Presentation on theme: "Why Do You Look Like You Do?"— Presentation transcript:
1 Why Do You Look Like You Do? GeneticsWhy Do You Look Like You Do?
2 What You Should Learn From This Presentation You should know the definition of each of the bold, underlined wordsYou should know the general theme of the presentationWe will go over the presentation as a group, be prepared to discuss it
4 History of Genetics 10,000 years ago, farmers in Egypt bred wheat 4,000 years ago, Asian horse breeders kept records of animal traitsHumans have been controlling the traits of crops and livestock since before the beginning of history
5 Gregor Mendel 1822-1884 Lived in Austria (now part of Czechoslovakia) Was an Augustinian monkConducted breeding experiments in the monastery garden fromPublished in 1866 (just after Darwin was published)No one cared until 35 years later (about 1900)
6 Gregor MendelExperiment consisted of keeping amazingly accurate records of the garden peaHe chose the pea plant because he could get pure strains that had been produced over years by gardenersThe strains had many different varieties with contrasting traitsHe planted and kept records of over 30,000 plants
7 Gregor Mendel’s Results TraitFirst Generation (F1)Second Generation (F2)RatioYellow vs. Green PeasAll yellow6022 Yellow 2001 Green?Round vs. Wrinkled PeasAll round5474 Round 1850 WrinkledInflated vs. Constricted PodsAll Inflated882 Inflated 299 ConstrictedLong vs. Short StemsAll Long787 Long Stems 277 Short StemsColored vs. White FlowersAll Colored705 Colored 224 WhiteAxial vs. Terminal FlowersAll Axial651 Axial 207 TerminalGreen vs. Yellow PodsAll Green428 Green 224 Yellow
8 Gregor Mendel’s Results Did you see a trend?What is the final F2 ratio for each of the traits?
9 Gregor Mendel’s Results If you didn’t, go back and take a look againNotice that the trait in the F1 generation is always the larger number in the F2 generation
10 Gregor Mendel’s Results If you figured out the F2 ratio, you should have noticed something elseAlmost all of them are close to 3:1
11 Gregor Mendel’s Results TraitFirst Generation (F1)Second Generation (F2)RatioYellow vs. Green PeasAll yellow6022 Yellow 2001 Green3.01:1Round vs. Wrinkled PeasAll round5474 Round 1850 Wrinkled2.96:1Inflated vs. Constricted PodsAll Inflated882 Inflated 299 Constricted2.95:1Long vs. Short StemsAll Long787 Long Stems 277 Short Stems2.84:1Colored vs. White FlowersAll Colored705 Colored 224 White3.15:1Axial vs. Terminal FlowersAll Axial651 Axial 207 Terminal3.14:1Green vs. Yellow PodsAll Green428 Green 224 Yellow2.82:1
12 Gregor Mendel’s Results Why did all of the F2 generations have a three to one ratio when the F1 generation were all one trait?Because the pure parents each gave a gene or “factor” to each of the F1 offspring and one of those genes were dominant over the recessive gene
13 Gregor Mendel’s Results Yet, some of those F1 generations passed on the the genes to their F2 generations
14 Gregor Mendel’s Results The F2 generation must have had some of the traits from the P1 generation, but we were unable to see the recessive traits.They were masked or covered by the dominant trait.
15 Mendel’s First Principle Principle of Dominance and RecessivnessEach trait is controlled by a pair of factors (chromosomes)The dominant factor masks or hides the recessive factor
16 Genotype vs. PhenotypeGenotype describes the genetic make-up of the organismThe actual genesPhenotype describes the physical make-up of the organismWhat traits does the organism show
17 Mendel’s Second Principle The Principle of SegregationHeredity factors are determined by distinct factorsFor each trait, an individual carries two factors for each traitThe two factors of each trait segregate and end up in separate gametes
18 Mendel’s Second Principle Today, those factors are called genesPart of the DNAEach gene codes for one traitThose are called alleles
19 Mendel’s Second Principle If you did the cross below, what is the probabilty of each genotype?