berit
Uploaded by
38 SLIDES
544 VIEWS
390LIKES

EVIDENCE FROM GENETICS

DESCRIPTION

This comprehensive guide explores monohybrid and dihybrid crosses, key concepts in genetics. By analyzing examples, including crosses between homozygous recessive and heterozygous traits, the material helps clarify dominant and recessive inheritance patterns. Discover the implications of Gregor Mendel's experiments with pea plants, learn to calculate offspring ratios, and delve into the principles of independent assortment. Enhance your understanding of genetic principles while answering interactive questions related to real-world scenarios in inheritance.

1 / 38

Download Presentation

EVIDENCE FROM GENETICS

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. EVIDENCE FROM GENETICS

  2. Can you answer this? Which represents a monohybrid cross between a homozygous recessive and a heterozygote? A) Tt x Tt B) ttmm x TtMm C) tt x Tt D) ttmm x TTMM

  3. Can you answer this? In rats, black fur is dominant over white. If a white rat is crossed with a heterozygous black rat, what is the likely % of the offspring that will be white? • 0% • 25% • 50% • 75%

  4. And can you answer this? Which of the following pairs of crosses results in the same phenotypic ratios? • Aa x Aa and AA x aa • AA x aa and AA x Aa • AA x Aa and Aa x aa • None of the above

  5. EVIDENCE FROM GENETICS • Deduction: If the hypothesis of evolution is correct, then we should see evidence of this in genetics • Background: Gregor Mendel (1822-1884 Experiments with the garden pea. His paper in 1866 established the field of genetics.

  6. MENDEL’S GARDEN

  7. Mendel at work

  8. Mendel at work

  9. Mendel’s Traits

  10. Monohybrid Crosses(=Breeding experiments involving one trait) • Pea plants • P Tall x Tall Short x Short • F1 All Tall All Short

  11. Monohybrid Crosses(=Breeding experiments involving one trait) • Pea plants • P Tall x Tall Short x Short • F1 All Tall All Short • F2 All Tall The tall trait is dominant

  12. Monohybrid Crosses(=Breeding experiments involving one trait) • Pea plants • P Tall x Tall Short x Short • F1 All Tall All Short • F2 F2 x F2 All Tall

  13. Monohybrid Crosses(=Breeding experiments involving one trait) • Pea plants • P Tall x Tall Short x Short • F1 All Tall All Short • F2 F2 x F2 • F3 75% Tall, 25% Short All Tall 3:1 Ratio

  14. 5474/1850= 2.96 6022/2001= 3.01 882/299= 2.95 428/152= 2.82 705/224= 3.15 651/207= 3.14 787/277= 2.84 MENDEL’S TRAITS

  15. 5474/1850= 2.96 6022/2001= 3.01 882/299= 2.95 428/152= 2.82 705/224= 3.15 651/207= 3.14 787/277= 2.84 MENDEL’S TRAITS 3:1 Ratio

  16. Mendel analyzes the data Traits passed in the gametes Pollen (sperm) & eggs Note: ¾ Tall= TT, Tt, tT ¼ Short= tt 3:1 Phenotypic Ratio

  17. Terms and Principles • Dominant (e.g. Tall) • Recessive (e.g. Short) • Phenotype (visible characteristics) • Genotype (genetic characteristics) • Particulate theory of inheritance= 2 particles (factors) determine a trait Blending hypothesis is wrong!

  18. Using a Punnett Square Alleles= Alternative forms of the same gene (T or t) T t T TT Tt t Tt tt Suppose Tt X Tt

  19. Using a Punnett Square Note: 3:1 ratio Eggs T t T TT Tt Pollen t Tt tt Tall Tall Short Tall

  20. Using a Punnett Square Homozygous condition= both alleles are alike (TT or tt) T t T TT Tt t Tt tt

  21. Using a Punnett Square Heterozygous condition= both alleles are different (Tt) T t T TT Tt t Tt tt

  22. Clicker Question • Blue eyes (b) are recessive to brown (B).Suppose 2 parents had 11 children: 6 with blue and 5 with brown. Which of these statements is most likely to be right? • Both parents had blue eyes. • One parent had blue & the other was homozygous dominant • Both parents had brown eyes. • One parent had blue & the other was heterozygous • Both parents were heterozygous.

  23. Dihybrid Crosses(=Breeding experiments involving two traits) Round (R) or Wrinkled (r) seeds Yellow (Y) or Green (y) seeds P RRYY x rryy F1 RrYy Genotype Round Yellow Phenotype

  24. Dihybrid Cross RrYy x RrYy Set up a Punnet Square

  25. Dihybrid Cross RrYy x RrYy

  26. Dihybrid Cross RrYy x RrYy Fill in this line first

  27. Dihybrid CrossRrYy x RrYy Now fill in the rest

  28. Clicker QuestionWhat belongs in the red square? • A) RRYY • B) RrYY • C rrYy • D) rrYY • E) rryy

  29. Dihybrid CrossRrYy x RrYy

  30. Clicker Question:How many wrinkled green seeds will there be out of 16 possibilities? • A) All 16 • B) 9 out of 16 • C) 50% • D) 3 0ut of 16 • E) 1 out of 16

  31. Clicker Question:How many wrinkled green seeds will there be out of 16 possibilities? • A) All 16 • B) 9 out of 16 • C) 50% • D) 3 0ut of 16 • E) 1 out of 16

  32. Dihybrid CrossRrYy x RrYy 9: 3: 3: 1 Round Round Wrinkled Wrinkled Yellow Green Yellow Green

  33. Principle of Independent Assortment = Factors (genes) sort independently of one another. i.e. all possible combinations of Y and y and R and r occur BUT

  34. What ifRY are linked together & ry are linked together ? Non Independent Assortment

  35. Can you answer this? Which represents a monohybrid cross between a homozygous recessive and a heterozygote? A) Tt x Tt B) ttmm x TtMm C) tt x Tt D) ttmm x TTMM

  36. Can you answer this? In rats, black fur is dominant over white. If a white rat is crossed with a heterozygous black rat, what is the likely % of the offspring that will be white? • 0% • 25% • 50% • 75%

  37. And can you answer this? Which of the following pairs of crosses results in the same phenotypic ratios? • Aa x Aa and AA x aa • AA x aa and AA x Aa • AA x Aa and Aa x aa • None of the above

  38. According to J.K. Rowling wizards & witches can be born from pure bloods or muggles. Suppose the wizard/witch trait is recessive (m)and the muggle trait is dominant (M) • Hermione is a witch born of muggle parents. If her parents had another child what are the chances that that one also would be a wizard or witch? • 0% • 25% • 50% • 75% • 100% B E D A C

More Related