Genetics

​We use letters to show if the allele is dominant or recessive.

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Dominant alleles only need one to show: AA or Aa

Recessive alleles need two to show: aa​

​Used to predict all possible allele combinations and their frequencies in offspring.

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​Punnett Squares

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​These examples we have just looked at traits that are controlled by only two alleles

• Long tail or short tail

• Tall plant or short plant

• Green or yellow peas in plants

• Red or white flowers

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​Mendelian pattern of inheritance = traits only have two possible alleles with one dominant and one recessive AKA complete dominance

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Non-mendelian inheritance is controlled by multiple alleles​

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Neither allele is dominant.

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The heterozygous genotype will show a third phenotype = blend of the other two​

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​Incomplete Dominance

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Occurs when both alleles are expressed equally

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​Codominance

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​Roaning occurs when the coat of the animal has white hairs and the hairs of any other colored mixed in together.

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Codominance can also create spots/stripes​

Traits that are determined by multiple genes

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Hundreds of genes acan be involved

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​Polygenic Traits

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A single gene affects multiple phenotypes

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Marfan syndrome: genetic disease that affects the development of connective tissue during fetal development, so it has a wide range of effects throughout the body​

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​Elongated arms, legs fingers; joints could be extra flexible; affects eyesight; increases likelihood of cardiovascular issues

​Pleiotropy

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