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Genetics: Part III Extending Mendel

Genetics: Part III Extending Mendel. Figure 14.8. EXPERIMENT. YYRR. yyrr. P Generation. Gametes. yr. YR. F 1 Generation. YyRr. Hypothesis of dependent assortment. Predictions. Hypothesis of independent assortment. Sperm. or. Predicted offspring of F 2 generation. 1 / 4. 1 / 4.

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Genetics: Part III Extending Mendel

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  1. Genetics: Part III Extending Mendel

  2. Figure 14.8 EXPERIMENT YYRR yyrr P Generation Gametes yr YR F1 Generation YyRr Hypothesis ofdependent assortment Predictions Hypothesis ofindependent assortment Sperm or Predictedoffspring ofF2 generation 1/4 1/4 1/4 1/4 yR yr Yr YR Sperm 1/2 YR 1/2 yr 1/4 YR YYRR YYRr YyRR YyRr 1/2 YR YyRr YYRR 1/4 Yr Eggs YYRr YYrr Yyrr YyRr Eggs 1/2 yr YyRr yyrr 1/4 yR YyRr yyRr YyRR yyRR 3/4 1/4 yr 1/4 Phenotypic ratio 3:1 Yyrr yyRr YyRr yyrr 3/16 3/16 1/16 9/16 Phenotypic ratio 9:3:3:1 RESULTS 108 101 315 Phenotypic ratio approximately 9:3:3:1 32

  3. Which of these genes are most likely tosegregate as a unit?

  4. Which of these genes are most likely tosegregate as a unit?

  5. Curriculum Framework 3.A.3.b.2 Genes that are adjacent and close to each other on the same chromosome tend to move as a unit; the probability that they will segregate as a unit is a function of the distance between them.

  6. In Drosophila….. Traits for wings, leg length, and eye color are carried on the same chromosome. These genes are linked together on the same chromosome and will sort into the same gamete.

  7. Crossover Value

  8. Calculating Crossover expected unexpected

  9. Extending MendelianGeneticsfor a Single Gene • Inheritance of characters by a single gene may deviate from simple Mendelian patterns in the following situations: • When alleles are not completely dominant or recessive • When a gene has more than two alleles • When a gene produces multiple phenotypes

  10. Degrees of Dominance • Complete dominance occurs when phenotypes of the heterozygote and dominant homozygote are identical • In incomplete dominance, the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties • In codominance, two dominant alleles affect the phenotype in separate, distinguishable ways

  11. Figure 14.10-1 P Generation White Red CWCW CRCR Gametes CW CR

  12. Figure 14.10-2 P Generation White Red CWCW CRCR Gametes CW CR F1 Generation Pink CRCW 1/2 1/2 CR Gametes CW

  13. Figure 14.10-3 P Generation White Red CWCW CRCR Gametes CW CR F1 Generation Pink CRCW 1/2 1/2 CR CW Gametes Sperm F2 Generation 1/2 1/2 CW CR 1/2 CR CRCR CRCW Eggs 1/2 CW CRCW CWCW

  14. Multiple Alleles

  15. Figure 14.11 (a) The three alleles for the ABO blood groups and their carbohydrates Allele IA IB i none Carbohydrate B A (b) Blood group genotypes and phenotypes Genotype ii IAIA or IAi IBIB or IBi IAIB Red blood cellappearance Phenotype(blood group) A AB O B

  16. Key to blood type genotypes

  17. Solve It Sara, who is type O, claims that Ira is the father of her baby. The baby has type O blood. Ira is blood type B. Is it possible that Ira is the father?

  18. Solve It

  19. Curriculum Framework • 3.A.4: The inheritance pattern of many traits cannot be explained by simple Mendelian genetics. • Many traits are the product of multiple genes and/or physiological processes. 1. Patterns of inheritance of many traits do not follow ratios predicted by Mendel’s laws and can be identified by quantitative analysis, where observed phenotypic ratios statistically differ from the predicted ratios.

  20. Polygenic Inheritance

  21. Figure 14.13 AaBbCc AaBbCc Sperm 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 1/8 Eggs 1/8 1/8 1/8 1/8 Phenotypes: 1/64 6/64 15/64 20/64 6/64 1/64 15/64 Number ofdark-skin alleles: 1 2 3 4 5 0 6

  22. Influence of Environment

  23. Created by: Debra Richards Coordinator of K-12 Science Programs Bryan ISD Bryan, TX

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