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Work of Gregor Mendel

Work of Gregor Mendel. Section 11-1 Pages 263-266 Standard IV Objective 2a: Explain Mendel’s laws of segregation and independent assortment and their role in genetic inheritance. Genetics Vocabulary. Trait: specific characteristic

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Work of Gregor Mendel

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  1. Work of Gregor Mendel Section 11-1 Pages 263-266 Standard IV Objective 2a: Explain Mendel’s laws of segregation and independent assortment and their role in genetic inheritance.

  2. Genetics Vocabulary • Trait: specific characteristic • Gene: sequence of DNA that codes for a protein thus determining a trait • Alleles: different forms of a gene

  3. Gregor Mendel • Gregor Mendel—father of genetics • Conducted his work in the garden of a monastery—changed biology forever • Worked with true breeding pea plants • True breeding—produce identical offspring if allowed to self-pollinate • He looked at 7 different traits

  4. Alleles • Where do living organisms get alleles from? • Organisms receive one allele for each trait from each parent. • Principle of Dominance: some alleles are dominant and other are recessive • If a dominant allele is present, the organism will take on the characteristic of the dominant allele. • PTC paper

  5. Alleles • Representing different alleles • T (capital letter) = dominant trait • t (lower case) = recessive trait • For each trait there are two alleles (one from each parent) • Example: Plant height • TT and Tt • tt

  6. Probability • Principle of Probability: used to predict outcomes of genetic crosses • Homozygous – 2 identical alleles • Homozygous dominant (TT) • Homozygous recessive (tt) • Heterozygous – 2 different alleles (Tt)

  7. Mendel’s Crosses • Original pair of plants—P (parental) generation • The offspring of the P generation are called the F1 generation • Hybrid—the offspring of crosses between parents with different traits

  8. Results of Crosses • Mendel took the true breeding plants with contrasting characteristics and crossed them. • Tall plant x Short plant • What characteristics remained or were the offspring a blend of the two parents? • Took it another step: he allowed all hybrid plants to produce an F2 generation by self-pollination

  9. Genetic Vocabulary • Heterozygous—organisms that have two different alleles for the same trait • Homozygous—organisms that have two different alleles for a particular trait • Genotype—genetic makeup • Phenotype—physical characteristics

  10. Punnett Squares • Dad is heterozygous for a particular trait • Mom is homozygous recessive for the same trait • How do we predict outcomes?

  11. Picture Credits • http://history.nih.gov/exhibits/nirenberg/images/photos/01_mendel_pu.jpg • http://www.jbhs.k12.nf.ca/biology/photos/jillear2.jpg • http://sdmc.lit.org.sg/gedm/imageANDdata/gene.gif • http://www.naturalselectionreptiles.com/Genetics/allele.jpg • http://www.bbc.co.uk/schools/gcsebitesize/img/bipeas.gif • http://psychservices.ucsd.edu/resources_parents_web/resources_parents_images/resources_parents_help.jpg • http://images.google.com/imgres?imgurl=http://i21.photobucket.com/albums/b268/plopperscioly/punnettsquare.jpg&imgrefurl=http:// • http://stavos.homeip.net/detroitarchive/uploadcenter/images/tigon.jpg • http://cricket.biol.sc.edu/herb/CC/Centrosema_virginianum2.jpg • http://users.adelphia.net/~lubehawk/BioHELP!/psquare0.jpg

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