://boards.straightdope.com/t/dominant-traits/25828 "2000-07-17T12:55:41Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![truth091357](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@truth091357](https://boards.straightdope.com/u/truth091357)\ **Post date:** [July 17, 2000, 12:55pm UTC](https://boards.straightdope.com/t/dominant-traits/25828/1 "2000-07-17T12:55:41Z")
what is the probability of two brown eyed parents having a green eyed child? ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [July 17, 2000, 3:22pm UTC](https://boards.straightdope.com/t/dominant-traits/25828/2 "2000-07-17T15:22:08Z")
It depends on how often their mobile homes caught fire. But seriously, folks… Based on the info you gave it’s really not possible to give you a probability. First of all, eye color is a polygenic trait as far as I know. In other words there’s no single eye color gene. So that prevents us from doing the basic genetic probability check. Secondly, you only described the phenotype (appearance) of the parents and not the genotype. The genotype would indicate if either parent carried the genetic material allowing for the possibility that offspring could have green eyes. There really is no way to accurately compute this probability based on your information. ---
**Author:** ![maralinn](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@maralinn](https://boards.straightdope.com/u/maralinn)\ **Post date:** [July 17, 2000, 5:10pm UTC](https://boards.straightdope.com/t/dominant-traits/25828/3 "2000-07-17T17:10:10Z")
My guess is that if both parents have one green eye gene and one brown eye gene, then the odds are 1 in 4 that the child will have green eyes (because the child will have green eyes only if they get a green gene from both parents). But there’s no way to calcuate the “odds” that both parents have one of each gene, I don’t think. I would think that the majority of brown-eyed people have one brown and one blue gene, simply because blue eyes are so common. So we can probably conclude that the odds are kind of low that two people with the unusual combination of green/brown would marry each other. All just guesswork, of course. 🙂 ---
**Author:** ![tcburnett](https://avatars.discourse-cdn.com/v4/letter/t/c5a1d2/32.png) [@tcburnett](https://boards.straightdope.com/u/tcburnett)\ **Post date:** [July 17, 2000, 5:23pm UTC](https://boards.straightdope.com/t/dominant-traits/25828/4 "2000-07-17T17:23:14Z")
> [@](#): > > \*Originally posted by truth091357 \* > \*\*what is the probability of two brown eyed parents having a green eyed child? \*\* You are probably adopted. ---
**Author:** ![Jois](https://avatars.discourse-cdn.com/v4/letter/j/ea666f/32.png) [@Jois](https://boards.straightdope.com/u/Jois)\ **Post date:** [July 18, 2000, 12:18am UTC](https://boards.straightdope.com/t/dominant-traits/25828/5 "2000-07-18T00:18:30Z")
Before you ask for your adoption papers, search this forum for previous eye color threads. There are at least two. Try: eye color, blue eyes, green eyes, brown eyes, eye and hair color and one of those will get you to the right place. jois ---
**Author:** ![friedo](https://avatars.discourse-cdn.com/v4/letter/f/8edcca/32.png) [@friedo](https://boards.straightdope.com/u/friedo)\ **Post date:** [July 18, 2000, 12:49am UTC](https://boards.straightdope.com/t/dominant-traits/25828/6 "2000-07-18T00:49:49Z")
> [@](#): > > \*Originally posted by maralinn \* > \*\*My guess is that if both parents have one green eye gene and one brown eye gene, then the odds are 1 in 4 that the child will have green eyes (because the child will have green eyes only if they get a green gene from b > \*\* Heheheheh!! You said “green gene!” Ahem. Anyway…the simple dominant/recessive trick only works for brown and blue, as I recall, green, hazel, and gray involve other genes and is more complicated. ---
**Author:** ![Bear\_Nenno](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bear_nenno/32/3358_2.png) [@Bear\_Nenno](https://boards.straightdope.com/u/Bear_Nenno)\ **Post date:** [July 18, 2000, 12:54am UTC](https://boards.straightdope.com/t/dominant-traits/25828/7 "2000-07-18T00:54:40Z")
It is definately more complicated! We are not dealing with pea plants here people. ---
**Author:** ![Lance\_Turbo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lance_turbo/32/6156_2.png) [@Lance\_Turbo](https://boards.straightdope.com/u/Lance_Turbo)\ **Post date:** [July 18, 2000, 1:15am UTC](https://boards.straightdope.com/t/dominant-traits/25828/8 "2000-07-18T01:15:30Z")
Genetics guys have this two gene theory about eye color. One gene is green/blue the other brown/blue. Green is dominant over blue. Brown is dominant over blue. Brown is also dominant over green. This theory does not account for weird ass eye colors like gray and what not, but it’s a good start. Lets say: Mom is G-G on the green/blue gene and B-Bl on the brown/blue gene. Dad is G-G on the green/blue gene and B-Bl on the brown/blue gene. Both parents display brown eyes, and there is a 1 in 4 chance that junior is green eyed. ---
**Author:** ![Alphagene](https://avatars.discourse-cdn.com/v4/letter/a/8e7dd6/32.png) [@Alphagene](https://boards.straightdope.com/u/Alphagene)\ **Post date:** [July 18, 2000, 1:44am UTC](https://boards.straightdope.com/t/dominant-traits/25828/9 "2000-07-18T01:44:53Z")
That’s the first explanation of eye color that I’ve seen, Lance. Cool. Reminds me of Labrador retrievers, whose coat color depends on two genes. One determines pigment type (black is dominant, “chocolate” is recessive), the other determines whether or not that pigment will be deposited in the hairs (deposited is dominant over not deposited). Lack of pigment deposition produces golden labs. So color depends on both sets of genes. Once you start talking calico cats and _agouti_ mice, it gets even more complicated. The genetics of pigmentation in general is very complex. Recessive epistasis, modifer genes, suppressor genes, complementation, codominance and multiple alleles are all involved in pigmentation. It’s not just a case of one gene either being “on” or “off”. In other words, you get a damned ugly Punnett square. ---
