GenBio Mendel's Laws of Inheritance

• Genes


  Units of inheritance
• Inheritance


  The process of how a child receives genetic information from the parent
• The whole process of heredity is dependent upon inheritance and it is the reason that the offsprings are similar to the parents
• It was only during the mid 19th century that people started to understand inheritance in a proper way
• Gregor Mendel


  Scientist who formulated certain laws to understand inheritance known as Mendel's laws of inheritance
• Mendel's Experiments


  1. Conducted hybridization experiments on the garden peas

  2. Chose distinct characteristics of the peas

  3. Conducted cross-pollination/artificial pollination on the pea lines that showed stable trait inheritance and underwent continuous self-pollination
• Pea plant


  • Can be easily grown and maintained
  • Naturally self-pollinating but can also be cross-pollinated
  • Annual plant, therefore, many generations can be studied within a short period of time
  • Has several contrasting characters
• Monohybrid Cross


  1. Took two pea plants of opposite traits (one short and one tall) and crossed them

  2. Found the first generation offspring were tall and called it F1 progeny

  3. Crossed F1 progeny and obtained both tall and short plants in the ratio 3:1
• Dihybrid Cross


  1. Considered two traits, each having two alleles

  2. Crossed wrinkled-green seed and round-yellow seeds

  3. Observed that all the first generation progeny (F1 progeny) were round-yellow

  4. Self-pollinated the F1 progeny and obtained 4 different traits: round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds in the ratio 9:3:3:1
• Genotype


  The genetic makeup of the plant
• Phenotype


  The physical appearance of the plant
• Alleles


  Genes are transferred from parents to the offspring in pairs
• Homozygous alleles


  Alleles are the same
• Heterozygous alleles


  Alleles are different
• Mendel's Laws


  • Law of Dominance
  • Law of Segregation
  • Law of Independent Assortment
• Law of Dominance


  Hybrid offspring will only inherit the dominant trait in the phenotype
• Law of Segregation


  Every individual possesses two alleles and only one allele is passed on to the offspring
• Law of Independent Assortment

  The inheritance of one pair of genes is independent of inheritance of another pair
• Law of segregation is the universally accepted law of inheritance
• The law of segregation is known as the law of purity of gametes because a gamete carries only a recessive or a dominant allele but not both the alleles
• Mendel picked pea plants in his experiments because the pea plant has different observable traits, can be grown easily in large numbers, its reproduction can be manipulated, and it has both male and female reproductive organs, so they can self-pollinate as well as cross-pollinate
• The main aim of Mendel's experiments was to determine whether the traits would always be recessive, whether traits affect each other as they are inherited, and whether traits could be transformed by DNA
• Genes

  Functional units of heredity made of DNA
• Chromosome


  • Made of DNA containing many genes
  • Each gene comprises a particular set of instructions for a function or protein coding
• There are about 30,000 genes in each cell of the human body
• DNA present in the gene comprises only 2 percent of the genome
• Studies have found the location of nearly 13,000 genes on each of the chromosomes
• William Bateson introduced the term genetics

  1905
• Wilhelm Johannes coined the term GENE

  1909
• Gene

  Symbolises hereditary
• Genes

  • Come in pairs like chromosomes
  • Each parent passes one copy of genes to their child
• Functions of Genes

  • Control the functions of DNA and RNA
  • Responsible for protein synthesis which controls all body activities
• Genes

  • Globin gene produces haemoglobin
• Heredity

  The natural phenomena of transferring traits or characteristics through genes from parents to offspring
• Conducted research and experiments on pea plants to prove the inheritance of traits

  Gregor Mendel
• Laws of Inheritance

  • Law of Dominance
  • Law of Segregation
  • Principle of Independent Assortment
• Traits


  Genetically determined characteristics transferred from parents to offspring through genes during sexual reproduction