8.2- Hereditary Terminology

Genotype:

• genetic component of inheritance.

• Includes one allele copy from each parent (e.g. BB, Bb, or bb).

Phenotype:

• the physical trait displayed, arising from the genotype (e.g. eye color). 

Dominant alleles:

traits expressed regardless of what the second allele is. Represented as an uppercase letter (e.g. B).

Recessive alleles:

traits only expressed in the presence of another recessive allele. Represented as a lowercase (e.g. b). 

Homozygous:

same allele type from both parents (e.g. BB, bb).

Homozygous Dominant:

two dominant alleles (BB), dominant trait expressed.

Homozygous Recessive:

two recessive alleles (bb), recessive trait expressed. •

Heterozygous:

one dominant allele and one recessive allele (e.g. Bb), dominant trait expressed.

Hemizygous:

have only one allele (gene copy) instead of two. Usually only seen in males due to having only one of each sex chromosome.