Review: Grade 11 Genetics

Each person is made up of different traits.  Some people have brown eyes while some have green.  Some people may have blonde hair while others may not.  A child's traits are determined through their parent's genetic makeup.

Alleles are different forms of the same gene or trait.  For the trait of eye colour, there are green eyes, blue eyes, hazel eyes, and brown eyes; all these colours have their own allele.  However, certain traits are dominant over other traits.  For example, brown eyes are dominant to blue eyes.  Therefore, to have brown eyes, an individual would only need one allele for it; whereas with blue eyes, the individual must have both alleles.

We can find the possibly genotype (combination of alleles) and phenotype (physical traits) by using the Punnett Square.  With Gregor Mendel's technique of the Punnett Square, we can find the possible characteristics of two individuals' offspring.

Here are two other forms of inheritance:

Incomplete dominance - A third phenotype is created with one allele affects the second allele.  For example, a  father with straight hair and a mother with curly hair have a daughter with wavy hair.

Codominance - Both phenotypes are expressed when two alleles are equally dominant.  For example, a black cat and a tan cat would make a kitten with black fur and tan fur.