9DefinitionsPhenotype - the visible expression of information contained in the genetic make-up of an individualGenotype - the genetic make-up, latent or expressed. The sum of all genes present in an individual.P1 - the parental linesF1 - the first filial generation, the offspring resulting from a cross. F2/ F3 the second and third generations.
10Genetic polymorphisms The stuff of genetic variation 1 locus (monogenic),2 different alleles3 combos possible
11Mendel’s Principles of Inheritance 1) Genetic characteristics are controlled by unit factors (elemente) that exist in pairs in individual organisms.These unit factors represent units of inheritance today called genes.Alternative forms of a single gene are called alleles.Individuals can have identical alleles (homozygous) or different alleles (heterozygous) for a single gene.
14Dominance/Recessiveness When two unlike alleles responsible for a single character are present in a single individual, one is dominant (expressed) to the other which is said to be recessive (silent).XP1+ooGGggF1Gg
15SegregationDuring formation of the gametes, the paired alleles separate or segregate randomly so that each gamete receives either with equal likelihood.Possible sperm allelesGgGGGgGPossibleegg allelesGggggPunnett square
16Sample ProblemFlower position in pea plants is another single gene trait. Axial flower position is dominant to terminal. If we cross a true breeding plant with axial flowers to one with terminal flowers, what phenotypes can we expect in the F1 progeny? in the F2 of a selfing of the F1?
17Sample ProblemHaving dimples is a dominant trait in humans. I have no dimples but my father and mother do. All my siblings have dimples as well. Am I adopted??
21Incomplete (partial) dominance Self F1 pink X pink(R1R2) (R1R2)R R2Possible sperm cellsPossibleegg cellsR1R2R1R2pinkR1R1R2R2Intermediate expression of the phenotype.
22But what about the yellow ? This could be the effect of multiple alleles involved in color production.
23Multiple alleles An example: the ABO blood types in humans Genotype PhenotypeIAIAIAIOIBIBIBIOIAIBIOIOABABO
24Sample problemRed-green color blindness is a sex linked, recessive allele of a single gene trait. My brother-in-law is red-green color blind. My sister is not, but my father might have been. My sister and her husband have 4 sons. My mother (their grandmother) was worried that they would be color blind. Should she have been concerned?
25Genes can be Pleiotropic single gene, multiple effectsex. dwarf
30Each gamete contains only one member of each homologous pair. MeiosisThere are 2 steps of meiosis - 2 cell divisions,but only1 replication of chromosomes.Each gamete contains only one member of each homologous pair.
31Summary Mendel’s “rules of the game” 1) Genes occur in pairs - Genetic characteristics are controlled by genes that exist in pairs.2) Dominance/Recessiveness- When two unlike alleles responsible for a single character are present in a single individual, one is dominant (expressed) to the other which is said to be recessive (silent).3) Segregation- during formation of the gametes, the paired unit factors separate or segregate randomly.
32Discovering genes via Mutant analysis Generating mutantsChemical mutagenesis (EMS)base transition, point mutationRadiationdeletionsTransposons/ T-DNA tagsinsertion/deletions (indels)
33And observing segregation ratios Planned crosses and Punnett squares, Pedigree analysisMutant or polymorphism analysisAutosomal dominant/recessiveSex-linked genes