Incomplete dominance

Incomplete Dominance

No dominant or recessive traitsTraits are of equal valueAll capital letters are usedExponents or apostrophes are used to signify the presence of genesThree variations are possible

Examples: Snapdragons

True-breeding red = R1R1

True-breeding white = R2R2

Offspring are pink = R1R2

Snapdragon Phenotypes

Sickle Cell Anemia

Genetic disorder causing the red blood cells to be incorrectly shapedNormal shape – disc shaped – round with sunken centerAbnormal shape – crescent or sickle shaped A

’A

Sickle Cell Anemia

Possibilities

AA Normal shaped Red Blood

CellA’A Trait carrierA’A’ Sickle Cell Anemia

Red Blood Cells Video

Function of Red Blood Cells

Normally carries oxygen to cells and exchanges for carbon dioxide Misshapen cells can not carry the needed oxygenMisshaped cells also get stuck in capillaries causing mini blood clots and lack of oxygen to cells

Who is most often affected?

In the U.S. 70,000 people are affectedOne in every 400 African-American newborns has SCAOne in every 10 African Americans has the traitSiciliansMay also be in all ethnic groups

Identification?

Blood test after birth

Complications

Pain/Cramps Sharp and shooting in arms and legs

Strokes/Blood clots Most common in children under 10 Overt stroke before completing high

school causing physical impairment Silent strokes do no cause outward

symptoms but cause difficulty in learning

Fatigue/Lack of oxygen