PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Copyright © 2009 Pearson Education, Inc.Wednesday, August 28, 2013(50th anniversary of the march on Washington and Martin Luther King’s“I Have a Dream” speech).Top 5 for today:1)Terminology – phenotype, genotype, gene, locus, allele, homozygous, heterozygous, P1, F1, F2, true breeding strains, dominant, recessive2)Mendel’s postulates (random segregation, independent assortment)3)Monohybrid cross (and reciprocal cross)4)Dihybrid cross5)Test crossAdd on today: Fork-line Method or Branch DiagramCopyright © 2009 Pearson Education, Inc.In a cross between a black and a white guinea pig, all members of the F1 generation are black. The F2 generation contains 2 white and 7 black guinea pigs. a)Diagram the cross, showing genotypes and phenotypes.b)What will the offspring be like if two F2 white guinea pigs are mated?c)What possible phenotypes would occur in offspring of two F2 black guinea pigs?Quiz – August 28Copyright © 2009 Pearson Education, Inc.Classic Experiment – Monohybrid CrossStep 1: Cross two individuals that differ for one trait (they must come from true breeding strains)P1 Generation (Parental)Step 2: Examine trait in offspringF1 Generation (First Filial)Step 3: Interbreed (or self fertilize) offspring (F1s)Step 4: Examine trait in these offspring (grandchildren) F2 Generation (Second Filial)Copyright © 2009 Pearson Education, Inc.Figure 3.2Mendel’s observationsF1 generation always resembled one of the parents-The F1 trait called the dominant trait-The trait not found in F1 recessiveAlways 3:1 ratio of dominant:recessive-F1 and F2 patterns similar regardless of parent providing ovum or pollenReciprocal crossCopyright © 2009 Pearson Education, Inc.Mendel’s explanation in three postulates:Unit Factors in PairsGenetic characteristics are controlled by unit factors that exist in pairs in individual organisms.Dominance/RecessiveWhen two unlike unit factors responsible for a single characteristic are present in an individual, one factor is dominant to the other, which is said to be recessiveSegregationDuring formation of gametes, the paired unit factors separate (or randomly segregate) so that each gamete receives one or the other with equal likelihood. The paired condition is restored during the random fusion of gametes during fertilization.Copyright © 2009 Pearson Education, Inc.Modern Terminology:Genes – Unit factors of heredityAlleles – alternative forms of genesGenotype – the alleles that an individual possessesPhenotype – the observable attribute of an individualLocus – the position of a gene on a chromosomeHomozygous – the genotype or characteristic of having two identical alleles for a given geneHomozygote – an individual with a homozygous genotypeHeterozygous – the characteristic of having different alleles of a given geneHeterozygote – an individual with a heterozygous genotypeCopyright © 2009 Pearson Education, Inc.Figure 3.3Law of Segregation shown by Punnett square…Punnett square – a way to anticipate the phenotypic and genotypic results of a cross Probability of getting a particular result because of random segregationCopyright © 2009 Pearson Education, Inc.Figure 3.4Copyright © 2009 Pearson Education, Inc.Dihybrid CrossStep 1: Mate individuals that differ for two traits (true breeding strains, P1 generation)Step 2: Examine traits in offspring (F1 generation)Step 3: Self fertilize or interbreed F1 generationStep 4: Examine the traits in these offspring (F2 generation)Practice Problem: Pea seeds can be yellow (dominant) or green (recessive) and they can be round (dom) or wrinkled (rec). Cross a true breeding yellow round pea with a true breeding green wrinkled. Diagram cross and determine phenotypic ratios.Copyright © 2009 Pearson Education, Inc.Figure 3.5Copyright © 2009 Pearson Education, Inc.Mendel’s Fourth PostulateIndependent AssortmentDuring gamete formation the alleles of different genes assort independently of each other A problem for you: In Drosophila, gray body color is dominant to ebony, while long wings are dominant to vestigial wings. Assuming the P1 individuals are homozygous, work the following crosses through the F2 generation, and determine phenotypic ratios for each generation:a)gray, long x ebony, vestigialb)gray, vestigial x ebony, longCopyright © 2009 Pearson Education, Inc.Figure 3.11Copyright © 2009 Pearson Education, Inc.Figure 3.7Copyright © 2009 Pearson Education, Inc.Figure 3.8Copyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc.Figure 3.6Fork-lined or Branch Diagram MethodDihybrid crossGgWw x GgWwAdditional Concepts:Copyright © 2009 Pearson Education, Inc.Figure 3.10Fork-lined or Branch Diagram Method Trihybrid crossAaBbCc x