What makes an Allele either dominant or recessive?

[BigToque]

Eg. brown eyes are dominant over blue eyes.

What makes brown dominant and blue recessive? Or do we not know this yet and just accept that genetics are like this?

 

[GasX]

Do you mean how do you know if a gene is dominant or recessive? Or do you mean what is the molecular action that makes one trait show up over another when both genes are present?

 

[DaveSimmons]

Depends on whether or not she's holding the whip

 

[BigToque]

Originally posted by: Mwilding
Do you mean how do you know if a gene is dominant or recessive? Or do you mean what is the molecular action that makes one trait show up over another when both genes are present?

Thats the one...

 

[GasX]

I don't know...

Maybe the resident molecular geneticist will chime in...

 

[KingNothing]

Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

 

[BigToque]

Originally posted by: KingNothing
Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

Blue eyes are always recessive. We talked about this in my biology class, the difference is that you are more likely to meet a person with 2 coppies of the blue allele. That's not the only reason, but it's basically just because the population with blue eyes is so large.

 

[SoylentGreen]

Originally posted by: KingNothing
Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

Swedes are a race?

 

[Ynog]

Originally posted by: Stefan

Originally posted by: KingNothing
Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

Blue eyes are always recessive. We talked about this in my biology class, the difference is that you are more likely to meet a person with 2 coppies of the blue allele. That's not the only reason, but it's basically just because the population with blue eyes is so large.

Eye color is much more complicated than people originally thought.
At the present time there are 3 pairs of gene that control our eye color, that scientists know of.
And through research they known that there must be more. Because the current model cannot
account for certain combinations and eye colors such as grey, hazel. Or how 2 blue eyed parents
can have a child with brown eyes.

 

[Borracho]

God

 

[GasX]

Originally posted by: KingNothing
Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

Mendel just rolled over in his grave...

 

[DrNoobie]

"Dominant" refers to an active gene / protein, the result of which contributes to the phenotype of the organism. Recessive disorders/traits tend to result from failures (mutations) in genes that code for enzymes or structural proteins. A person who has inherited the recessive gene from only one parent often shows dominant characteristics because the normal gene inherited from the other parent produces enough of the protein to serve the body's needs. In blood types, O is recessive, requiring both parents to be of the O-type. A is dominant and B is dominant, so you can have A-type, B-type, or AB-type (co-dominance).

 

[BigToque]

Originally posted by: Ynog

Originally posted by: Stefan

Originally posted by: KingNothing
Blue eyes aren't recessive for some races, like the Swedes. It just depends who your extended family has been breeding with.

Blue eyes are always recessive. We talked about this in my biology class, the difference is that you are more likely to meet a person with 2 coppies of the blue allele. That's not the only reason, but it's basically just because the population with blue eyes is so large.

Eye color is much more complicated than people originally thought.
At the present time there are 3 pairs of gene that control our eye color, that scientists know of.
And through research they known that there must be more. Because the current model cannot
account for certain combinations and eye colors such as grey, hazel. Or how 2 blue eyed parents
can have a child with brown eyes.

I just found this...

http://www.seps.org/cvoracle/faq/eyecolor.html

It's pretty interesting. Unfortunately for me (as I have blue eyes), blue is always recessive : I'm not even guarenteed a blue eyed kid even if my GF gives sends across her gene for blue eyes. (she's Brown eyed, but has an allele for blue).

 

[Ynog]

Personally when you get low level on why an particular gene is expressed over another I have no idea why. I just know
that when it comes to certain genes that a particular allele is the dominant one.

Because remember not all alleles have a dominant/recessive relationship. Blood for instance has a codominance, where you
can have a parent with the A allele and a parent with the B allele, and the resulting child will end up with AB blood.

 

[Ynog]

Originally posted by: Stefan

I just found this...

http://www.seps.org/cvoracle/faq/eyecolor.html

It's pretty interesting. Unfortunately for me (as I have blue eyes), blue is always recessive : I'm not even guarenteed a blue eyed kid even if my GF gives sends across her gene for blue eyes. (she's Brown eyed, but has an allele for blue).

Interestingly enough, one set of my grand-parents both have blue eyes. Yet they produced 3 daughters with blue eyes, and one with brown.
Normally one might think that the brown eyed child was from a different father, but the the brown eyed sister and one of the blue eyed sisters, my mother,
look so alike they are often confused as twins.

And my eye color has changed from a dark brown to a hazel. There is now distince green on the outside of my eyes.
Kind of weird.

 

[ThePresence]

My niece is blonde haired and blue eyed. BOTH of her parents have brown hair and eyes. Go figure.