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Genetics and Heredity

Genetics and Heredity. GENETICS. Study of the passing on of characteristics from one organism to its offspring. HEREDITY. The passing of traits from parents to offspring. TRAIT. A characteristic of an organism Examples include: height, skin color, eye color, freckles, nose shape, etc.

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Genetics and Heredity

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  1. Genetics and Heredity

  2. GENETICS • Study of the passing on of characteristics from one organism to its offspring

  3. HEREDITY • The passing of traits from parents to offspring.

  4. TRAIT • A characteristic of an organism • Examples include: height, skin color, eye color, freckles, nose shape, etc. • Traits are controlled by genes.

  5. GENE • The set of information that a controls a trait • It is a segment of DNA on a chromosome • Genes come in 2forms (allele-forms of a gene): a. DOMINANT: allele that will always be expressed (shown) in an offspring • Tries to PREVENT the expression of recessive gene

  6. b. RECESSIVE: allele that will only be expressed if there are no dominant alleles present • Is prevented from showing up if there is a dominant allele present

  7. Example: • Eyecolor- Brown eyes are dominant and blue eyes are recessive. • A person can have a brown allele and a blue allele but still have brown eyes because the brown allele is dominant and hides the blue allele (it’s recessive).

  8. Dominant alleles are represented with a capital letter. • Recessive alleles are represented with a lowercase letter. • R = Dominant • r = recessive • An organism is represented by two letters for each allele (or gene that comes from mom and dad)

  9. Homozygous (purebred)-when a species has two identical (genes)alleles for a trait • Represented by the same 2 letters • Ex. BB (dominant) or bb (recessive) • Heterozygous (hybrid)-when a species has two different (genes) alleles for a trait • Represented by 2 different letters • Ex. Bb

  10. Genotype- genes in an organism that are present • Ex. Bb, bb or BB • Phenotype- an organism’s physical traits (or visible traits) • Ex. Brown eyes, brown hair

  11. MUTATION • Change in a gene’s information (like a change in instructions)

  12. Mutations can be: • HELPFUL • HARMFUL Examples include: Down’s syndrome, color blindness, albinism, sickle cell anemia • NEUTRAL

  13. PUNNET SQUARE • A mathematical model used to predict the chances that offspring will inherit genes from their parents

  14. SAMPLE PUNNET SQUARE

  15. Practice problem #1 • Predict the genotypes for the fur color of the offspring of a brown, heterozygous hamster and a white homozygous hamster. Brown is dominant and white is recessive. • Use any letter you like.

  16. Problem #2 • Predict the gentoypes of the offspring of 2 white homozygous cows. Black is dominant over white. • Use any letter you like.

  17. #2

  18. Problem #3 • Predict the genotypes of the offspring of 2 gray heterozygous rats. Gray is dominant over white, which is recessive. • Use any letter you like.

  19. #3

  20. Practice problem #4 • What are the chances of having a girl or a boy baby? • How would you make a punnett square to show it?

  21. #4

  22. Pedigree Charts • Pedigree: a chart of the genetic history of a family over several generations • They are used to find out the probability of a child having a disorder or a certain trait in a family.

  23. Symbols on a Pedigree Female: Male:

  24. Connecting Pedigree Symbols: • Examples of connected symbols: • Married couple • Children

  25. More symbols in a Ped. Chart:

  26. Example of a ped. Chart: • What does a pedigree chart look like?

  27. Interpreting a Ped. Chart: • 1. Determine if the pedigree chart shows an autosomal or X-linked disease/disorder. • If one sex in the pedigree is affected, it is X-linked. • It is a 50/50 ration between sexes, the the disorder/disease is autosomal. Autosomal doesn’t affect just one sex.

  28. Is it autosomal or X-linked?

  29. Autosomal…why????

  30. Interpreting Ped. Chart cont. • 2. Determine whether the disorder is dominant or recessive. • If it is dominant, one of the parents must have the disorder/trait/disease. • It is is recessive, neither parent has to have the trait/disorder because they can be heterozygous (Bb).

  31. Dominant or Recessive?

  32. Dominant….why????

  33. Dominant or Recessive???

  34. Recessive…..why???

  35. You are researching the inheritance of a red colored tongue in a lizard…. • Is it autosomal or X-linked? • Is it dominant or recessive?

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