**Author:** ![tcburnett](https://avatars.discourse-cdn.com/v4/letter/t/c5a1d2/32.png) [@tcburnett](https://boards.straightdope.com/u/tcburnett)\ **Post date:** [July 18, 2000, 2:08am UTC](https://boards.straightdope.com/t/dominant-traits/25828/10 "2000-07-18T02:08:25Z")
> [@](#): > > \*Originally posted by Bear\_Nenno \* > \*\*It is definately more complicated! We are not dealing with pea plants here people. \*\* Of course we are. Here is the site where you can breed your own peas online. These are green-eyed peas, but there are black-eyed peas as well. [http://www.sonic.net/~nbs/projects/anthro201/exper/](http://www.sonic.net/~nbs/projects/anthro201/exper/) Peas, brother -G. Mendel ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 18, 2000, 2:21am UTC](https://boards.straightdope.com/t/dominant-traits/25828/11 "2000-07-18T02:21:39Z")
> [@](#): > > \*Originally posted by Lance Turbo \* > \*\*This theory does not account for weird ass eye colors like gray and what not, but it’s a good start. > \*\* Or colors of normal ass eyes, either. That’s all I really had to say. I’m not up on my eye color genetics. ---
**Author:** ![Wood\_Thrush](https://avatars.discourse-cdn.com/v4/letter/w/b38774/32.png) [@Wood\_Thrush](https://boards.straightdope.com/u/Wood_Thrush)\ **Post date:** [July 18, 2000, 3:08am UTC](https://boards.straightdope.com/t/dominant-traits/25828/12 "2000-07-18T03:08:26Z")
> [@](#): > > \*Originally posted by tcburnett \* > \*\* > > > [@](#): > > > > \*Originally posted by Bear\_Nenno \* > > \*\*It is definately more complicated! We are not dealing with pea plants here people. \*\* > > Of course we are. Here is the site where you can breed your own peas online. These are green-eyed peas, but there are black-eyed peas as well. > > [http://www.sonic.net/~nbs/projects/anthro201/exper/](http://www.sonic.net/~nbs/projects/anthro201/exper/) > > Peas, brother > -G. Mendel \*\* **Bear\_Nenno** was correct. We are not discussing pea plants. **tcburnett** , tinker with [The Eye Color Calculator](http://www.athro.com/evo/gen/genefr2.html); it is more appropriate to this thread. From [the explanation for the Eye Color Calcuator](http://www.athro.com/evo/gen/inherit1.html): > [@](#): > > \*\*Eye color is more complex than two genes \*\* > > In humans three genes involved in eye color are known. They explain typical patterns of inheritance of brown, green, and blue eye colors. However, they don’t explain everything. Grey eye color, Hazel eye color, and multiple shades of blue, brown, green, and grey are not explained. The molecular basis of these genes is not known. What proteins they produce and how these proteins produce eye color is not known. Eye color at birth is often blue, and later turns to a darker color. Why eye color can change over time is not known. An additional gene for green is also postulated, and there are reports of blue eyed parents producing brown eyed children (which the three known genes can’t easily explain [mutations, modifier genes that supress brown, and additional brown genes are all potential explanations]). > > The known Human Eye color genes are: EYCL1 (also called gey), the Green/blue eye color gene, located on chromosome 19 (though there is also evidence that another gene with similar activity exists but is not on chromosome 19). EYCL2 (also called bey1), the central brown eye color gene, possibly located on chromosome 15. EYCL3 (also called bey2), the Brown/blue eye color gene located on chromosome 15. A second gene for green has also been postulated. Other eye colors including grey and hazel are not yet explained. We do not yet know what these genes make, or how they produce eye colors. The two gene model (EYCL1 and EYCL3) used above explains only a portion of human eye color inheritance. Both additional eye color genes and modifier genes are almost certainly involved. ---
**Author:** ![Needs2know](https://avatars.discourse-cdn.com/v4/letter/n/b5e925/32.png) [@Needs2know](https://boards.straightdope.com/u/Needs2know)\ **Post date:** [July 18, 2000, 11:54am UTC](https://boards.straightdope.com/t/dominant-traits/25828/13 "2000-07-18T11:54:00Z")
Are hazel eyes really that complicated? That’s interesting. Don’t many people who have blue/green hazel eyes have flecks of yellow in there that make them appear green when the light hits them right? I didn’t think it was all that genetically complicated. My daughter has strange colored eyes, so does my younger sister. Both of their fathers had dark green eyes and my mother and I have typical red/brown. Both my sister and my daughter ended up with this odd color that is much lighter, often photographs blue, looks green, turquoise or gray when you look straight at them. My neighbor who was Portugese called them tashelmara (unsure of spelling). Very interesting posts. Needs2know ---
**Author:** ![Jois](https://avatars.discourse-cdn.com/v4/letter/j/ea666f/32.png) [@Jois](https://boards.straightdope.com/u/Jois)\ **Post date:** [July 18, 2000, 4:09pm UTC](https://boards.straightdope.com/t/dominant-traits/25828/14 "2000-07-18T16:09:27Z")
Bless your heart, Wood Thrush, several of us have just worn our fingers to the bone 1. explaining that eyes aren’t single simple pea picking flower simple and 2. looking for a site with a reasonable explaination on the net. Thanks!