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Genetic Exceptions

Genetic Exceptions. Incomplete D ominance, and C odominance. Law of Dominance. 1st Law – Law of Dominance – Some alleles will be shown while some other alleles will not be shown. I was wrong??. Incomplete Dominance. Normally if dominant allele is present then its trait will show however...

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Genetic Exceptions

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  1. Genetic Exceptions Incomplete Dominance, and Codominance

  2. Law of Dominance • 1st Law – Law of Dominance – Some alleles will be shown while some other alleles will not be shown. I was wrong??

  3. Incomplete Dominance • Normally if dominant allele is present then its trait will show however... • Sometimes offspring have alleles (2 or more) that influence phenotype. • Phenotype that results is a “blending” of proteins. • Alleles themselves do not combine, only the characteristics they code for.

  4. Example: Flower Color Red (R) Blue (r) R R R r Rr Rr R r Rr RR r Rr rr Rr r Rr All F1= Heterozygous (Rr) F2 = 1 RR : 2 Rr: 1 rr All Heterozygous genotypes will show the blending of phenotypes. NOT MIXING ALLELES, MIXING PROTEINS!

  5. Codominance • Shared dominance. Two dominant alleles code different proteins. • No true dominant alleles. -R’ = represents the codominant allele • No blending of characteristics. -All dominant proteins are coded.

  6. Example 1: Coat color R= brown R’= black R R’ R R’ RR RR’ RR’ R’R’

  7. Example 2: Sickle Cell R= Round R’= Sickle R R’ R R’ RR RR’ RR’ R’R’

  8. Example 3: Blood Types • 3 alleles code for blood type: IA IBand i(type O) • A is codominant with Band both are expressed: Type AB • Ais dominant over O : Type AA or AO • B is dominant to O : Type BB or BO • Ois recessive: Type OO

  9. Pedigrees and Sex-linked traits

  10. Pedigrees A diagram that traces the inheritance of a particular trait through several generations -Normal Male -Normal Female -Male w/ Trait -Female w/ Trait -Male who is a -Female who is a carrier of trait carrier of trait

  11. Roman numerals- Generations - Siblings -Generation I II III

  12. Sex-Linked Trait Traits that are controlled by genes located on the X chromosome Also known as X-linked traits Males are affected more often because they only have one X chromosome.

  13. Females must have it on both X chromosomes to show the trait. Females with only one effected X chromosome are considered carriers EX. Hemophilia

  14. Cross a male without hemophilia with a female who is a carrier • XHY xXHXh • What is the chance of producing a boy baby with hemophilia?

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