Can Traits be Inherited Differently?

Not all traits are inherited dominantly or recessively. Some traits will actually show a blending of the characteristics in question. Whereas in dominant traits, one gene is expressed over another (which masks that trait), incompletely dominant traits show a blending of the traits. In this case, all homozygous individuals will show one of the traits, and a heterozygous individual will show a mix of the two traits. The image below depicts snapdragons, a flower whose color is incompletely dominant.

Still other traits are inherited codominantly. In cases of codominant inheritance, neither allele is washed out and both are presented equally. This results in patterns like the flowers depicted below.

A very human example of these two types of inheritance shows up in blood type. The 4 major blood types are A, B, O, and AB. In these cases, blood type O is recessive to both A and B, but A and B are codominant to each other. This can be seen below.

The last major type of inheritance is called Sex linkage. Sex linked genes are genes that appear only on the X or Y chromosome. Because women are XX and men are XY, men will only inherit one gene on the X. If this gene happens to be recessive, then the male will show that characteristic because there is no other dominant gene to wash it out. For this reason, disorders and traits that are recessive X linked traits are more commonly seen in men.

The probability for having a boy or girl can be determined used the X and Y in place of a dominant or recessive gene. This is seen below.

Colorblindness is one such trait that is inherited on the X-chromosome. For this reason, men are far more likely to be colorblind than women. Solving a punnett square using sex linkage can be seen below.