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Monday, April 26, 2010

Gregor Mendel's Punnet Squares

Punnet Square with rabbits

Printable Punnett Worksheet
Printable Introduction, Worksheet, and Quiz
Save to Microsoft word, then open and print worksheet
Save to Microsoft word, then open and print worksheet - a little more difficult.
Example 1

 Example 2
Gregor Mendel first experimented with garden peas, which is a self-pollinating plant.  (The stigma of the flower receives pollen from its own flower.)
"In order to cross-pollinate these plants, Mendel removed the anthers (with pollen). Then, he transferred the pollen from another plant to the stigma of the first plant. He always kept very careful records on these plants.
Mendel noticed that when he allowed pure tall plants to self-pollinate, they always produced pure tall plants. He also noted that dwarf plants which were allowed to self-pollinate produced only dwarf plants. Whenever he crossed a tall plant with a dwarf plant, the first generation was always tall. He said that tallness was a dominant trait and that dwarfness was a recessive trait."  (SOS)
Even though a crossed plant produced a tall plant and looked just like a pure tall plant, it actually was a hybrid.  Two hybrid tall plants will not produce tall plants 100% of the time.
"Genetic Symbols. Inherited traits are controlled by genes. Scientists use letters to represent the genes. Because genes occur in pairs, two letters represent the genes inherited from each parent. A capital letter is used to represent the dominant gene. A small letter is used to represent the recessive gene.
The first letter of the name of a trait is generally used. Mendel's tall peas could be represented by capital T for tall. The dwarf or recessive gene would be little t. Since genes occur in pairs, tall peas could be TT or Tt. TT is purebred for the tall characteristic. Tt is a hybrid for the tall characteristic. Tall plants with TT genes would look exactly like those with Tt, but the recessive gene (t) is hidden. For the plants to be dwarf, both genes must be recessive (tt)." (SOS)
Quotes are from Switched on Schoolhouse, 6th grade lesson "Inheritance."


  1. Ok what if there are two parents and both of these parents have two different dominate genes.

    -Barry. b

    1. A "dominant" gene implies that it would be the only one in any particular genotype. An example would be a parent with the genotype for black hair would apparently have one or both of the dominant black hair genes.

      Here is a post that might help you understand it more.

      As well as some interactive games here:
      Answer questions about genotypes (such as bb, Bb, or B and b, or b and b, etc), and fill in Punnett squares. (Put the male genes at the top of the Punnett square, and the female genes on the left.)


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