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Mendelian Genetics

Mendelian Genetics. Objectives:. After completing this lab topic you should be able to : Explain the different terminologies associated with Mendelian genetics. Should be able to perform monohybrid and dihybrid crosses. . A Brief History.

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Mendelian Genetics

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  1. Mendelian Genetics

  2. Objectives: • After completing this lab topic you should be able to : • Explain the different terminologies associated with Mendelian genetics. • Should be able to perform monohybrid and dihybrid crosses.

  3. A Brief History • The science of heredity stems from Gregor Mendel: 1865 • Improved upon by Correns, deVries, and vonTschermak: 1900 • Continues to be a main branch of scientific study and advancement

  4. Study of Genetics is useful • Explains evolution which is central dogma of all biology • Human behavior • Crop improvement • Biomedical engineering • Insulin • Gene therapy

  5. Abbreviations • P = parents being crossed • F1 = children of the crossed P • F2 = children from F1’s (grandchildren of original P) • X = cross

  6. Some nifty terminology • Monohybrid cross a mating that tracks the inheritance of ONE trait. Dihybrid = TWO traits being observed • DNA--coils--chromosome…a gene is a particular part of a chromosome, and is thus DNA • Homologous chromosomes similar genes, one from each parent

  7. Alleles alternate versions of the same gene • Contributes to genetic variation = GOOD. • Homozygous same allele from mom and dad • Ex: AA, aa • Heterozygousdifferent allele from mom and dad • Ex: Aa, Bb • Hemizygous sex chromosomes are different • Homomorphic (XX female), heteromorphic (XY male)

  8. Dominant allele always appears in phenotype whether homozygous or heterozygous • AA or Aa, the A trait is still expressed • Recessive allele only expressed when homozygous • Codominance both alleles are expressed in heterozygotes • Blood type (A, B, AB, O)

  9. Incomplete dominance also known as semidominance; heterozygote is intermediate in expression between two different homozygotes • Genotype genetic makeup or allelic constitution of an individual • AA, Aa, aa, etc. • Phenotype the expression or appearance of an individual • AA and Aa would have the same phenotype, although their genotype if different

  10. Red and White are incompletely expressed as Pink

  11. Wild type vs. mutant • Wild type is “normal” expression of trait • Mutant is not normal, or mutated • Ratios proportion of offspring that have a given genotype or phenotype • Show modes of inheritance • AA, Aa, aa = 1:2:1 genotypic, 3:1 phenotypic

  12. Today’s lab will entail the following: • Examine the slide of grasshopper testis (demo). • Examine the electron micrographs of meiosis. • Lab exercise to mimic meiosis using pipe cleaners and beads (handout).

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