Patterns of Gene Expression 1 Dominant 2 Recessive

Patterns of Gene Expression – 1. Dominant – 2. Recessive

3. Codominance – Two different alleles of the same trait are fully expressed – Ex: Human blood types - A, B, AB, O – Alleles: IA, IB, i – IA & IB - codominant – i - recessive (ii=type O blood)

Genotype Phenotype IA IA or IAi IB IB or IBi I A IB ii

Genotypes Surface Proteins Phenotypes IA IA or IAi A A IB IB or IBi B B IA I B A and B AB ii none O

3. Codominance – Use ALL capital letters (no recessive trait except with blood) – EX: When a white cow is crossed with a red cow, a roan cow is produced. Cross a heterozygous cow with a white cow.

• Examples

4. Incomplete Dominance – Two different alleles of same trait combine (BLEND) to form a new expression of alleles – Ex: Colors in flowers, red + white pink

Comparison – Codominance – Incomplete dominance

4. Incomplete Dominance – EX: When a person with straight hair is crossed with a person with curly hair, a wavy haired person is produced. Cross a curly haired person with a wavy haired person.

5. Sex linked traits – Traits carried on the sex chromosomes (mostly the x chromosome)

– Ex. Colorblind, hemophilia Summary – 3 -4 sentences

6. Polygenic traits –Trait produced from many alleles on more than one chromosome –Ex. Hair color, skin color, eye color, height