Below is a Punnett square that shows a model of human inheritance
A
А
Аа
Aa
a
a
Аа
Аа
KEY: A = straight hair (dominant); a = curly hair (recessive)
Which of the following must be true about the parent whose
genes are aa?
a
The parent has straight hair
b The parent is dominant
The parent has curly hair
d The parent is capable of having AA offspring

The parent has curly hair.

Explanation:

If AA is the dominant trait for straight hair and aa is the recessive trait for curly hair, then the parent who has aa genes would be curly haired.

unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.