Biology 2050 Lect. – Mendel and GeneticsMonohybrid Crosses and part of Dihybrid CrossesMendel was an Augustinian Monk in which experimented with pea plants of various traits and is credited with becoming the founder of modern science of genetics. Character: a heritable feature in which varies among individuals in a species. Example: Flower Color and Height in pea plantsTrait: a variant for a specific trait found within the individuals Example: purple vs white flowers, tall vs short plants True-breeding: the term used to describe a specific individual within Mendel’s studies, it was considered “true breeding” if the individual’s offspring were identical to itself in the instance of self-pollination. Hybridization: the breeding or crossing of two true breeding parents. The different generations within the study were: - The P Generation: Parental Generation, true breeding parents- The F1 Generation: the hybrid offspring of the true breeding parents - The F2 Generation: the offspring produced after the F1 generation self-pollinate or pollinate with others of their generation. Mendel’s Model consists of four related concepts, which are: Alternative versions of genes account for variations in inherited characteristics. Alleles: the alternating forms or versions of a gene For each character, an organism inherits two copies of a gene, on from each parent. When two parents are crossed, the offspring have traits from both individuals.Example: Pea plant 1 is true breeding in purple, another is bred with it that is true bred for white: P Pp Pp Ppp Pp PpIf the two alleles at a locus differ, then one, the dominant allele, determines the organism’s appearance. The other, recessive allele, has no noticeable effect on the organism’s appearance. Example: In Mendel’s experiment, the purple trait was the most promenade trait, and was dominate over the white flowers. Dominate Allele: the trait that is visibly seen in the individual Recessive Allele: the trait that is not as promenade as dominate, however can be seen within individuals within a population in which contain two of these traits. (As seen in the trait chart above) Law of segregation/Independent Assortment: the two alleles for aheritable character segregate during gamete formation (meiosis) and separate. Punnett Square: the chart seen above in which can show possible offspring trait combinations. Homozygous: an organism that has a pair of identical alleles. Heterozygous: an organism that has two different alleles present for a gene. Test Cross: a cross with two dominate individuals, one dominate dominate, and the other dominate recessive Example: Parent 2Parent 1PP = Purple plantpp = white plant As it is seen, the offspring get both alleles, though the offspring are PurpleFur Color in rabbits– Brown = B, white = bB Bb Bb Bbb Bb Bb Phenotype: the trait that is observable Example: Purple vs White Genotype: the genetic makeup of the organism Example: Pp, PP, pp Monohybrid: heterozygous for one particular trait. When these individuals cross with only trait. Dihybrid: a cross between two hybrids with two traits Monohybrid has been the cross that has been used thus far. An example of a dihybrid cross is as follows: A tall, purple flower (PpTT) is crossed with a short, white flower (pptt). PT PT pT pTDepending on what the individual’s gametes are, will determine the traits of the offspring. The individuals within this example are abrown individual, BB, and a white individual, bb. As seen in the Punnett square, the offspring have both traits but brown is the visible one.pt PpTt PpTt ppTt ppTtpt PpTt PpTt ppTt ppTtpt PpTt PpTt ppTt ppTtpt PpTt PpTt ppTt ppTtIndependent assortment example: Tall = T Purple = PShort = t White = pNeed to Memorize: The Most often used phenotypic ratios – monohybrid = 3:1, dihybrid = 9:3:3:1As it can be seen, the multiple traits are a bit confusing, but together, they many form a tall purple individual or tall white one. Chromosomes: Meiosis 2Meiosis 1PPTTMost often used genotypic ratios – monohybrid = 1:2:1, dihybrid =