1 / 86

Unit 4: Cell Division & Heredity

Unit 4: Cell Division & Heredity. Part 3 Ch. 14 & Ch. 15 Mendelian Genetics & Chromosomal Basis of Inheritance. I. Genetics As A Science. Genetics = Study of heredity Heredity = How information gets transferred to us from our parents. II. Genetics Vocabulary.

poppy
Download Presentation

Unit 4: Cell Division & Heredity

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Unit 4: Cell Division & Heredity Part 3 Ch. 14 & Ch. 15 Mendelian Genetics & Chromosomal Basis of Inheritance

  2. I. Genetics As A Science • Genetics = Study of heredity • Heredity = How information gets transferred to us from our parents.

  3. II. Genetics Vocabulary • Trait: Characteristic that is different among individuals. Eye color, height, skin color

  4. II. Genetics Vocabulary • Cross: When 2 individuals mate. 2 trees, 2 dogs, etc.

  5. II. Genetics Vocabulary • Hybrid: Result of crossing individuals with different traits.

  6. III. Discovery of Genetics • Gregor Mendel: Used pea plants to explore heredity.

  7. III. Discovery of Genetics • Mendel concluded 2 things • “Factors” determine what organisms will be like . • Genes – determine traits 1. Height 2. Hair color

  8. III. Discovery of Genetics b. Each “factor” can come in different varieties. 1. Alleles- varieties of genes a. Hair color gene 1. Brown allele 2. Blonde allele 3. Red allele

  9. III. Discovery of Genetics • Mendel concluded 2 things… • Some alleles are “stronger” than others

  10. III. Discovery of Genetics • Law of Dominance: Some alleles are dominant & others are recessive. • Dominant: Will always be seen. • Recessive: Only seen if dominant is not there.

  11. IV. Mendel’s Work • Crossed a tall plant with a short plant. • P Generation = Original pair of plants. (Parents)

  12. IV. Mendel’s Work B. Results • All tall plants F1 = First set of offspring. (children)

  13. IV. Mendel’s Work • Curious about why none were short. 1. Crossed 2 plants from the F1. generation. Yes, mated 2 siblings!

  14. IV. Mendel’s Work D. Results 1. 75% Tall 25% Short F2 = offspring of the F1 generation. (grandchildren)

  15. V. Explaining the Outcomes • The allele for “shortness” didn’t disappear. B. The allele for “tallness” was dominant. How was the recessive allele able to be “recovered”?

  16. V. Explaining the Outcomes • Segregation: Alleles separate from each other during meiosis. • Gametes then combine differently during fertilization. T t T t T t T t T t T t t t T T

  17. VIII. More About Alleles A. Allele combinations 1. Have 2 alleles for each gene Height – Tall or short

  18. VIII. More About Alleles B. Each one represented by the first letter of the dominant allele: • Dominant = Uppercase • Recessive = Lowercase a. Height T = Tall (Dominant) t = Short (Recessive)

  19. VIII. More About Alleles a. If 2 of the SAME allele: HOMOZYGOUS TT = Tall tt = Short HomozygousHomozygous DominantRecessive

  20. VIII. More About Alleles b. If 2 DIFFERENT alleles: HETEROZYGOUS Law of dominance: If dominant is present, it will “cover” the recessive. T t = Tall

  21. IX. Looks Can Be Deceiving! • Phenotype: Physical appearance (What’s on the outside) White, Red • Genotype: Genetic makeup (What’s on the inside) RR, Rr, rr

  22. X. Punnett Squares • Diagrams for predicting results of any cross. Genotype of parent 1 Genotypes of offspring Genotype of parent 2

  23. XI. Single Trait Cross • A cross for 1 trait. 1. Hair color ONLY

  24. XI. Single Trait Cross Genotype of parent 1 T T Genotype of parent 2 t t T T t t

  25. XI. Single Trait Cross Results: All 4 combinations are the same. Results vary depending on parents! T T T t T t t t T t T t

