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Have red eyes a mutant recessive allele of a gene on

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Unformatted text preview: essive allele of a gene on the X mutant chromosome can cause white eyes chromosome Possible combinations of genotype and phenotype: XRXR XRXr XrXr XR Y XrY Genotype Homozygous Dominant Heterozygous Homozygous Recessive Monozygous Dominant Monozygous Recessive Phenotype Female Red-eyed Female Red-eyed Female White-eyed Male Red-eyed Male White-eyed X-Linked Inheritance 8 Human X-Linked Disorders: Red-Green Color Blindness 9 Chromosomal Inherit Color vision In humans: Depends three different classes of cone cells Depends in the retina in Only one type of pigment is present in each Only class of cone cell class ­ The gene for blue-sensitive is autosomal ­ The red-sensitive and green-sensitive genes are The on the X chromosome on ­ Mutations in X-linked genes cause RG color Mutations blindness: blindness: All males with mutation (XbY) are colorblind Only homozygous mutant females (XbXb) are are colorblind colorblind Heterozygous females (XBXb) are asymptomatic are carriers carriers Red-Green Colorblindness Chart 10 X-Linked Recessive Pedigree 11 Human X-Linked Disorders: Muscular Dystrophy 12 Chromosomal Inherit Muscle cells operate by release and rapid Muscle sequestering of calcium sequestering Protein dystrophin required to keep calcium Protein sequestered sequestered Dystrophin production depends on X-linked gene A defective allele (when unopposed) causes absence defective of dystrophin of Allows calcium to leak into muscle cells Causes muscular dystrophy All sufferers male Defective gene always unopposed in males Males die before fathering potentially homozygous Males recessive daughters recessive Human X-Linked Disorders: Hemophilia “Bleeder’s Disease” 13 Chromosomal Inherit Blood of affected person either refuses to clot Blood or clots too slowly or Hemophilia A – due to lack of clotting factor IX Hemophilia B – due to lack of clotting factor Hemophilia VIII VIII Most victims male, receiving the defective Most allele from carrier mother allele Bleed to death from simple bruises, etc. Factor VIII now available via biotechnolo...
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