Parents pass instructions to their offspring, and the instructions set the offspring's inherited traits.

A parent has many instructions, and it passes only some of them to each young one.

Mom's list of instructions and Dad's list. Each list has many lines.

Ella got some of her mom's instructions and some of her dad's. That is one mix.

Her sister got some of her mom's instructions and some of her dad's too. But her sister got a different mix.

Ella's list and her sister's list, each made from some of Mom's lines and some of Dad's. Both lists say brown eyes; the hair lines differ.

Both mixes say: grow brown eyes. So both sisters have brown eyes.

Ella's mix says: grow dark, curly hair, and her sister's mix says: grow light, straight hair.

So their hair differs.