  26. XI. Monohybrid Cross F1 Cross: Cross 2 of the “kids”. Results: 1:2:1 Genotypic Ratio 3:1 Phenotypic Ratio T t TT T t T t T t t t

  27. XI. Monohybrid Cross • RULE: According to the Mendel’s Laws, A monohybrid cross of F1 will ALWAYS result in 3:1 p ratio and 1:2:1 g ratio. • If not… something else is acting. - Alternate types of dominance

  28. XII. Dominant/Recessive?? Simple rules of dominance/recessive don’t always hold true. 1. Incomplete dominance: Both alleles present = Intermediate

  29. XII. Dominant/Recessive?? 2. Codominance: Both alleles present = Both appear Brown & White both dominant = both colors appear

  30. XII. Dominant/Recessive?? 3. Multiple alleles: More than 2 alleles for 1 gene Blood Groups

  31. XII. Dominant/Recessive?? 4. Lethal Dominant Traits Monohybrid cross will yield a 2:1 ratio of dominant to recessive. H.D. not viable so does not count in the total offspring. T t TT T t T t T t t t

  32. Sex Chromosomes 44 Autosomes & 2 Sex chromosomes a. Male: 46,XY b. Female: 46,XX

  33. Sex Chromosomes 3. Sperm = X or Y 4. Egg = X only Female X X XX XX 50% female 50% male X Male XY XY Y

  34. Sex-Linked Genes Found on the sex chromosomes, X or Y. Y-linked traits = “maleness” mostly X-linked traits = many traits - Colorblindness

  35. Sex-Linked Genes Males = Y X All X-linked traits will be expressed in males. Only 1 X chromosome, so either YES or NO! Females = X X If trait is dominant, it will be expressed if 1 copy is present. If trait is recessive, it will be expressed if present on BOTH X chromosomes.

  36. More on X Chromosomes Barr body: One of the X chromosomes in females “turns off” during early development. 2. Only in females; Males need the X!! 3. No baby ever born without an X

  37. XIII. Two Trait Cross • A cross that looks at 2 traits. 1. R = right handed r = left handed 2. D = Dimples d = no dimples

  38. The Testcross • A person has brown hair, and brown hair is dominant. How can we tell the genotype? • Testcross: crossing an unknown genotype with a homozygous recessive. • h.r. will always have KNOWN genotype. • gg jj kk ee

  39. The Testcross • If homozygous dominant: • BB x bb = ALL Bb (all brown hair) • If heterozygous: • Bb x bb = HALF Bb, Half bb (half brown, half blonde)

  40. XII. Dihybrid Cross Genotype of parent 1 = R r D d Genotype of parent 2 = R r D d • Figure out the combinations for each parents’ gametes.

  41. XII. Dihybrid Cross Genotype of parent 1 = R rD d FIRST R r X D d R D

  42. XII. Dihybrid Cross Genotype of parent 1 = R rD d OUTSIDE R r X D d R d

  43. XII. Dihybrid Cross Genotype of parent 1 = R rD d INSIDE R r X D d rD

  44. XII. Dihybrid Cross Genotype of parent 1 = R rD d LAST R r X D d rd

  45. XII. Dihybrid Cross Genotype of parent 1 = R rD d Gamete combinations = R D R d rD rd

  46. XII. Dihybrid Cross Genotype of parent 2 = R rD d Same genotype, same gamete combinations = R D R d rD rd

  47. XII. Dihybrid Cross 2. Make a Punnett square: 16 possibilities

  48. XII. Dihybrid Cross 3. Parents’ possible gametes R D R d r D r d R D R d r D r d

  49. XII. Dihybrid Cross 4. Perform Crosses R D R d r D r d RRDD R D RRDd RrDD RrDd R d RRDd RRdd Rrdd RrDd r D RrDd rrDD rrDd RrDD r d Rrdd rrDd rrdd RrDd

More Related