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Alternate Patterns of Inheritance

Alternate Patterns of Inheritance. The simple rules of Mendelian inheritance (complete dominanance ) do not always apply…. there are exceptions. 1. Co-Dominance. BOTH alleles are dominant In a heterozygous individual, BOTH are expressed in original form

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Alternate Patterns of Inheritance

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  1. Alternate Patterns of Inheritance

  2. The simple rules of Mendelian inheritance (complete dominanance) do not always apply…. there are exceptions

  3. 1. Co-Dominance • BOTH alleles are dominant • In a heterozygous individual, BOTH are expressed in original form • Results in having characteristics of BOTH parents

  4. Co dominance • Example • Red flowers + white flowers  red/white flowers

  5. Co dominance • Examples in humans: • Blood types • Sickle Cell Anemia

  6. 2. Incomplete Dominance • NEITHER allele is dominant (equal) • In a heterozygous individual NEITHER original trait can be seen • Results in a combined phenotype, or blend

  7. Incomplete dominance • Example • Red flowers + white flowers  pink flowers • Example in humans: Skin color

  8. 3. Sex-linked traits • Sex-linked gene is located on the X chromosome • The X chromosome is longer and has more genes than y • Therefore, sex-linked traits are always x-linked

  9. X-linked traits • Result • Females will have 2 copies of the sex-linked trait • Males only have one copy of this gene • Even if the gene is recessive, males only need one gene to get the trait • Therefore males exhibit some traits more frequently than females

  10. Example of x-linked traits • HEMOPHILIA • Recessive disorder • Missing a trait that codes for a protein essential to blood clotting • Bleeders disease – bleed very easily • Females can get the disease, but usually act as a carrier (have the gene/not the disorder)

  11. PHENOTYPE Normal female Female carrier Hemophiliac female Normal male Hemophiliac male GENOTYPE XX XhX XhXh XY XhY HEMOPHILIA

  12. Other examples of x-linked • BALDNESS • Red/Green Color blindness • Color vision test

  13. 1. dominant 2. recessive 3. genotype 4. phenotype 5. allele 6. homozygous 7.heterozygous 8. incomplete dominance co dominance x-linked traits 11. genotypic ratio 12. phenotypic ratio Genetics Vocabulary

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