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Heredity and Punnett Square
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•   Recap WS 6
•   PowerPoint Slides – Mendel and Punnett
•   Activity 1 – Practice
•   Activity 2 – Consolidate
Recapitulation
• Why do we share common traits with our
  parents?

• Why we share different traits from each
  parent?
  – BUT: Sometimes we don’t share some traits
Mendelian Genetics
Gregor Johann Mendel (1822 – 1884)
• Austrian monk

• Cultivated and studied pea plants in the garden of his
  monastery

• Mendel’s Laws of Inheritance:
   – We inherit one of two forms of a gene from each parent
   – Inheritance of a gene is independent (50-50 chance)

• We inherit two forms of a gene – one from each parent
   Why do we express one form and not the other?
Dominant and Recessive genes
• Dominant gene: the gene that
  masks the other gene and
  expresses itself

• Recessive gene: can only express
  itself when both genes are
  recessive

“How do we find out the
  combinations that are possible?”
                                     LINK
The Punnett square
• Created by Reginald Crundall
  Punnett (1875 – 1967)

• A British geneticist

• How to use a Punnett square?
  – Refer to example
Activity 1 (5 minutes)
• Use the Punnett square to determine the
  different combinations of traits inherited

• What is the probability for each trait?
  – probability and percentage
Activity 2 - Consolidation
Farmer Bob grows two types of corn –
  Purple (dominant) and Yellow
  (recessive).

He would like to grow a new type of corn
  that is 3:1 Purple to Yellow. Which
  corn should he cross?

• Pair up to discuss
• Use the Punnett square to help
  Farmer Bob solve his problem
Activity 2 – EXTENSION (optional)
• How can he know if the Purple or Yellow corn
  he is using is a carrier and not dominant (both
  genes)?

				
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posted:6/24/2012
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