211.1 Mendel’s Insight into Inheritance Patterns Monk in Austria-experimented with pea plants to see how genes are passed on to generation.-found that sperm and egg cells contain genetic information that play a part in the genes of the offspring.Gregor Mendel“Father of Genetics”
3Terms to Know: Gene locus – location of a specific gene Allele – variations of a gene
4Genes Units of information about specific traits. When identical alleles are passed on generation after generation this is called a true-breeding lineage.When offspring inherit a pair of non-identical alleles for a trait this is called a hybrid offspring.
5Homozygous-when both alleles are identical (TT)Heterozygous-when alleles are not identical (Tt)
6Genotype and Phenotype Genotype – genetic makeup of an individual.Phenotype – physical appearance of an individual. Observable traits.
7Tracking Inheritance P = parental generation F1 = first-generation offspringF2 = second-generation offspring
811.2 Mendel’s Theory of Segregation Mendel tested the idea that a plant inherits two units (genes) of information about a trait.He performed a Monohybrid Cross-cross of two parents that are homozygous for different versions of a single trait.F1 offspring will be hybrid, heterozygous.
9Monohybrid Cross P F1 F2 Tall x Dwarf Phenotype DD dd Genotype HomozygousDominantHomozygousRecessiveAll TallClearly Tall is Inherited…What happened to Dwarf?F1DdTall is dominant to tall.HeterozygousF1 x F1 = F2possible gametesPunnett Square:Dd3/4 Tall :1 ratio1/4 DwarfF2DTallDDTallDdpossible gametesdTallDdDwarfddDwarf is not missing…just masked as “recessive” in a diploid state…
11Punnett-square Method If half of a plant’s sperm or eggs were a and half were A, then four outcomes would be possible each time a sperm fertilized an egg.Not precisePossible eventProbable outcomeSperm A meets egg A¼ AA offspringSperm A meets egg a¼ AaSperm a meets egg ASperm a meets egg a¼ aa
12Testcrosses Fertilizing different genotype plants to see results. Test results may reveal whether the organism is homozygous dominant or heterozygous.
13SegregationDiploid cells have pairs of genes, on pairs of homologous chromosomes.The two genes of each pair are separated from each other during meiosis, so they end up in different gametes.They do not effect eachother.
1411.3 Independent Assortment Dihybrid Crosses – crossing two traits.Mendel crosses pea plants with two pairs of genes that were homozygous.9:3:3:1 ratio