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

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

Some useful genetic vocabulary Homozygous Heterzygous Phenotype Genotype Monohybrid cross Dihybrid cross Testcross Dominant Recessive P F 2 F 1

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

Roles of Probability 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

Beyond Mendel Incomplete dominance Codominance Multiple alleles Pleiotropy Epistasis Polygenetic inheritance

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

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

Human Disorders Recessive lethals Dominant lethals Multifactorial disorders

Sickle Cell Disease-Video rg/biointeractive/ media/DNAi_sickl ecell-lg.mov rg/biointeractive/ media/DNAi_sickl ecell-lg.mov

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