BIO 171 1st Edition Lecture 5 Outline of Last Lecture I. Meiosis/Multicellularity Cont. II. Mutations *Didn’t get to Mendel’s Laws (will cover in Lecture 5)*Outline of Current Lecture I. Genetic Variation II. Mendel’s Law of Segregation III. Mendel’s Law of Independent Assortment IV. Spectrum of Dominance V. Multiple Alleles VI. Maternal Inheritance Current LectureGenetic Variation -A genotype is the genetic make up of a cell or organism -A phenotype is an organisms observed characteristics oA phenotype results from an interaction between the genotype and the environment-Alleles are the different forms of any gene that correspond to different DNA sequences in the genes (ex= an allele for the gene that determines hair type could be curly or straight)oAn individual who inherits an allele of the same type from each parent is said to be homozygous oAn individual who inherits different types of alleles from each parent is said to be heterozygous -Hybridization is interbreeding between two different varieties or species of an organism (produces offspring) These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-True Breeding is when the physical appearance of the offspring in each successive generation is identical to the previous one (homozygous)-Traits can be dominant or recessive depending on what it is oThe trait that appears in the F1 generation is dominant oThe trait that does not appear is recessive Mendel's Law of Segregation -Allows us to predict genetic outcomes -Each reproductive cell (gamete) can contain only one allele of each gene -Two members of a gene pair segregate equally into gametesoOccurs during anaphase I of meiosis I -A Punnett Square is a way to represent a hybrid cross between two parents to predict the genotypes/phenotypes of their F1 offspring -A test cross is any cross of an unknown genotype with a homozygous recessive genotype (aa)oHelps experimenters to figure out unknown genotype based on the genotypes of the offspring produced -Back cross= mating an F1 offspring with a P1 (parent) organism -Monohybrid cross= one trait; heterozygous parents -Dihybrid cross= two traits; 2 parents heterozygous for both genes oExpected phenotypic ratio is 9:3:3:1-Alleles for different genes segregate independently because of the events that occur in metaphase I, which effects the events that occur in anaphase I-One can also infer the probability that a specific genotype will occur (rather than using a PunnetSquare)oAddition rule= when the possible outcomes being considered cannot occur simultaneously -Mutually exclusive means the probability of either event occurring (sum of individual probabilities)oMultiplication rule= when outcomes can occur simultaneously and the occurrence of one has no effect on the likelihood of the other-Independent is the probability of two individual events occurring together (product of their possibilities) Mendel's Law of Independent Assortment -Independent assortment occurs during metaphase I -Segregation of one set of alleles of a gene pair is independent of the segregation of another set of alleles of a different gene pair oFor some chromosomal pairs, maternal chromosome goes to one pole and paternal goesto the other (during Metaphase I and Anaphase I). For some it is the opposite -Independent assortment results in four possible gametic types that a produced in equal proportions -Genes on the same chromosome that fail to show independent assortment are called linked chromosomes Spectrum of Dominance -= Interaction between alleles of the same gene -Three types of dominance (type of dominance influences the phenotype of a heterozygote):oComplete dominance- phenotype of heterozygote is the same as phenotype of homozygous dominant oIncomplete dominance- phenotype of heterozygote is intermediate to the two homozygotes (unique 3rd phenotype)oCodominance- both alleles are visible in the phenotype of a heterozygote Multiple Alleles -More than two alleles for a gene exist in a population oIn humans, each individual has only 2 alleles for each gene; each gamete (egg and sperm) has only 1 allele for each gene (this is because homologous chromosomes separate in meiosis) Maternal Inheritance-Mitochondria have their own genome, separate from the nucleus o these genes are maternally inherited in humans -Even though both men and women have the ability to inherit these genes, only women can pass these traits on to their