Types of Inheritances

Pp 237, 242-245

Single gene traits

• controlled by only one gene

- complete, incomplete, and codominant

EX. Huntington Disease (D/d), Sickle Cell

Anemia (N/S) , Cystic Fibrosis (R/r)

Multiple allele trait• Controlled by more than two alleles in one gene

• Trait controlled by multiple alleles, with two that are codominant and one “null”

IA : produces A antigens on surface of cell IB : produces B antigens i: does not produce antigens

• Still only inherit one copy from each parent for a total of two alleles but have a few to combine

EX. Blood type:

IAIA, IAi , IBIB , IBi , IAIB, ii

Polygenic traits

controlled by additive effects of two or more genes so each gene is responsible for adding

pigment

EX. Skin color (controlled by 3-6 genes), eye

color

Sex linked traits

• Gender determined by XX or XY

• Disorder/trait found on the “X” chromosome

• seen more in men than women

EX. (color blindness and hemophilia)

• “Y” has to come from father

• “XR or Xr” vs just “R or r”

• Possible genotypes and phenotypes:

XR XR = normal vision

XR Xr = normal vision

Xr Xr = color blind

XR Y = normal vision

Xr Y = color blind

XR Xr

XR

Y

XXRRXXrrXXRRXXRR

XXrrYYXXRRYY

Sex-influenced trait

• Usually autosomal

• Specific hormones influence trait/genotype

EX. Baldness: testosterone influences BB