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Mendel and the Gene Idea

Mendel and the Gene Idea. Mendel’s Discoveries Extending Medelian Genetics Mendelian Inheritance in Humans. Mendel’s Discoveries. Experimental and quantitative approach Law of segregation Law of independent assortment Roles of probability Discovered the behavior of genes.

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Mendel and the Gene Idea

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  1. Mendel and the Gene Idea Mendel’s Discoveries Extending Medelian Genetics Mendelian Inheritance in Humans

  2. Mendel’s Discoveries • Experimental and quantitative approach • Law of segregation • Law of independent assortment • Roles of probability • Discovered the behavior of genes

  3. Law of Segregation • Allele pairs segregate during gamete formation and randomly recombine during fertilization • Predicted by Punnett square

  4. Homozygous Heterzygous Phenotype Genotype Monohybrid cross Dihybrid cross Testcross Dominant Recessive P F2 F1 Some useful genetic vocabulary

  5. Law of Independent Assortment • Each pair of alleles segregates independently of other gene pairs during gamete formation

  6. Role of multiplication The probability that two independent events will occur simultaneously is the product of their individual probabilities Role of addition The probability of an event that can occur in two or more independent ways is the sum fo the separate probabilities of of the different ways Roles of Probability

  7. Beyond Mendel • Incomplete dominance • Codominance • Multiple alleles • Pleiotropy • Epistasis • Polygenetic inheritance

  8. What is a dominant allele? • Dominance does NOT determine relative abundance! • Recessive alleles have no message • Recessive product is overwhelmed by product of dominant allele • Recessive product inhibited by dominant product

  9. Mendelian Inheritance in Humans • Difficult to study • Few offspring • Generation-20 yrs • Breeding experiments frowned upon • Understanding comes from family pedigrees

  10. Human Disorders • Recessive lethals • Dominant lethals • Multifactorial disorders

  11. Sickle Cell Disease-Video • http://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.mov

  12. Technology and Genetics • Role of genetic counseling • Carrier recognition • Newborn screening • Fetal testing 1) chorionic villus sampling 2) amniocentesis

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