4. Genes and Dominance The F1 generation had the character of only of the parents Mendel drew two conclusions Biological inheritance is determined by factors that are passed from generation to the next The principle of dominance Genes Alleles
6. Genetics and Probability The likelihood that a particular event will occur is called probability The principles of probability can be used to predict the outcomes of genetic crosses
9. The Two Factor Cross: F1 Two different genes passing from generation to another First, Mendel crossed tree-breeding plants (RRYY x rryy) All of the F1 offspring produced the dominant genes
10. The Two Factor Cross: F2 Mendel knew that all the F1 plants were heterozygous for both genes The F2 generation shows how alleles segregate Since the alleles for both genes segregated independently of each other (independent assortment), the ratio was 9:3:3:1 The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes. Independent assortment helps account for the many genetic variations observed in plants, animals, and other organisms
12. Summary of Mendel’s Principles The inheritance of biological characteristics is determined by individual units known as genes. Genes are passed from parents to their offspring In cases in which two or more alleles of the gene for a single trait exist, some forms of the gene may be dominant and others may be recessive In most sexually reproducing organisms, each adult has two copies of each gene - one from each parent. These gens are segregated from each other when gametes are formed The alleles for different genes usually segregate independently of one another
