Answer:
every thing has two allele traits, if you are dominant or recessive for a trait is determined by your alleles. there are two types of alleles, dominant and recessive. The trait in an organism is determined by the organism's parents. To find whether the organism, in this case a person, has a dominant or recessive trait you can use a punnent square. In science, a dominant trait is indicated by a capital letter (A) and a recessive trait is a lowercase letter (a).
Now, if one parent is homozygous, the two traits the parent has is the same, thus the prefix, homo. homozygous dominant (A,A) homozygous recessive (a,a). But that parent can be heterozygous, or having a dominant and recessive trait (A,a) a dominant trait will ALWAYS over shadow a recessive trait, so if you have one dominant allele, you are dominant for that trait. Now using a punnent square:
Parent one: Homozygous recessive (a,a)
Parent two: Heterozygous (A,a)
punnent square
a a
A A,a A,a
a a,a a,a
the chance of the offspring being dominant for this trait is 50% and the chance of the offspring having a recessive trait 50%
thus you only need one dominant allele for this trait to be expresses