Principles of inheritance & variation II
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The topic discussed here is Monohyrid cross & Dihybrid cross, the Phenotypic ratio & genotypic ratio obtained, test cross
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Principles of inheritance & variation II
- 2. INTRODUCTION
- 3. MENDEL’S EXPERIMENT: MONOHYBRID CROSS
- 6. MONOHYBRID CROSS USING FLOWER COLOUR AS A CHARACTER
- 7. TEST CROSS
- 8. TEST CROSS TO KNOW THE GENOTYPE OF THE PARENT
- 9. TEST CROSS
- 10. FEW EXERCISES PHENOTYPE RED FLOWER WHITE FLOWER GENOTYPE RR X rr GAMETES F1 Rr PHENOTYPE GAMETES F1 SELFED Rr X Rr R r R r R r R r R RR Red Rr Red r Rr Red rr White Phenotypic ratio : 3 red : 1 white 3 : 1 Genotypic ratio : 1 RR : 2 Rr : 1 rr 1 : 2 : 1
- 11. FEW EXERCISES • CROSS BETWEEN • ROUND SEEDS & WRINKLED SEED (ROUND IS DOMINANT OVER WRINKLED) • YELLOW SEEDS X GREEN SEEDS (YELLOW IS DOMINANT OVER GREEN) • AXIAL FLOWER X TERMINAL FLOWER (AXIAL DOMINANT OVER TERMINAL)
- 12. FEW EXERCISES PHENOTYPE ROUNDSEED WRINKLED SEED GENOTYPE RR X rr GAMETES F1 Rr PHENOTYPE round seed GAMETES F1 SELFED Rr X Rr r R r R R r R RR Round Rr Round r Rr round rr Wrinkled Phenotypic ratio : 3 round : 1 wrinkled 3 : 1 Genotypic ratio : 1 : 2: 1
- 13. FEW EXERCISES PHENOTYPE YELLOW SEED GREEN SEED GENOTYPE YY X yy GAMETES F1 Yy PHENOTYPE GAMETES F1 SELFED Yy X Yy y Y y Y Y y Y YY Yellow Yy yellow y Yy yellow yy Green Phenotypic ratio : 3 yellow : 1 green 3 : 1 Genotypic ratio :1 : 2 :1 Y Yy y
- 14. FEW EXERCISES PHENOTYPE AXIAL FLOWER TERMINAL FLOWER GENOTYPE AA X aa GAMETES F1 Aa PHENOTYPE GAMETES F1 SELFED Aa X Aa A a A a A a A AA Axial Aa Axial a Aa Axial aa Terminal Phenotypic ratio : 3 : 1 Genotypic ratio : 1 :2 : 1 A Aa a
- 15. DIHYBRID CROSS
- 16. DIHYBRID CROSSY Y R R y y r r Y R y r Y r y R y r Y R
- 17. DIHYBRID CROSS
- 18. FEW EXERCISES • TALL RED (HOMOZYGOUS DOMINANT] WITH SHORT WHITE [HOMOZYGOUS RECESSIVE] • AXIAL PURPLE (HOMOZYGOUS DOMINANT) WITH TERMINAL WHITE (HOMOZYGOUS RECESSIVE) • TALL WHITE (HOMOZYGOUS) CROSS WITH SHORT RED (HOMOZYGOUS) NOTE: TALL IS DOMINANT OVER SHORT AND RED IS DOMINANT OVER WHITE
- 19. FEW EXERCISES PHENOTYPE TALL RED FLOWER DWARF WHITE FLOWER GENOTYPE TTRR X ttrr GAMETES F1 TtRr PHENOTYPE GAMETES F1 SELFED TtRr X TtRr TR TR tr TR Tr tR tr TR TTRR TTRr TtRR TtRr Tr TTRr TTrr TtRr Ttrr tR TtRR TtRr ttRR ttRr tr TtRr Ttrr ttRr ttrr Phenotypic ratio : 9 tall red : 3 tall white : 3 dwarf red :1 dwarf white 9: 3 : 3 : 1 Tr tR tr
- 20. FEW EXERCISES PHENOTYPE AXIAL PURPLE TERMINAL WHITE GENOTYPE AAPP X aapp GAMETES F1 AaPp PHENOTYPE GAMETES F1 SELFED X AP AP Ap aP ap AP AAPP AAPp AaPP AaPp Ap AAPp AApp AaPp Aapp aP AaPP AaPp aaPP aaPp ap AaPp Aapp aaPp aapp Phenotypic ratio : 9 AXIAL PURPLE : 3 AXIAL WHITE : 3 TERMINAL PURPLE : 1 TERMINAL WHITE 9 : 3 : 3 : 1 ap AP Ap aP ap
- 21. FEW EXERCISES PHENOTYPE TALL WHITE FLOWER SHORT RED FLOWER GENOTYPE TTrr X ttRR GAMETES F1 TtRr PHENOTYPE GAMETES F1 SELFED TtRr X TtRr Tr Phenotypic ratio : 9 : 3 : 3 : 1 Genotypic ratio : TR Tr tR tr TR TTRR TTRr TtRR TtRr Tr TTRr TTrr TtRr TTrr tR TtRR TtRr ttRR ttRr tr TtRr Ttrr ttRr ttrr tR TR Tr tR tr
- 22. MENDEL’S LAW OF INHERITANCE
- 23. MENDEL’S LAW OF INHERITANCE PHENOTYPE ROUND SEED WRINKLED SEED GENOTYPE RR X rr GAMETES F1 Rr PHENOTYPE round seed GAMETES R r rR
- 24. MENDEL’S LAW OF INHERITANCE PHENOTYPE ROUNDSEED WRINKLED SEED GENOTYPE RR X rr GAMETES F1 Rr PHENOTYPE round seed GAMETES R r rR R r
- 25. MENDEL’S LAW OF INHERITANCE Y r y R y r Y R Y R y r Gametes Parent genotype YyRr
- 26. DIHYRBID CROSS BETWEEN HETEROZYGOUS PARENTS PHENOTYPE TALL RED FLOWER SHORT WHITE FLOWER GENOTYPE TtRr X ttrr GAMETES F1 PHENOTYPE GAMETES F1 SELFED TR Tr tr tr TR Tr tR tr tr TtRr Tall Red Ttrr Tall white ttRr Short red ttrr Short white tR
- 27. IMPORTANCE OF MENDELISM • Improvement of plants : Hybridization is used for obtaining improved varieties of plants. This process results in combinations of desirable characters of two or more species or varieties. • Improvement of animals : Mendelism has enabled the plant breeders to improve the races of domestic animals. • Improvement of human race : Laws of heredity postulated by Mendel are equally applicable to mankind. • Disputed parentage : Study of inheritance of the blood group can solve the disputed parentage of a child. • Genetic Counselling : With the knowledge of Mendelism, genetic counsellor can predict the possibility of hereditary defect in early foetus
- 28. REASONS FOR MENDEL’S SUCCESS • His choice of plants as pea plants (Pisum sativum) for his breeding experiments was excellent. • Mendel kept complete record of every cross. • He also used statistical methods and law of probability for finalising his results. • Mendel’s predecessors usually studied many traits simultaneously but he took one or two traits at one time for his experiments. • Mendel was fortunate that the characters which by chance he selected for his experiments did not show linkage, incomplete dominance, gene interaction etc. • He took utmost care to check contamination from foreign pollen at the time of cross breeding. • Mendel formulated theoretical explanations for interpreting his results. He tested his every explanation for its validity. • He did not attempt to solve all the variations reported in his breeding experiments, which were not clear to him, such as linkage.
- 29. THANK YOU