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Disorders and Other Patterns of Inheritance

Disorders and Other Patterns of Inheritance. Biology 1-2. Inherited Disorders. In humans, many genetic disorders show complete dominance. Recessive disorders are caused by a recessive allele.

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Disorders and Other Patterns of Inheritance

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  1. Disorders and Other Patterns of Inheritance Biology 1-2

  2. Inherited Disorders • In humans, many genetic disorders show complete dominance. • Recessive disorders are caused by a recessive allele. • Heterozygotes are carriers (have the recessive allele and can pass it on but do not show symptoms of the disorder).

  3. Inherited Disorders cont’d • Dominant disorders are caused by a dominant allele. • Both homozygous dominant and heterozygotes show the disorder. • There are no carriers.

  4. Pedigrees • A pedigree is a family tree tracing the history of a trait in a particular family. • Circle = female • Square = male • Shaded= person with the trait. • Unshaded= either does not have the trait or is unknown.

  5. Incomplete Dominance • Incomplete dominance-the heterozygote has an appearance that is an intermediate between the parents. • The heterozygote produces a phenotype that is a blend of the other two phenotypes. • Both alleles are dominant. • Written as capital letters.

  6. Codominance • Codominance-both alleles are expressed fully in the heterozygote. • Both alleles show completely and fully. • The heterozygote has both traits. • Both alleles are dominant. • No recessive alleles. • Both written as capitals.

  7. Sex-Linked Traits • Sex-linked traits are genes carried on the X or Y chromosomes. • Show more frequently in males than females. • Males have a single X chromosome. • Receive one copy of any gene on the X chromosome. • Y chromosome has no equivalent gene. • Males show the gene on the X and cannot hide a recessive.

  8. Sex-Linked cont’d • Females have two Xs • A recessive on one X can be covered by a dominant on the other X. • Are written as XnXn or XnY • n is letter of the trait. • Also includes traits that determine gender.

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