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Pedigrees and Human Inheritance

Pedigrees and Human Inheritance. SBI3U. Pedigrees. Family trees used by scientists to track the inheritance of certain traits Useful for determining whether a trait is autosomal or sex-linked Symbols Used :. Affected. Unaffected. Mating. Siblings. Male. Female. Sex unspecified.

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Pedigrees and Human Inheritance

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  1. Pedigrees and Human Inheritance SBI3U

  2. Pedigrees • Family trees used by scientists to track the inheritance of certain traits • Useful for determining whether a trait is autosomal or sex-linked • Symbols Used: Affected Unaffected Mating Siblings Male Female Sex unspecified

  3. Pedigrees • The following is an example of a pedigree where some members of the family display an autosomal dominant trait • Determine the genotypes using logic • Roman numeral refers to the generation • Number refers to the individual in the generation I – 1 = GR___ I – 1 = GRGr I I – 2 = GrGr 1 2 II – 1 = GrGr II II – 2 = GR___ II – 2 = GRGr 1 2 3 II – 3 = GrGr

  4. Autosomal Inheritance • Autosomal Dominant • Can tell if a trait is autosomal dominant if: • Both parents are affected by the trait but they have a child who isn’t I 1 2 II 1 2 3

  5. Autosomal Inheritance • Autosomal Recessive • Can tell if a trait is autosomal recessive if: • Both parents are unaffected by the trait but they have a child who is I 1 2 II 1 2 3

  6. Albinism • Determine whether or not albinism is autosomal dominant or recessive • Determine the genotypes of all individuals PNPa PNPa PNPa PNPa I 1 2 3 4 II 1 2 3 4 5 6 PN? PN? PaPa PaPa PaPa PN? III 1 2 3 PNPa PNPa PNPa

  7. Sex-Linked Traits • Some traits are coded for on the X or Y chromosomes • This leads to some interesting heredity • X – linked: coded for on the x-chromosome • Red – Green colour blindness and male-pattern baldness • X – linked traits are disproportionately displayed in males • Y – linked: coded for on the y-chromosome • Reduced fertility • Fewer traits are y-linked since y contains fewer genes than x

  8. Sex-Linked Traits • X – linked recessive • Traits passed down from mothers, most frequently to their sons • Many more males will display the phenotype than females I 1 2 3 4 II 1 2 3 4 5 6 III 1 2 3

  9. Sex-Linked Traits • Y – linked recessive • Traits passed down from fathers to sons. No females will be affected I 1 2 3 4 II 1 2 3 4 5 6 III 1 2 3

  10. Hemophilia in the Royal Family Hemophilia is a sex-linked trait where the affected individual has difficulty forming blood clots

  11. Hemophilia in the Royal Family Hemophilia is a sex-linked trait where the affected individual has difficulty forming blood clots XY XhX I XhX II XhX XY XY XhY X_ III XY XhY XhY XhY IV XY XhY

  12. Homework Pg 201 #1-5

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