Patterns of Inheritance

1. Polygenic traits -Traits controlled by many genes

ex. Skin color:

• 6 genes control the amount of melanin produced

• more melanin means darker skin color

2. Complex Characters- traits affected by the environment as well as genetics• Exposure to sunlight :

skin color• Nutrition:

Height, Diabetes, Heart disease• Soil type:

Hydrangea flowers are blue if grown in acidic soil

3. Multiple Allele Traits

Ex: Human Blood types

Alleles : A, B, O

4. Sex linked Traits – on the x chromosome

Ex: colorblindnessHemophilia

6. Sex influenced traits-influenced by sex hormones

Ex: baldness – influenced by testosteronedominant in menrecessive in women

7. Incomplete DominanceEx: Sickle Cell Trait

• Point mutation on chromosome 11 causes improperly formed hemoglobin.

• This causes sickle shaped red blood cells which cannot carry oxygen properly and may clog capillaries

Genotype phenotypeSS Normal red blood cells

AA Has sickle cell disease

AS is a carrier of sickle cell, has few symptoms, is resistant to malaria

symptoms

Pain in legs, elsewhereWeaknessFatigue may lead to tissue and organ damage