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Mendelian Genetics

Mendelian Genetics. While assigned to teach, he was also assigned to tend the gardens and grow vegetables for the monks to eat. Augustinian Monk at Brno Monastery in Austria (now Czech Republic). Gregor Mendel “Father of Genetics”.

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Mendelian Genetics

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  1. Mendelian Genetics While assigned to teach, he was also assigned to tend the gardens and grow vegetables for the monks to eat. Augustinian Monk at Brno Monastery in Austria (now Czech Republic) Gregor Mendel “Father of Genetics” Not a great teacher but well trained in math, statistics, probability, physics, and interested in plants and heredity. Mountains with short, cool growing season pea (Pisum sativum) was an ideal crop plant.

  2. http://academic.evergreen.edu/v/vivianoc/homunculus.gif History in 1860 : • Discovered Genes as Particles of Inheritance • Discovered Patterns of Inheritance • Discovered Genes Come from Both Parents • Egg + Sperm = Zygote • Nature vs Nurture • Sperm means Seed (Homunculus) • Discovered One Form of Gene (Allele) Dominant to Another • Discovered Recessive Allele Expressed in Absence of Dominant Allele

  3. Mendel worked with peas (Pisum sativum) • Good choice for environment of monastery • He got good varieties for testing • Pureline • Scientists of 1860s could not understand math • His work lost in journals for 50 years! • Rediscovered in 1900s independently by 3 scientists “re-discovered" in 1900, Hugo de Vries, Carl Correns, and Erich von Tschermak, and were initially very controversial. The “re-discovery” were combined with chromosome theory of inheritance by Thomas Hunt Morgan in 1915, they became the core of classical genetics.

  4. One Example of Mendel’s Work Tall x Dwarf Phenotype Genotype P DD dd Homozygous Dominant Homozygous Recessive All Tall Clearly Tall is Inherited… What happened to Dwarf? F1 Dd Heterozygous Tall is dominant to Dwarf Use D/d rather than T/t for symbolic logic F1 x F1 = F2 possible gametes Punnett Square: D d 3/4 Tall 1/4 Dwarf F2 D Tall DD Tall Dd possible gametes d Tall Dd Dwarf dd Dwarf is not missing…just masked as “recessive” in a diploid state… there IS a female contribution.

  5. F1 x F1 = F2 F2 possible gametes Punnett Square: D d D Tall DD Tall Dd possible gametes d Tall Dd Dwarf dd Mendel as a Scientist Test Cross: Unknown Tall x Dwarf dd possible gametes If Unknown is DD: d d D Tall Dd Tall Dd possible gametes Test Progeny All Tall D Tall Dd Tall Dd 1/3 of F2 Tall are DD 2/3 of F2 Tall are Dd possible gametes If Unknown is Dd: d d D Tall Dd Tall Dd possible gametes Test Progeny Half Tall Half Dwarf d Dwarf dd Dwarf dd

  6. Another Example of Mendel’s Work Green x Yellow Phenotype P gg GG Genotype Homozygous Recessive Homozygous Dominant All Yellow Clearly Yellow is Inherited… What happened to Green? F1 Gg Yellow is dominant to Green Use G/g rather than Y/y for symbolic logic Heterozygous F1 x F1 = F2 possible gametes NEVER use G/Y or g/y Punnett Square: G g F2 3/4 Yellow 1/4 Green G Yellow GG Yellow Gg possible gametes g Yellow Gg Green gg Green is not missing…just masked as “recessive” in diploid state

  7. F1 x F1 = F2 F2 possible gametes Punnett Square: G g G Yellow GG Yellow Gg possible gametes g Yellow Gg Green gg Mendel as a Scientist Test Cross: Unknown Yellow x Green gg possible gametes If Unknown is GG: g g G Yellow Gg Yellow Gg possible gametes Test Progeny All Yellow G Yellow Gg Yellow Gg 1/3 of F2 Yellow are GG 2/3 of F2 Yellow are Gg possible gametes If Unknown is Gg: g g G Yellow Gg Yellow Gg possible gametes Test Progeny Half Yellow Half Green g Green gg Green gg

  8. Law of Segregation (The "First Law") The Law of Segregation states that when any individual produces gametes, the copies of a gene separate, so that each gamete receives only one copy. A gamete will receive one allele or the other. The direct proof of this was later found when the process of meiosis came to be known. In meiosis the paternal and maternal chromosomes get separated and the alleles with the characters are segregated into two different Law of Independent Assortment (The "Second Law") The Law of Independent Assortment, also known as "Inheritance Law", states that alleles of different genes assort independently of one another during gamete formation. While Mendel's experiments with mixing one trait always resulted in a 3:1 ratio between dominant and recessive phenotypes, his experiments with mixing two traits (dihybrid cross) showed 9:3:3:1 ratios . But the 9:3:3:1 table shows that each of the two genes are independently inherited with a 3:1 ratio. Mendel was success with his experiment because he was lucky, the genes were not located in the same chromosome. What would happen if the genes were in the same chromosome?

  9. Will be continued next week

  10. Apriem 6. Indah • Aria 7. Bondan + • Chandra • Raka • Sutrisno

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