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Dihybrid Crosses and Different Patterns of Inheritance

Dihybrid Crosses and Different Patterns of Inheritance. Dominant/Recessive. when two different alleles are present, one is expressed (dominant) while the other is hidden (recessive). Dihybrid Cross Two Trait Punnett Squares. Dihybrid Cross Two Trait Punnett Squares.

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Dihybrid Crosses and Different Patterns of Inheritance

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  1. Dihybrid Crosses and Different Patterns of Inheritance

  2. Dominant/Recessive • when two different alleles are present, one is expressed (dominant) while the other is hidden (recessive)

  3. Dihybrid CrossTwo Trait Punnett Squares

  4. Dihybrid CrossTwo Trait Punnett Squares • breeding that involves two contrasting traits • Seed Shape: R = round, r = wrinkled • Seed Color: Y = yellow, y = green

  5. Dihybrid CrossTwo Trait Punnett Squares

  6. Dihybrid CrossTwo Trait Punnett Squares

  7. Dihybrid CrossTwo Trait Punnett Squares

  8. Dihybrid Example • A plant that is heterozygous for seed shape (Rr) and heterozygous for seed color (Yy) is self-pollinated. What will the genotypic and phenotypic ratios be of the offspring?

  9. Dihybrid Example

  10. Dihybrid Example

  11. Dihybrid Example

  12. Dihybrid Example • Genotypic Ratio: • 1 RRYY : 2 RRYy : 1 RRyy : 2 RrYY : 4 RrYy : 2 Rryy : 1 rrYY : 2 rrYy : 1 rryy • Phenotypic Ratio: • 9 Round & Yellow : 3 Round & Green : 3 Wrinkled & Yellow : 1 Wrinkled & Green

  13. Sex-linked • a trait that is determined by a gene found on one of the sex chromosomes • many traits are located only on the X chromosome

  14. Sex-linked • leads to many recessive characteristics being common in males • males only have one copy of the X chromosome • Examples in humans • colorblindness (recessive)

  15. Sex-linked • must use sex chromosomes as part of Punnett Squares • Ex: XC = X chromosome with a normal gene, Xc = X chromosome with a colorblind gene, Y = no gene

  16. Incomplete dominance • a condition in which a heterozygous individual appears in-between two different phenotypes • neither allele is competely dominant

  17. Incomplete dominance • two alleles resulting in three phenotypes • heterozygous individuals have a phenotype somewhere in the middle of the two alleles

  18. Incomplete dominance • Example in humans • a straight-haired parent and a curly-haired parent will produce a wavy-haired child • use an apostrophe (’) or superscript letters to indicate different alleles • S = straight, S’ = curly • SS = straight, SS’ = wavy, S’S’ = curly

  19. Incomplete dominance

  20. Codominance • two alleles are expressed at the same time • Example in humans • ABO blood type in humans

  21. Codominance CWCW CRCR CWCR

  22. Codominance • use superscript letters to show different alleles • CW = white, CR = red • CWCW = white, CRCR = red, CWCR = roan

  23. Multiple alleles • genes with 3 or more alleles possible for the same character • Example in humans • ABO blood type in humans

  24. Multiple alleles • use capital and lowercase letters and/or superscript letters to show different alleles • CA = type A blood, CB = type B blood, c = type O blood • CACA = type A blood, CBCB = type B blood, CACB = type AB, cc = type O

  25. Multiple Alleles & Codominance

  26. Polygenic Inheritance • several genes influencing one character • Example in humans: • height, weight, hair color, and skin color • won’t use a Punnett Square with this type of inheritance

  27. Environmental influences • conditions around organisms also influence their phenotype

  28. Environmental influences

  29. Environmental influences

  30. Environmental influences • Examples in humans: • height and weight are influenced by nutrition

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