Sunday, April 1, 2012

A is for Allele

An allele is defined as one form out of two of a gene that can either be inherited or achieved through a mutation. Each human has two alleles, one for each chromosome (humans have two of each chromosome). There are only two possible traits for an allele: positive or negative. Since everyone has two alleles, an individual with two positive alleles is termed homozygous dominant, an individual with one positive and one negative allele is termed heterozygous, and an individual with two negative alleles is termed homozygous recessive.



The way I was first taught to understand alleles was the blue eye/brown eye problem. Blue eyes are known to be recessive, brown eyes are known to be dominant. To have blue eyes, a person must be homozygous recessive or the trait will not be shown. Even one copy of the dominant allele gives rise to that trait. So that means if you have one recessive allele and one dominant allele, you will have brown eyes. If you have two copies of the dominant allele, you will still have brown eyes.

A lot of times this isn't the case with traits, multiple alleles are necessary for one single trait (like skin color).

PS: This is my first post for the A to Z Challenge, good luck to everyone who is participating!

12 comments:

Marian Allen said...

I love this stuff! I think it's so wacky that you can have both parents with dark hair and eyes and still be born with blond hair and blue eyes. People make such a big joke out of that, but genetics makes jokes of us all. :D

Looking forward to tomorrow!

Marian Allen
Fantasies, mysteries, comedies, recipes

Rachel said...

Love this. I forgot how much I love the genetics of science. I'm a creative writing major in college so not much science stuff for me!
I came over from the A-Z Blog challenge. I look forward to getting to know you through the challenge Jennifer. So glad to see another college kid! :-)

MynameisEarl said...

ARGH! You just reminded me of my high school biology class and how rowdy it was - the good kind.

I just found you on the A-to-Z list as well and was curious as to whether you really are a "Nice Girl" lol.

A Quiet Corner said...

Thanks for sharing! I inherited a blood disorder from one of my parents. However, since I never knew them, I've been unable to "blame" either!...:)JP

Hazel said...

This reminds me of my highschool science class! I've always found it amazing how a perfectly healthy person could be a carrier of a bad disease and then if they had a child with another carrier then their child would suffer from said disease!

Are green eyes dominent or recessive? Do you know? I've always wondered lol

Kristi Ann Hunt said...

Genetics was the best part of biology in high school! I never knew about the whole adeles thing though. That's interesting how multiple adeles are needed for things like skin color and the like. I guess that is why mixed race babies usually have skin color somewhere between the parents' colors, since it's not just a single setting but multiple ones.

Good stuff.

Gossip_Grl said...

Interesting post on this. On my dad's side there is one blue eyed child born every generation. While both my hubby and I have brown eyes we were blessed with the blue eyed child. :)
My sister was the blue eyed child and she had all dark eyed children. :)

Shaun_ShutterBug said...

This is so far out of my comfort zone of behind the camera its scary. I will however follow with the hope of learning something.
Your AtoZ buddy
Shaun
Valleys ShutterBug

Jennifer Macfarlan said...

Marian - I'm glad you liked it, thanks for stopping by!

Rachel - Woohoo another college student!! Thanks for taking time to stop by!

MynameisEarl - Well I hope your high school biology class was at least entertaining :)

A Quiet Corner - Sorry to hear about the blood disorder :( But technically you can blame both, if it was a recessive disorder both parents had to be carriers to have a child with the disorder.

Hazel - I have no idea if green eyes are dominant or recessive, unfortunately I haven't reached that level of genetics yet :( But you are so right about being a carrier, it's incredible

Kristi - I'm glad you enjoyed and learned something new!

Gossip_Grl - That's so interesting! Inheritance can work in mysterious ways sometimes

Shaun_ShutterBug - I hope I can teach you something interesting, thanks for stopping by!

The Hopeful Romantic said...

Woah! I need to get my sister to read this post - she LOVES bafling people with science. In your case, however, you've explained Allele very clearly. Is this going to be your theme for the challenger? I haven't yet settled on mine.

Good luck!

dirtylittlewhispers.com said...

I have blue eyes. I always look for men with blue eyes too to keep them going!

Suze said...

Interested enough in your 'B' to look at a back post. Looking forward to all of your posts, now. Superb theme.