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Genetics

Genetics. Intermediate Traits. Traits. Most traits are controlled by more than 1 gene Most traits have multiple alleles. Incomplete dominance. For some traits, neither allele is dominant Blending occurs Ex. Snapdragons

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Genetics

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  1. Genetics Intermediate Traits

  2. Traits • Most traits are controlled by more than 1 gene • Most traits have multiple alleles

  3. Incomplete dominance • For some traits, neither allele is dominant • Blending occurs • Ex. Snapdragons • Cross a red flower with a white flower and get pink flowered offspring

  4. Problem • A true breeding red snapdragon is crossbred with a true breeding white snapdragon. Red and white colors are considered to be incompletely dominant. What will the phenotypic ratio of their offspring be?

  5. Codominance • Both alleles are expressed in the same organism • Ex. Chicken feathers • Black feathered rooster + a white feathered hen = offspring with some white feathers and some black feathers

  6. Problem • In a certain type of rabbit, black fur is codominant with brown fur resulting in an agouti color. If a true breeding black fur rabbit and an agouti rabbit are bred, what will the phenotypic ratio of the offspring be?

  7. Multple Alleles • Each organism has only 2 possible alleles for a trait • Multiple alleles for the trait may exist in the entire population • Ex. Human Blood types • A, B, AB, O

  8. Blood Types • A and B are CODOMINANT • A and B are DOMINANT over O • Written as IA, IB, and I • IA IA produce A blood type • IAi produce A blood type • IBIB produce B blood type • IBi produce B blood type • ii proudces O blood type What type of parents can produce offspring with any blood type?

  9. Problem • A man with type O blood marries a woman with type A blood. They have a son with type O blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

  10. Problem • A man with type O blood marries a woman with type A blood. They have a son with type B blood. Several years later they get a divorce and the wife is suing the husband for child support. Is it possible that he should have to pay?

  11. Polygenetic Traits • Some traits are controlled by more than one gene • Ex. In humans • Height • Eye color • Skin color

  12. Intermediate Patterns of Inheritance

  13. Chromosomes • 2 types • Autosomes are any type of chromosome other than a sex chromosome • Sex chromosomes are X and Y • Females XX – always donate an X • Males XY – determines gender of offspring

  14. Sex – Linked Traits • Determined by alleles located on the sex chromosomes (X and Y chromosomes) • Males have 1 X chromosome meaning they are more likely to show a sex linked recessive trait • Ex. Albinism, hemophilia, blindness, muscular dystrophy are sex linked

  15. Karyotypes • Visual display of all the chromosomes in an organism • Indicate chromosomal abnormalities • Broken, missing, or extra • Down’s syndrome

  16. Down’s syndrome • Results from an extra 21st chromosome

  17. Turner’s syndrome • Only 1 X chromosome and no Y • Always Female • Usually develop normally but may result in shorter stature

  18. Triple X • Goes undiagnosed most of the time • Estimated 1 out of 10 girls are XXX

  19. XYY syndrome • Extra Y chromosome • Only in Males

  20. Klinefelter syndrome • Males • Tendency to develop female-like characteristics

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