COMPLETE DOMINANCE:
Mendel concluded that some alleles are dominant and others are recessive. When one dominant allele is present, it's enough to make the recessive allele unexpressed (this is what happens in heterozygous individuals). In other words, it 'hides' or masks the recessive allele.
CO-DOMINANCE:
-a condition in which both alleles are dominant.
There are alleles that have the capacity of dominating at the same time, and when an organism is heterozygotic, both alleles are expressed.
For example, a white chicken(WW) crossed with a black chicken (BB): 100% of the offspring being WB. With this genotype, they have black feathers and white feathers.
It's not a blend of colors, but a case where both are expressing.
INCOMPLETE DOMINANCE:
-a condition with none of the alleles is dominant or recessive, so the traits blend in the phenotype.
Some alleles are not completely dominant, and when that's the case the phenotype of a heterozygous organism will be a mix between the phenotypes of its homozygous parents.
For example:
plant 1: RR -red
plant 2: rr- white
By crossing this plants we will obtain 100% of the offspring with a color mix: pink.(genotype: Rr)
Red and white are not completely dominating so it results in a blend of colors.
SEX LINKED TRAITS
Sex chromosomes contain genes that determine the sex of a person. Two X chromosomes result in a female and one X plus a Y result in a male.
In those chromosomes, there are genes specific for each gender, and in those chromosomes, there are genes that code for certain traits- the sex-linked traits.
These traits will be inherited according to the sex chromosomes they receive from their parents.