Punnett Squares Notes

Dominance & Punnett Squares

Module 6 | Genetics

​Mendel's Work : Inheritance

• ​Mendel's work was important to understanding inheritance.

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• ​In keeping accurate data, Mendel concluded heredity was related to the principles of probability.

​Mendel & Inheritance

• ​Observe the crosses between two green plants.

• ​We can predict that the offspring will have the following outcomes:

  • ​GG (25%) -- green color

  • ​Gg (50%) -- green color

  • ​gg (25%) -- yellow color

​Punnett Square

​Punnett Square = a chart used to predict the genotype & phenotype of a trait in the offspring of two mates

​Punnett Square Rules

​Large letters are dominant and are written first

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​Small letters are recessive and are written second.

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​If both letters are present, the dominant trait will show in the phenotype.

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​Try not to use letters which look the same in capital and lowercase.

​Punnett Square Terms

​Homozygous Dominant = two large letters for a trait

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​Homozygous Recessive = two small letters for a trait

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​Heterozygous (carrier) = one large letter and one small letter for a trait

​Practice

​In your notes, cross the following:

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​Mother (Ee) x Father (EE)

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​How many would be heterozygous dominant?

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​How many would be homozygous recessive?

Inheritance : Dominance

​There are three (3) types of dominance:

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​Complete Dominance: dominant trait masks the recessive

Inheritance : Dominance

​There are three (3) types of dominance:

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Codominance: both alleles equally show dominance for a trait

Inheritance : Dominance

​There are three (3) types of dominance:

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Incomplete Dominance: both alleles equally show dominance for a trait

Multiple Choice

What type of dominance is shown in the picture?

• Complete dominance

• Incomplete dominance

• Codominance

​Write your summary in your notebook.

​Show it to Mr. Buie to receive credit.