Thursday, August 23, 2012

Our Little Pumpkin Head

Quick warning: this post may be a bit boring for those of you not interested in genetics or how genes are expressed.  Also, I don't understand it much myself so I may have over simplified it a bit or just plain gotten it wrong.

Oliver has red hair!

What!  How did that happen?  Since I always imagined having little brown-headed babies and Blob always imagined having little blond monsters running around, we were both surprised to learn that our baby is a ginger.   Because I can't help myself, I looked into how it works and what the chances of having a ginger muppet were.

I have brown hair.  Blob has blondish hair.  Before looking into this, I assumed that I was solely responsible Ollie's orangey-red locks since my mom has firey red hair and several other member of her family do as well.

But no!

Red hair is a recessive trait and needs two copies of the recessive allele to be expressed.  So in fact, both Blob and I had to contribute a recessive red allele.  We're both carriers!

The Red Hair Gene: MC1R (RR, Rr, rr)
The gene that determines whether or not someone has red hair is called MC1R (I have no idea why!). Let's call  the alleles "R" if it is dominant and "r" if it is recessive.  When it works, this gene creates a protein that converts hair color pigment from red to something else.

If a person does not have red hair, then at least one copy of the MC1R allele is on/working (R).  That means at least one or both parents contribute a working copy  (either Rr or RR genotype).  With one or more working alleles for the gene, a person can convert hair color pigment from red (pheomelanin) to not red (eumelanin).

If  each parent contributes a recessive allele (rr), the MC1R gene does not work.  Pigment stays red (pheomelanin).  So, all redheads have the genotype rr.

Pigment Bunches (pppppppp to PPPPPPPP)
Each person has 8 alleles that determine how dark his/her hair is.  We get 4 alleles that code for pigment from each parent.  The spectrum runs from the lightest light blonde hair, which is pppppppp, to really dark or black hair, which is PPPPPPPP.

Our Genotypes
My genotype for MC1R is Rr.  Since my mom is a readhead, she could only contribute a (r) recessive allele to me.  Since my hair is not red, I also have a working copy (R).  So, my genotype has to be Rr.  It's easy to tell with me because my dark hair is accompanied by red highlights and freckles.  I have dark-ish brown hair, so my pigment making bunch probably is either PPPPPppp or PPPPPPpp.


Blob's genotype for MC1R is Rr also.  We know his since our baby-thing has red hair (rr), but Blob doesn't have red hair.  That means that Blob has to be a carrier of the recessive trait (Rr) and passed his (r) recessive allele on to the baby thing.  It's a bit harder to tell that Blob is a carrier, but after doing a bit of reading, we learned that we should have been able to tell since his beard grows in with red hair.  Neither of Blob's parents have red hair either, so one of his parents also has to be a carrier of the recessive trait (Rr).  We're guessing it's probably his dad.  Rob has blondish hair, so his pigment making bunch probably is either PPpppppp or PPPppppp.

Oliver's MC1R genotype is rr.  We don't yet know what his pigment bunch looks like.  If he's a strawberry blonde, he'll have less pigment (e.g., PPpppppp).  If he has bright orangey hair, he'll have a split (e.g., PPPPpppp).  If he has auburn hair, it will be more like (PPPPPPpp).


Phew.  That's all the boring for a bit.  Here are some cute baby pictures.






And here is where most of my info came from:
http://www.thetech.org/genetics/ask.php?id=189

1 comment:

  1. Yay for a genetics lesson with cute baby pictures!

    ReplyDelete