Genetics

• Genetics


  Study of heredity and variation
• Genes


  Sequences of nucleotides in DNA that serve as the basic physical and functional traits of heredity
• Heredity


  Study of the passing of characteristics or traits through combined genetic materials of the parents to their children
• Variation


  Any difference between the individuals in a species or groups of organisms
• Variation is due to different alleles
• Alleles


  One of two or more versions of the DNA sequence
• Usually have 2 alleles per gene
• Punnett Square


  1. Determining Parental Genotypes

  2. Constructing the Square

  3. Filling in the Square

  4. Determining Offspring Genotypes
• Punnett Square


  A simple graphical representation used in genetics to predict the possible outcomes of a cross between two individuals or organisms
• Punnett Square was developed by Reginald Punnett in the early 20th century and has since become a fundamental tool in understanding basic principles of heredity
• Genotype


  Genetic makeup, or the combination of alleles represented by letters that correspond to specific alleles
• Phenotype


  Observable characteristics of an organism resulting from its genotype
• Dominant trait


  Traits are always expressed, even if only one copy of the dominant trait exists
• Recessive trait


  Traits are expressed only if both the connected alleles are recessive
• Selection of Pea Plants


  Mendel chose peas because they were easy to grow, had several easily observable traits with distinct variations, and had a short, reproductive cycle
• Cross-Pollination


  Mendel manually transferred pollen from the stamen of one pea plant to the pistil of another to control the breeding process
• Traits Mendel studied in pea plants


  • Seed
  • Flower
  • Pod
  • Stem
• Generation of Purebred Lines


  1. Mendel first created purebred lines (first filial generation, or F1) of pea plants for each trait by self-fertilizing plants with identical traits for several generations

  2. True breeders or Homozygous - the organism has two identical alleles of a particular trait
• Crossbreeding Experiments


  1. Mendel crossed purebred plants (F1) with different traits

  2. Hybrid or Heterozygous - offspring produced by crossbreeding, the pair of alleles differs because they came from parents with different traits
• Law of Segregation


  Each individual possesses two alleles for each trait, one inherited from each parent. These alleles segregote (separate) during gamete formation so that each gamete receives only one allele for each trait. During fertilization, the offspring receives one allele for each trait from each parent, resulting in the formation of a genotype.
• Law of Independent Assortment


  Inheritance of one trait does not influence the inheritance of another trait, that alleles of different genes assort independently during gamete formation, directly leads to the diversity in characteristics