The Basics

Ehhh? Chromosomes?
   Chromosomes are teeny strands of DNA (with some proteins) that carry heriditary information. They are, of course, terribly important to genetics, for obvious reasons. You don't need to completely understand chromosomes to get basic genetics. Just understand that they carry genes (genetic information).

   In humans, females have two X chromosomes, so they are XX. Males have an X and a Y. That is the fundamental difference between men and women. One little chromosome. In birds, it is the opposite. Hens are XY, and cocks are XX. This is important for determining the genetic makeup of the clutch.

Alright, it gets interesting now!
   So now we know that hens are XY and cocks are XX. Each parent contributes one half of the offspring's genes. So, the hen can give an X or a Y, and the cock can give either X. We figure out genetic makeup using something termed a Punnett Square:

   If you've ever studied math indepthly, you may have heard of the FOIL theorem. It stands for First Outside Inside Last. That is exactly  how we are going to fill in the Punnet Square.

   For simplicity's sake, the chromosomes we are messing with will be in RED.

   We take the first chromosome from each parent, and we combine them as below. That makes our first square.
 

   Now, we take the outside chromosome from each parent, and we combine them as below. That makes our second square.

   Does this seem really easy? It is! It's no trick. Next in our FOIL method, we take the inside chromosome from each parent, and we combine them as below. That makes our third square.

   Now we're on to our last step! We take the last chromosome from each parent, and we combine them as below. That makes our fourth square.

   And that's all there is to it! Notice how by doing it this way, we end up with all the cocks on the left side, and all the hens on the right. To make sure you've really mastered the art of Punnett Squares, try crossing this arrangement: AB x CD. I've set it up for you below. Click below to see if you've done it right. If you have, you're ready to go to the next step!