Special Types of Genetics Problems

 

Codominance-two dominant alleles are present

 

Ex.  White fur and black fur are codominant

                White=W            Black=B

 

Human Blood Types-There are three alleles for blood type:  type A (dominant)=A, type B (dominant)=B, and type O (recessive)=o

 

Phenotypes	Genotypes
Type A	AA (homozygous A), Ao (heterozygous A)
Type B	BB (homozygous A), Bo (heterozygous B)
Type AB	AB
Type O	oo

 

Sex-Linked Traits-traits found on sex chromosomes.  Usually found on X chromosomes.  Harmful sex-linked traits are usually recessive.

 

Ex.  Hemophilia is a recessive sex-linked trait.  Normal blood clotting is dominant.

 

Normal clotting =X^N   Hemophilia=Xⁿ     Male=Y