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Mendelian Genetics

Mendelian Genetics. Gregor Mendel. Before Mendel Blended Theory of inheritance Should reach uniform appearance Mendel discovered the particulate theory of inheritance University of Vienna Garden peas. Pea Experiments. Flower color Purple or white Flower position Axial or Terminal

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Gregor Mendel • Before Mendel • Blended Theory of inheritance • Should reach uniform appearance • Mendel discovered the particulate theory of inheritance • University of Vienna • Garden peas

  3. Pea Experiments • Flower color • Purple or white • Flower position • Axial or Terminal • Seed color • Yellow or Green • Seed shape • Wrinkled or round • Pod Shape • Inflated or constricted • Pod Color • Green or yellow • Stem Length • Tall or dwarf

  4. Pea Experiments • Produced True Breeding plant varieties • Always produced same offspring • True breeding parents are called P generation • Hybrid offspring of the P generation is called the F1 • If they are fertilized and produce offspring the offspring are called the F2

  5. Law of Segregation • Two alleles are packed into separate gametes. • Dominance • Recessive • P or p • T or t

  6. Terms • Homozygous • Heterozygous • Phenotype • Genotype • Testcross

  7. Law of Independent Assortment • Each pair of alleles segregates to the gametes independently.

  8. Practice • Monohybrid • Dihybrid • Phenotypic Ratios • Genotypic Ratios

  9. Rules of Probability • Rule of Multiplication • The probability that independent events will occur simultaneously is the product of their individual probabilities. • Question: cross plants that are heterozygous for flower color. What is probability of them being homozygous recessive?

  10. Rules of Probabilty • Answer: • Probability that egg will get a p • ½ • Probabiltity that sperm will get a p • ½ • Answer • ½ x ½ = ¼

  11. Rules of probabiltiy • Dihybrid answer • YyRr x YyRr • Probability of YYRR • Egg have Y and R • ½ x ½ = ¼ • Sperm have Y and R • ½ x ½ = ¼ • ¼ x ¼ = 1/16

  12. Rules of Probabiltity • Rule of Addition • The probabilty of an event that can occur in two or more independent ways is the sum of the separate probabilities of the different ways.

  13. Rules of Probabiltiy • Cross two Heterozygous for flower color. What is the probability that the offspring is heterozygous? • Two ways to be hetero. Either mom give P or p or Dad give P or p • Dom Egg with Rec Sperm • ½ x ½ = 1/4

  14. Rules of Probabiltiy • Dom sperm with rec egg • ½ x ½ = ¼ • Overall ¼ + ¼ = 2/4 = ½

  15. Extending Mendel • Incomplete Dominance • Four O’clock Flowers • Incomplete Dominance vs Codominance • MN blood groups • Dominance doesn’t have to do with which can subdue the other, but rather a phenotypic expression.

  16. Extending Mendel • Multiple Allele Traits • ABO • An individual only gets two out of the possible alleles.

  17. Extending Mendel • Polygenic inheritance • Quantitative characters • Skin color • AABBCC dark • AaBbCc intermediate • aabbcc light

  18. Nature vs. Nurture • Environmental impact on phenotype • Altitude on blood etc… • Behavior • Phenotype integrates the environment and the genotype.

  19. Pedigree • Review various pedigrees to determine • Dominant • Recessive • Consanguinity • Autosomal • Sex linked • Non-nuclear inheritance

  20. Pedigree Symbols

  21. Dominant Pedigree

  22. Recessive Pedigree

  23. X linked Pedigree

  24. X Linked Pedigree

  25. Non-Nuclear

  26. Human genetics • If two people were getting ready to have children but each had a sibling die of a the same recessive disease, what would be the probability of each being a carrier? What about each at the same time?

  27. How do you tell a person carries? • Fetal Testing • Amniocentesis • Chorionic Villus sampling • Ultrasound • Fetoscopy • Newborn screening • PKU

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