View Full Version : biology question

03-24-2008, 12:18 AM
Hello, everyone

If this is a repeat, I apologize, but I think I lost my connection while typing in my question.

I think I remember way back 100 years ago, in biology class, we determined that two blue-eyed people could not produce a brown-eyed child. We used a little chromozome chart, and I need to know what that thing was called?

Would appreciate anyone's expertise on this, and if I'm wrong about the eye color thing, please let me know that, too.

Thanks so much.


Mr Flibble
03-24-2008, 12:42 AM
Blue eyes are recessive, whilst brown eyes are dominant.

So two blue eyed people cannot have the brown eye gene to pass it on ( or they wouldn't be blue eyed, they'd be brown eyed).

However it is possible for two brown eyed people to hav a blue eyed child -- if they both have one recessive blue gene and one dominant brown gene

Mendel's punnett chart is probably what you are thinking of ( he used it for sweet peas) here (http://en.wikipedia.org/wiki/Image:Punnett_square_mendel_flowers.svg)

Capitol B = dominant, small b = recessive. All those with the capital( even just one) will exhibit the dominant gene, only the bb will show the recessive characteristic

If you have any type of dominant gene, it will take precendence, although the recessive can be passed on

03-24-2008, 01:26 AM
This theorem can also be used when determining which disorders and other afflictions can skip a generation, and which ones must have a direct tie to a parent.


03-24-2008, 04:12 AM
Thanks IRU - just can't type that name you've chosen! and Giusti, you've both been very helpful. I just didn't want to come across as a total nincompoop if I was wrong by some chance.

Sorry, IRU - your avatar reminds me so much of my niece - that's her attitude totally!

03-25-2008, 06:15 AM
However, two blue eyed people CAN have a green or hazel eyed child. The "true blue" recessive gene tends to be concentrated in peoples of Scandinavian and Norwegian descent. (There is more than one blue eye gene)

Melanie Nilles
03-25-2008, 06:46 AM
The chart is called a Punnet Square. And it's true that unless there's a mutation, two blue-eyed people can only produce blue-eyed children, because blue is recessive to brown.

This might help: http://www.athro.com/evo/gen/punnett.html

Edit: Ooh! and there's a link to more about human eye color examples if you scroll down to the bottom ;)

03-25-2008, 07:05 AM
There are at least 8 genes identified having to do with human eye color and that does not include the effects of epigenetics which can really play with your sense of understanding it all. The more we learn, the more we realize that we really don't know. There are several shades of "blue" or relative "blueness". Although it is very unlikely that 2 blue eyed people will have a brown / brownish eyed child it is not an iron clad lack of paternity suit. For undergrad biology your books will say that it can't happen, but in higher level study you will find that almost nothing is impossible; unlikely, yes, but not impossible.