Sierpinski’s Triangle

Today, I am going to be talking about Sierpinski's Triangle. Sierpinski's Triangle is a fairly well known fractal: A geometric shape that repeats itself infinitely. Here is a picture of the Triangle:

Recently, in my Honors Biology class, we have been studying genetics. Specifically, Punnett squares in dihybrid and trihybrid crosses. In a dihybrid cross, two characteristics of an organism's phenotype (Physical appearance) are traced through the genotype. Here is an example:

I have highlighted those results that show the dominant phenotype for each trait. As you can see, it looks like a triangle with a blank spot in the middle.
Here is a trihybrid cross, again, with the dominant phenotypes highlighted:

And here is a cross which traces 4 traits:

As you can clearly see, Sierpinski's Triangle has popped up quickly in this sequence.
Another place in biology in which I have found this fractal is in blood types. As you might know, there are quite a few blood types in humans, like A, AB, O, A-, A+, and so on. Only certain blood types are compatible in a transfusion, a transfer of blood between two people. If we arrange the blood type compatibility in a table, we get this:

As you can see, Sierpinski's Triangle has popped up once again.
I am still trying to find the Triangle in Pascal's Triangle, which is a triangle of numbers in which each number is obtained by finding the sum of the two numbers nearest to it on the preceding row.

 Photo Credit: "Sierpinski's Triangle" via Wikimedia Commons, CC.