The presence of the dominant allele masks the appearance of the recessive.

Thus, the phenotypes of the the heterozygote (Aa) and the dominant homozygote (AA) are indistinguishable.

Example: Mendel's peas

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1. Incomplete Dominance
2. Multiple Alleles
3. Epistasis
4. Pleiotropy
5. Polygenic Inheritance

Neither allele is completely dominant, and the F₁ hybrids have a phenotype somewhere between those of the two parental varieties.

Example: Snapdragons

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Phenotypic Ratio: 1 red:2 pink:1 white

NO! The blending theory implies that the original traits (red and white) could never be retrieved from the pink hybrids, which is incorrect.

The segregation of the red-flower and the white-flower alleles in the gametes produced for flower color are heritable factors that maintain their identity in the hybrids (as seen in the incomplete dominance card).

2 pinks produce the 1 RED:2 pink:1 WHITE ratio.

Blood type. ABO blood groups in humans are determined by three alleles on a single gene.

There are four blood types (A, B, O, AB), but there are still three alleles (A, B, O).

O

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Gene at one locus alters expression of gene at another locus

Example: The dogs!

The E/e gene is epistatic to the B/b gene. 

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B=Black

b=brown

E=Expression of other gene at other locus

ee= Stops/halts expression

Notice all the ones with "ee" are albino. 

One gene/many phenotypes

Pleiotropic alleles are responsible for the multiple symptoms associated with certain hereditary diseases, such as cystic fibrosis and sickle-cell disease.

Example: Hemoglobin and sickle cell disease

This is the additive effect of two or more genes on a single phenotypic character, or one gene with multiple phenotypes. (Many genes/one phenotype)

Example: Skin tone

(Regarding skin tone, you can't say someone's skin tone is either _____ or _____; skin tone varies in gradations allong a continuum).

Also, A, B, and C genes in various genotypic combinations lead to different skin tones.

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Pleiotropy.

(Since pleiotropy is one gene/multiple phenotypes and polygenic inheritance is many genes/one phenotype).

Factors unrelated to inheritance.

The outcome of genotype lies within a phenotypic range that depends on the environment in which the genotype is expressed.

For example, hydrangea flowers of the same genetic variety range in color from blue-violet to pink, whith the sade and intensity of color depending on the acidity and aluminum content in the soil (so solely environmental stuff).

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These are used for determining possible offspring based on family history. 

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Usually goes eldest child to youngest child from left to right.

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1. Amniocentisis
2. Chorionic villus sampling (CVS)

If Hb^A is a normal allele and Hb^s is a Sickle cell/mutant allele, how many possible phenotypes are there?

What are they?

The number of phenotypes indicates that the gene for hemoglobin is ______________.

3.

Hb^AHb^A - You're have normal hemoglobin

Hb^AHb^S - You're a carrier for sickle cell anemia

Hb^SHb^S - You have sickle cell anemia/mutant hemoglobin protein

Pleiotropic.