gen bio 2

• Cytogenetics


  Deals with chromosome structure and behavior during cell division
• Introduction to Inheritance


  Genetics answers most of our inquiries about how traits are transmitted from parents to their children
• Challenges faced by Mendel included previous notions of inheritance such as Pangenesis, Homunculus theory, and Blending theory
• Population genetics

  Deals with how forces of evolution influence genes in populations
• Pea Plant Hybridization

  Mendel chose the legumes garden peas or Pisum sativum for his hybridization experiments
• Branches of Genetics

  • Molecular genetics
  • Cytogenetics
  • Transmission genetics
  • Population genetics
• Gregor Mendel is known as the Father of Genetics
• The invention of the microscope made people believe that sperm cells bear a homunculus or little man
• Mendelian Laws of Inheritance


  Some of you may have inherited a widow’s peak and the ability to roll your tongue from your either or both of your parents, while some of you may lack these genetic traits
• Mendel's paper, "The Experiments on Plant Hybridization," was rediscovered independently by de Vries, Correns, and von Tschermak in the 1900s
• Peas are ideal for genetic studies because they exhibit vigorous growth, can self-fertilize, and can cross-fertilize
• Experiments of Gregor Mendel laid the foundation for the study of transmission genetics
• Pangenesis was the belief that seeds are produced in different organs and will later gather to form the offspring
• Mendel performed his pea plant studies in the Augustinian monastery of St. Thomas
• Introduction to Inheritance

  • Heredity
  • Variation
• Transmission genetics, also called classical genetics, is the oldest subdiscipline of genetics. It attempts to predict outcomes of reproduction
• Transmission genetics

  Deals with different patterns of inheritance
• Molecular genetics


  Deals with DNA and gene expression and regulation
• The blending theory of inheritance states that traits of parents blend every generation of offspring
• Rediscoverers of Mendel's work: Hugo de Vries (1848–1935), Carl Correns (1864–1933), Erich von Tschermak (1871–1962)
• Gene


  The basic unit of heredity that controls the expression of a biological characteristic
• Pisum sativum is an ideal model organism for genetic studies
• Alleles


  Alternative forms of a gene
• Mendel’s paper, The Experiments on Plant Hybridization, was rediscovered independently by de Vries, Correns, and von Tschermak


  1900s
• Phenotype


  Refers to the actual manifestation of genotypes into observable traits
• Generations in a Monohybrid Cross

  • P generation
  • F1 generation
  • F2 generation
• Observable traits controlled by genes

  • Tall
  • Round-seeded
• Genotype


  Refers to the set of alleles possessed by an organism
• Chromosome

  Consists of a DNA molecule, which serves as the repository of genetic information in cells
• Scientists who rediscovered Mendel's work

  • Hugo de Vries (1848–1935)
  • Carl Correns (1864–1933)
  • Erich von Tschermak (1871–1962)
• Parents blend every generation of offspring
• Monohybrid Cross

  Mating between two individuals involving one characteristic or one pair of contrasting traits
• In a heterozygous individual, one allele (dominant) completely masks
• Principle of Dominance


  In a heterozygous individual, one allele (dominant) completely masks the expression of the other allele (recessive)
• The phenotypes in the F2 generation occur in a ratio of 3:1
• Monohybrid Cross


  Genetic crosses involving a single trait
• Genotypes and Phenotypes

  • TT - tall
  • Tt - tall
  • tt - dwarf
• The dwarf trait disappeared in the F1 generation
• Law of Segregation

  The two alleles of a gene in an individual segregate or separate from each other during gamete formation
• Punnett Square


  Applying Punnett square to genetic crosses to determine genotypes and phenotypes