Genes and punnet squares?

Question

I'm having a baby in September, so just for fun I was doing punnet squares of my my traits and my partner's. After looking up dominant and recessive genes on the web I came to a realization: my mom has brown eyes and brown hair, and so do both of her parents and all of her siblings. My dad has blue eyes and red hair. My sister ended up with brown eyes and brown hair, but I have auburn hair and blue eyes. How can this be? Wouldn't my mother's genes have been dominant for me as well? Are those punnet squares even worth doing or are genetics all just a gamble?

Answer 1

Neither hair nor eye color is controlled by a single gene so you can't do a simple 4 x 4 punnett square for these traits.

For eye color, clearly your mother has the recessive alleles for both of the major genes involved (B & G) which is how you ended up bbgg.  (There are two genes involved and you have to be recessive at both to get blue eyes.)  This happened with me as well.  Everyone in my family has brown eyes and I have blue.

But, the basic answer is, yes, Punnett squares are worth doing but you happened to choose two traits that aren't monogenic so it's more complicated than it seems.

Answer 2

Punnett squares for hair color and eye color are difficult to predict.  These traits are controlled by more than one gene.  With that in mind, there is a lot of variability in each of these traits.  My parents: one has brown hair and green eyes and mom has black hair and brown eyes.  In 5 siblings: one with black hair, brown eyes, 2 with broan hair (brown and green eyes) and two with blond hiar (green and blue eyes).  So, parents looks will help, but your child could have totally different traits than you or your partner.  Other traits are easier to predict.  You just happened to pick two tough ones to predict.

Answer 3

The hair color is incomplete dominance.  So if there is a dominant and recessive gene together a totally different color results that is usually the middle between the two.  That is why your hair color is between red and brown, the chromosomes you received were dominant and recessive.  Of course, it is a lot more complicated then that, because many genes affect hair color, but that would explain your problem with punnet squares.

Answer 4

Eye color genotypes/phenotypes:

-Your dad: bb (blue blue) / blue

-Your mom: Bb (Brown blue) / Brown

-Your sister: Bb / Brown

-You: bb / blue

Hair color:

I don't think hair color is as simple as eye color.  You say you have auburn hair, which suggests you have a gene for brown hair as well as one for red hair, but supposedly, there is more to hair color inheritance than 1 gene pair.  Just look at the picture and caption in this article:

http://www.thetech.org/genetics/ask.php?...