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Mendelian Genetics

Mendelian Genetics. Gregor Mendel The Father of Genetics. Gene. A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses). Alleles. •Alleles are alternate forms of a gene.

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Gregor MendelThe Father of Genetics

  3. Gene • A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA in some viruses)

  4. Alleles • •Alleles are alternate forms of a gene. • •Examples: tall and short for plant height or purple or white for flower color. • •Every trait has at least two alleles- one from each parent. • •The location of an allele on a chromosome is known as its locus (loci = plural form).

  5. Genotype • •The letters that represent (symbolize) the trait being investigated. The genetic make-up of an organism. • •Examples: Bb, BB, bb

  6. Phenotype • The actual representation of the genes. The Physical appearance or traits in an organism resulting from its genetic makeup (what you see). • Examples: tall, purple flower or white flower, blond hair, freckles, etc.

  7. Dominant • The allele that is fully expressed in an organism (observed). • •Represented by capital letters. • •Tall = T

  8. Recessive • •The allele that is masked by the dominant allele. • •Represented by lower case letters. • •Short = t

  9. Homozygous • When both alleles (letters) are the same. • BB = Homozygous Dominant • bb = Homozygous recessive

  10. Heterozygous • When the alleles (letters) are different. • One upper case letter and one that is lower case. • Bb = Heterozygous

  11. Example Problem • Round = R • wrinkled = r • If a plant has round seeds, do we know what its genotype is? • It could be RR or Rr • If a plant has wrinkled seeds, do we know what its genotype is? • Yes, it is rr.

  12. Punnett Square • A method for finding predicted outcomes and probabilities for offspring from any cross. • A chart for predicting the traits of offspring.

  13. Some more terms: • P-generation is the parental generation. • The p-generation produce the F1 generation. • The F1 generation crossed with itself produces the F2 generation.

  14. Example Problem

  15. In foxes, red coat color is determined by the dominant gene R; silver-black coat is determined by the recessive gene r. A homozygous (pure) red male is crossed with a silver-black female. (The P generation). 1.What is the genotype of the female?

  16. What are the genotype percentages of their offspring? •First…make a Punnett square for showing your work

  17. R R Example Problem r Rr Rr r Rr Rr

  18. Assignment • Section 32-3

  19. Assignment 33-4 & 33-5

  20. 1 point B = Brown b = blue B b #1 b Bb bb b bb Bb

  21. 1 point #1 • 1/2 or 50% chance of blue-eyed. • 1/2 or 50% chance of Brown-eyed.

  22. 1 point T = Tall t = short #2 T t t Tt tt t tt Tt

  23. 1 point #2 What fraction of offspring would be tall? • 1/2 or 50% would be Tall.

  24. 1 point W = White w = black #3 W w W WW Ww w ww Ww

  25. 1 point #3a What fraction of the offspring will be white? • 3/4 or 75% will be white.

  26. 1 point #3b What fraction of the offspring will be black? • 1/4 or 25% will be black.

  27. 1 point #3c What fraction of each genotype will you get? • 1/4 or 25% will be WW • 1/2 or 50% will be Ww • 1/4 or 25% will be ww.

  28. 1 point #3d What fraction of each phenotype will you get? • 3/4 or 75% will be White. • 1/4 or 25% will be black.

  29. 1 point RR = Red WW = White RW = Roan #4 R R W RW RW W RW RW

  30. 1 point #4 Give the fraction of each color of offspring? • 1/1 or 100% will be Roan - RW.

  31. 1 point #5 RR = Red WW = White RW = Roan R W W RW WW W WW RW

  32. 1 point #5 Give the fraction of each color of offspring? • 1/2 or 50% will be Roan - RW. • 1/2 or 50% will be White - WW.

  33. 1 point G = Green g = red #1a G g G GG Gg g gg Gg

  34. 1 point #1a Give the fraction of each genotype of offspring? • 1/4 or 25% will be GG. • 1/2 or 50% will be Gg. • 1/4 or 25% will be gg.

  35. 1 point G = Green g = red #1b G g g Gg gg g gg Gg

  36. 1 point #1b Give the fraction of each genotype of offspring? • 1/2 or 50% will be Gg. • 1/2 or 50% will be gg.

  37. 1 point #2a What is the fraction of each phenotype? • 3/4 or 75% will be Green. • 1/4 or 25% will be red.

  38. 1 point #2b What is the fraction of each phenotype. • 1/2 or 50% will be Green • 1/2 or 50% will be red.

  39. b b # 3 B Bb Bb 1 point b bb bb • The mother had to be heterozygous or Bb since the couple had a blue eyed child.

  40. 1 point # 4 • There would be a 50% chance that the 2nd child from the couple would have a brown eyes.

  41. 2 points # 5 The couple had two spotted and two white kittens. • Spotted = S • white = s • Mother = ss since she is white. • Father’s Genotype would be Ss. • Father’s Phenotype would be Spotted

  42. 5 points # 6 • Man has blue eyes - bb. • G-Ma has blue eyes - bb. • Woman has brown eyes - Bb. • 50% of children would be Bb. (Brown) • 50% of children would be bb. (Blue)

  43. Please put a score on top of their paper. • Put the number correct out of 28

  44. Punnett Squares • Why are punnett squares useful? • We can use a punnett square to predict the probable genotypes and phenotypes for offspring from a genetic cross. • Genotype = What is inside the genes, the make-up. • Phenotype = The outward expression of the genes.

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