Alleles segregate during gamete formation, but do they do it independently?

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Alleles segregate during gamete formation, but do
they do it independently?
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Two-factor Cross, F1

• RRYY x rryy
• Round/yellow peas wrinkled/green
• What will offspring look like?
• Gives hybrid plants needed for next cross

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Two-Factor Cross, F2

• RrYy x RrYy

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Independent Assortment

• Genes for different traits can segregate
  independently during the formation of gametes.
• Leads to genetic variation in plants, animals,
  and other organisms.

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Not all genes show simple patterns of dominant
and recessive

• Incomplete dominance
• Codominance
• Multiple alleles
• Polygenic traits
• Sex-linked

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Incomplete Dominance

• One allele NOT dominant over another
• Four oclock plants
• RR x WW
• RW

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Codominance

• Both alleles contribute to the phenotype
• Chicken black feathers codom with white
• Heterozygous erminette (speckled)
• Humans protein controlling cholesterol levels
• Blood type

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Multiple Alleles

• Many genes have more than 2 alleles
• Coat color in rabbits
• Human gene for blood type

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Polygenic Traits

• Traits controlled by two or more genes
• At least three genes involved in reddish-brown
  pigment in eyes of fruit flies
• Different combinations of alleles produce
  different eye colors
• Polygenic traits often show a wide range of
  phenotypes
• Skin color in humans partly because more than
  four different genes probably control this trait

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Sex-linked Genes