Variations on Mendelian Genetics Notes
- Phenotype expression is in between dominant and recessive.
- Example: red and white flowered snapdragons crossed to produce pink.
- One allele being expressed isn't enough to produce a red flower.
- Alleles are still there and will be expressed in future crosses.
- Alleles are represented with letter super scripts: CrCr (red), CwCw (white), CrCw (pink).
- Both alleles are fully expressed.
- Example: human blood types. Both A and B blood cell surface proteins expressed.
- Most often seen in biochemical traits.
- Alleles represented with letter super scripts: IAIB.
- More than two alleles are possible for a trait.
- Only two can be present in an individual!
- Different combinations possible though.
- Example alleles: A (IA), B (IB), O (i).
- Genotype examples: A (IAIA or IAi), B (IBIB or IBi), AB (IAIB), O blood (ii).
- Interaction between one or more genes.
- More than one gene affects single phenotypic expression.
- Example: Another gene affects if any pigment is deposited in mammal fur (albinism).
- A single gene affects many phenotypic expressions.
- Some characters exhibit a continuum rather than a discrete trait (red flowers).
- Many genes may be influencing a single phenotypic character.
- Mammal skin and eye color are examples.