Law of inheritance

• Genetics


  The study of heredity and variation. It aims to understand how traits can be passed on to the next generation and how variation arises.
• Branches of Genetics

  • Molecular genetics
  • Cytogenetics
  • Transmission genetics
  • Population genetics
• Molecular genetics


  Deals with DNA and gene expression and regulation.
• Cytogenetics


  Deals with chromosome structure and behavior during cell division.
• Transmission genetics


  Deals with different patterns of inheritance.
• Population genetics


  Deals with how forces of evolution influence genes in populations.
• Transmission genetics, also called classical genetics, is the oldest subdiscipline of genetics. It attempts to predict outcomes of reproduction.
• Gregor Johann Mendel


  19th century Moravian monk, the "Father of Genetics", formulated the ideas of inheritance based on simple hybridization experiment with pea plants, scientifically known as Pisum sativum
• Mendel took the path to priesthood when he entered Augustinian monastery of St. Thomas and became monk. This is also where he performed his pea plant studies.
• Mendel chose the legumes garden peas or Pisum sativum for his hybridization experiments.
• Pea Plant Hybridization

  • They exhibit vigorous growth.
  • They can self-fertilize.
  • They can cross-fertilize.
• Challenges faced by Mendel

  • Pangenesis
  • Homunculus theory
  • Blending theory
• Pangenesis


  The belief that seeds are produced in different organs and will later on gather to form the offspring.
• Homunculus theory


  The invention of the microscope made people believe that sperm cells bear a homunculus or little man.
• Blending theory of inheritance


  States that traits of parents blend every generation of offspring.
• Mendel's paper, The Experiments on Plant Hybridization, was rediscovered independently by de Vries, Correns, and von Tschermak in 1900s.
• Rediscovery of Mendel's Work

  • Hugo de Vries (1848–1935)
  • Carl Correns (1864–1933)
  • Erich von Tschermak (1871–1962)
• Chromosome


  A DNA molecule that serves as the repository of genetic information in cells.
• Homologous chromosomes


  Chromosomes that occur in pairs.
• Homologous chromosomes

  • Paternal (from the father or male parent)
  • Maternal (from the mother or female parent)
• Gene


  The basic unit of heredity that controls the expression of a biological characteristic.
• Characteristic


  A heritable feature of an organism.
• Alleles


  The alternative forms of a gene.
• Genotype


  The set of alleles possessed by an organism.
• Homozygous


  The genotype where the alleles are identical.
• Heterozygous


  The genotype where the alleles are different.
• Phenotypes


  The actual manifestation of genotypes into observable traits.
• Pea Plant Characters


  • Gregor Mendel utilized seven characteristics of peas in his hybridization experiments. Each exists in two variants.
• William Bateson


  He was the first person to use the term genetics to describe the study of heredity and biological inheritance.
• Monohybrid Cross


  A mating between two individuals involving one characteristic or one pair of contrasting traits.
• P generation


  The parental generation consists of the true-breeding initial parents.
• F1 generation


  The first filial generation consists of the offspring of the P generation.
• F2 generation


  The second filial generation consists of the offspring of F1 gen.
• Principle of Dominance / Law of Dominance


  In a heterozygous individual, one allele (dominant) completely masks the expression of the other allele (recessive).
• Law of Segregation


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


  He created the Punnett square in the year 1905 in Arizona State University to illustrate some of Mendel's discoveries including the segregation of DNA into different gametes upon gamete formation.
• Dihybrid Cross


  A mating between two individuals involving two characteristics or two pairs of contrasting traits.
• Used to illustrate some of Mendel's discoveries including the segregation of DNA into different gametes upon gamete formation

  1905 punnet
• Punnett Square


  Used to apply Mendel's principles to genetic crosses
• Dihybrid Cross


  A mating between two individuals involving two characteristics or two pairs of contrasting traits