1 / 23

G e n e t i c s N e w s

G e n e t i c s N e w s. Exam I Returned Monday (?) Our responses on web Thanks for YOUR responses Weekend help Sun 4:30 (S-111) Sun 8:00 (E-107) Summary for Exam II Lab Figure out dilutions. Topics for Today. Terminology. Not today. Quick review. Monohybrid cross. LOTS.

inez-robles
Télécharger la présentation

G e n e t i c s N e w s

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. GeneticsNews • Exam I • Returned Monday (?) • Our responses on web • Thanks for YOUR responses • Weekend help • Sun 4:30 (S-111) • Sun 8:00 (E-107) • Summary for Exam II • Lab • Figure out dilutions

  2. Topics for Today Terminology Not today Quick review Monohybrid cross LOTS Chi2 test

  3. Monohybrid Cross ...GGACCGAT… …CCTGGCTA... ...GGATCGAT… …CCTAGCTA... Colorless compoundPurple compound Enzyme P

  4. Study Question 7Which is the dominant allele? Heterozygous Pp Homozygous PP Homozygous pp If Pphas P phenotype,... then Pis dominant over p

  5. Parental Cross Meiosis I Meiosis II

  6. Study Question 8 Parental Cross Write down the genotypes of the two F1 parents and the gametes they produce

  7. F1 Cross Meiosis I Study Question 13 Restate the Law of Segregation in the language of chromosomes Law of Segregation: Heterozygotes produce equal numbers of the two alleles Law of Segregation: Each of two homologous chromosomes has an equal chance of arising in a gamete through meiosis.

  8. Are Mendel’s conclusions valid? Mendel observed: Ppx Pp 705 purple + 224 white Mendel concluded: Ppx Pp 3:1 purple:white But 3:1 with 929 flowers is really: ~694 purple + 235 white 705 purple and 224 white is close... Is it close enough?

  9. Where does 2 come from?A million repetitions of Mendel’s experiment Create a million universes -- purple:white on average = 3:1 Result: 705 purple224 white = 929 plants Result: 698 purple231 white = 929 plants Result: 688 purple241 white = 929 plants Result: 710 purple219 white = 929 plants Result: 695 purple234 white = 929 plants Result: 702 purple227 white = 929 plants

  10. Where does 2 come from?A million repetitions of Mendel’s experiment 200,000 repetitions

  11. Where does 2 come from?A million repetitions of Mendel’s experiment 500,000 repetitions

  12. Where does 2 come from?A million repetitions of Mendel’s experiment 1,000,000 repetitions Study Question 15: What’s the most likely result? How often does it occur? Study Question 14: Why is it that the two dotted lines are on opposite sides of the mean?

  13. Deviation from ExpectationTwo example experiments Study Question 17:Why is there shading on both sides of the curve? Study Question 18:The farther away O from E, the smaller/larger the shaded area?

  14. Steps in Performing a Chi2 Test Determine the expected values for the experiment Model: 3 purple : 1 white flowerTotal counted: 929Purple = 75% of 929 = 696.75White = 25% of 929 = 232.25 Calculate the squares of the deviations Chi2 = Sum of (O - E)2 / E Chi2 = (705 - 696.75)2 /696.75 + (224 - 232.25)2 /232.25 ~82 / 700 + ~82 / 230 ~0.09 ~0.3Chi2 = approx 0.39 (actually = 0.37)

  15. Steps in Performing a Chi2 Test Determine the degrees of freedom What was the experiment? - Count 929 flowers a million timesAsk: purple? (if not, then white) Therefore ONE degree of freedom Look up probability for 2 value 2 = 0.30 80% > P > 50%. Call it ~60%

  16. Steps in Performing a Chi2 Test P ~60% Draw a conclusion The result has a 50% chance of being correct The hypothesis has a 50% chance of being correct 60% of the time, Mendel’s result or worse would have arisen by chance if purple:white truly occurs in a 3:1ratio.

  17. Deviation from ExpectationTwo example experiments P = .50 P = ??? Study Question 20:What if Mendel had counted not 929 but 929,000 plants -- what does the curve and shading look like then? (d still = 29)

  18. Study Question 25 Are there as many female as male biology majors?How many degrees of freedom? What’s the experiment?

  19. Study Questions 27 and 28 Does a high P value indicate the hypothesis is correct? Does a low P value indicate the hypothesis is incorrect?

  20. Bag of Marbles 1000’s of marbles!50% red, 50% blue Guaranteed!

  21. Test Claim of 50%:50% Is their claim correct? 47 marbles 53 marbles 100 marbles How to tell how close is close enough? TOTAL

  22. 2 Test of Claim Chi2 = Sum of (O - E)2 / E Chi2 = (53 - 50)2 /50 + (47 - 50)2 /50 9 / 50 + 9/ 50 18/500.36 P = ? P = ~60%

  23. Study Question 26 • Although dwarfism is a rare condition in humans, it is nonetheless not so uncommon to encounter a productive union between two dwarves. Suppose you consider the progeny of many such unions and find that 132 are also dwarves and 60 are of normal stature. Does dwarfism appear to be dominant or recessive? Can progeny be reasonably be described as in 3:1 ratio?

More Related