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Complex Patterns of Inheritance. Unit 4 – Lecture 7. Review . Mendellian / Single-Gene Inheritance two alleles per gene = 1 dominant, 1 recessive ex: R = red, r = blue RR = red Rr = red rr = blue COLOR THE IMAGES ON YOUR LECTURE NOTES. Discuss. What does it mean to be “incomplete” ?

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review
Review
  • Mendellian / Single-Gene Inheritance
    • two alleles per gene = 1 dominant, 1 recessive
    • ex: R = red, r = blue
      • RR = red
      • Rr = red
      • rr = blue
      • COLOR THE IMAGES ON YOUR LECTURE NOTES
discuss
Discuss
  • What does it mean to be “incomplete” ?

[don’t say – to not be complete…think about this]

incomplete dominance
Incomplete Dominance
  • Incomplete Dominance
    • two dominant alleles present
    • BLEND of alleles is expressed when combined
    • uses same letter with “prime” or another letter as exponent
      • can have a recessive allele still – which is hidden by BOTH of the dominant alleles if present.

A 1

incomplete dominance cont d
Incomplete Dominance – cont’d
  • Incomplete Dominance
    • ex: R = red, R1 = blue
      • RR = red
      • RR1 = PURPLE
      • R1R1 = blue
      • COLOR THE IMAGES ON YOUR LECTURE NOTES
codominance
Codominance
  • Codominance
    • two dominant alleles present
    • BOTH alleles are expressed when combined
    • offspring show both phenotypes at same time
    • uses same letter with “prime” or another letter as exponent
      • can have a recessive allele still – which is hidden by BOTH of the dominant alleles if present.
codominance cont d
Codominance – cont’d
  • Codominance
    • ex: R = red, R1 = blue
      • RR = red
      • RR1 = red AND blue[striped, spotted, checkered, etc]
      • R1R1 = blue
      • COLOR THE IMAGES ON YOUR LECTURE NOTES
multiple alleles
Multiple Alleles
  • Multiple Alleles
    • trait is coded for by more than 2 alleles for the SAME gene [same letter!!]
    • more combinations for the same trait
    • gene can have:
      • multiple dominant alleles – like codominant or incomplete dominance
      • multiple recessive alleles – all of which would be hidden by any dominant allele present
ma example discuss
MA Example - Discuss
  • Example: three alleles for the “R” gene
  • R = red R1 = white r = orange
  • What color phenotypes would result from each of the following genotypes? [assume co-dominance]
      • RR RR1
      • R1R1 Rr
      • R1r rr

red

white

white

red AND white

red

orange

multiple alleles cont d
Multiple Alleles – cont’d
  • Multiple Alleles
    • ex: Blood Type – codominant multiple allele trait
      • alleles = IA, IB & io
      • A and B are dominant, O is recessive
      • caps letter “I” lower-case letter “i”
ma discuss
MA – Discuss
  • So…if A [IA] and B [IB] are dominant, and O [io]is recessive …
    • which genotypes will give each blood-type phenotype? [A, B, and O]
    • A blood: IA IA or IA io
    • B blood: IB IB or IB io
    • O blood: only io io
slide12
NOTE
  • You MAY NOT do blood type as your multiple allele trait. Your traits must ALL be able to be seen just by looking at your creature.
polygene inheritance
Polygene Inheritance
  • Polygene Inheritance
    • “poly” = many
    • traits are influenced by many genes
      • will have combinations of different letters
    • ex: traits with ranges or many types
      • hair/eye/skin color, height, build, etc.
polygene inheritance1
Polygene Inheritance
  • Polygene Inheritance
    • ex: A / G / R = red a / g / r = no red
      • more dominant alleles, more color
      • Aa Gg Rr is darker red than Aa gg rr
naming inheritance
Naming Inheritance
  • Types of Chromosomes
    • Autosome = non-sex determining chromosome [1-22]
      • “autosomal” trait = trait on a non-sex chromosome
    • Sex-Chromosome = X or Y, chromosome pair #23
      • “sex-linked” trait = trait on the X or Y [sex] chromosome
naming inheritance1
Naming Inheritance
  • Autosomal Dominant
    • dominant trait on a non-sex chromosome
    • heterozygotes [Aa] and dominant homozygotes [AA] have the trait
    • children with trait have at least one parent with the trait
    • affects males and females equally
naming inheritance2
Naming Inheritance
  • Autosomal Recessive
    • recessive trait on a non-sex chromosome
    • must be recessive homozygote [aa] to have the trait
    • children with trait have parents who either show or carry the trait
      • carrier – heterozygote person for a recessive trait – does not show it, but has the allele [Aa]
      • if both parents have the trait, ALL children will have the trait
naming inheritance3
Naming Inheritance
  • Autosomal Recessive
    • affects males and females equally
    • traits often skip generations
naming inheritance4
Naming Inheritance
  • Sex-linked Dominant [XA]
    • dominant trait on a sex chromosome
    • typically on the X-chromosome
    • many are fatal [especially in males]
    • if both parents have trait, most children will have it
      • ¾ of children if heterozygous mother
      • all children if homozygous mother
    • affects males and females equally
    • if both parents have it, all kids have it.
naming inheritance5
Naming Inheritance
  • Sex-linked Recessive [Xa]
    • recessive trait on a sex-chromosome
    • typically on the X-chromosome
    • females can be carriers; males cannot
    • affects more males than females
      • son with trait can have parents who don’t show trait
      • no father to son transmission of trait
    • traits often skip generations