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December 11 th

December 11 th. Monday. Notebooks Due on Midterm Day. All assignments must be complete No late notebooks will be accepted. Non- mendelian Genetics Incomplete Dominance Codominace Multiple alleles (blood types) Sex-linked Traits. Incomplete Dominance and Codominance.

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December 11 th

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  1. December 11th Monday

  2. Notebooks Due on Midterm Day • All assignments must be complete • No late notebooks will be accepted

  3. Non- mendelian GeneticsIncomplete DominanceCodominaceMultiple alleles (blood types)Sex-linked Traits

  4. Incomplete DominanceandCodominance

  5. Incomplete dominance is when the dominant trait is not completely dominant over the reccessive trait • Heterozygote produces a mix between the two parental types • Snapdragon example: • RR = Red • RW = Pink • WW = White

  6. Incomplete Dominance r r R R • F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. • Example:snapdragons (flower) • red (RR) x white (rr) • RR = red flower • rr = white flower

  7. Incomplete Dominance r produces the F1 generation Rr Rr R R Rr Rr All Rr = pink (heterozygous pink) r

  8. Incomplete Dominance

  9. Codominance occurs if two alleles are dominant and thus both forms of the trait are expressed at the same time. • - Also knowns as multiple alleles • Example: blood type • 1. type A = AA or AO • 2. type B = BB or BO • 3. type AB = AB (both A and B dominate) • 4. type O = OO

  10. Codominance Problem A O AB BO B 2:4 or 50% = AB (type AB) 2:4 or 50% = BO (type B) B AB BO • Example: homozygous male Type B (BB) • x heterozygous female Type A (AO)

  11. Another Codominance Problem A B AO BO O 2:4 or 50% = AO (type A) 2:4 or 50% = BO (type B) O AO BO • Example:male Type O (OO) x female type AB (AB)

  12. Sex-linked Traits • - Traits (genes) located on the sex chromosomes • - Sex chromosomes are X and Y • - XX genotype for females • - XY genotype for males • - Many sex-linked traits are carried on X chromosome only

  13. Sex-linked Traits fruit fly eye color XX chromosome - female Xy chromosome - male Example: Eye color in fruit flies Sex Chromosomes

  14. Sex-linked Trait Problem Xr Xr XR Y • Example: Eye color in fruit flies • (red-eyed male) x (white-eyed female)XRY x XrXr • Remember: the Y chromosome in males does not carry traits. • RR = red eyed • Rr = red eyed • rr = white eyed • XY = male • XX = female

  15. Sex-linked Trait Solution: Xr Xr XR Xr XR Xr XR Y Xr Y Xr Y 50% red eyedfemale (XRXr) 50% white eyed male (XrY)

  16. Female Carriers

  17. Female Carriers • Males only have one X chromosome while females have two X chromosomes • This means females have less of a chance of expressing the sex-linked trait, they are usually carriers of sex-linked traits • Males are more likely to express the sex-linked trait

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