Genotypes and Phenotypes

1
Genotypes and Phenotypes

• What is a genotype?
• What is a phenotype?
• What is the difference between dominant and
  recessive genes?
• What happens in a cross?

2
Genotypes and Phenotypes

• Phenotype How a gene expresses itself in a
  physical trait.
• For example.
• Tall peas and short peas
• Attached lobes and unattached lobes
• Purple flowers and white flowers

3
Genotypes and Phenotypes

• Genotype Genes responsible for a specific
  trait.
• Different forms of genes that occur on different
  chromosomes are called alleles

4
Genotypes and Phenotypes

• Alleles are either dominant or recessive
• Dominant means the trait cancels out other
  traits. Shown as a capital letter. (T tall
  plant)
• Recessive means the trait is cancelled out.
  Written with a small letter. (t dwarf plant)

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Genotypes and Phenotypes

• A cross of same alleles looks like this

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Genotypes and Phenotypes

• T is a dominant trait (Tall plants)
• t is a recessive trait (dwarf plants)

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Genotypes and Phenotypes

• The offspring all have the same genotypes (Tt)
• The offspring all have the same phenotypes (Tall
  plants)

8
Genotypes and Phenotypes

• A cross of different alleles looks like this

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Genotypes and Phenotypes

• In the offspring there are 3 genotypes (Tt, tt,
  TT)
• In the offspring there are 2 phenotypes (Tall
  plants ¾ dwarf plants ¼ )

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Genotypes and Phenotypes

• For more practice is crosses check out the
  following web site
• http//www.biology.arizona.edu/mendelian_genetics/
  problem_sets/monohybrid_cross/01q.html