Why do I have a lot in common with my mother?
In this answer I mainly repeat the comments!

There are several reasons why you might share some traits with your mother.


genetic (see below)
epigenetic
environmental influence while being in the womb
environmental influence up to the time you were 4 years old
the two environment were not so different (maybe because your adoptive parents wanted to follow the will of your mother or just because by chance your adoptive parents have similar behaviour that your mother)
multiple testing issue (see below)


These reasons can be classified into three categories:


environmental variance
genetic variance
poor observation (statistic mistake)


The phenotypic variance in a population is influenced by the environmental variance + the genetic variance + the variance due to the interactions between the environmental and genetic variances. The heritability can be calculated as the part of the phenotypic variance which are genetically determined. Such calculations make sense only for populations not for a given parent-offpsring pair.

genetic: It does not make sense to ask whether the variance of a trait is dominant or recessive. It makes sense to say that "liking pink" is dominant over "liking blue". Therefore, you should tell us what is the variant of a given trait that you share with your mother. In such case we might tell you if this variant is dominant or not over the other variants. But of course, this works only for traits that are at least slightly genetically determined. liking a color will certainly not have a strong genetic variance for example. And even if a trait is 100% genetically determined, complex genetic architecture might make it hard to answer. For example a given variant might be dominant in a given genetic background but recessive in another. Finally, I should say that it costs to perform the necessary study (Genome Wide Association Studies) to know exactly the part of the variance of a given trait that is genetically determined. And of course, such studies depend on the population we look at.

Multiple testing issue: Without realizing, you actually looked at many different traits. You might have looked at your favorite color, your favorite beer, the way you wash your teeth, the sport you practice, the color of room, whether you are calm or impulsive, etc... You might not have paid attention only to things that match but you would have found as many similarities (not the same ones though) with any other human on earth.