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Genes&Society_1 Colour slide perpage_Lecture2

Genotype every person has two copies of every gene on

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Unformatted text preview: rozygous allele; recessive trait) and never in a heterozygous genotype. genotype. Every person has two copies of every gene on autosomal (non-sex determining) chromosomes, one from mother and sex determining) chromosomes one from mother and one one from father. If a genetic trait is recessive, a person needs to inherit two copies of the gene for the trait to be expressed Thus both parents have to be carriers of expressed. Thus, both parents have to be carriers of a recessive recessive trait in order for the offspring to express that trait. If both parents are carriers, there is a 25% chance with each offspring to show the recessive trait each offspring to show the recessive trait. 15 Modification Modification to Mendelian Ratios homozygous parent X homozygous parent Incomplete dominance: F1 offspring heterozygous for for flower color One allele of a pair is not fully dominant over its partner, so the phenotype of the heterozygote is somewhere in between the phenotypes of the two parents. F2 offspring 3 phenotypes in 1:2:1 ratio 16 See IVLE animation Multiple Multiple Alleles ABO Blood Group Inheritance (A and B are Codominance; O is recessive) Codominance; Genotype Protein Phenotype AA A Full effect of A AO AO A Full effect of A BB B Full effect of B BO B Full effect of B AB A, B Full effect of AB OO Neither (no protein) O (no effect) Important for blood Important for blood transfusion transfusion and organ transplantation See IVLE animation and 17 Learn Genetics> Heredity & Traits>Genes & Blood Type Mechanisms of dominance Mechanisms • The states of complete dominance and incomplete dominance result not from genetics, but from biochemistry. • The “completeness” of dominance depends only on how effective the protein is at doing its job. • Incomplete dominance simply means that half as many molecules (in the heterozygote) are not as effective as the number produced by the homozygote. This result in the display of intermediate, blended phenotype of the alleles with degree of color shades or severity in the het...
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