SCIENCE 8 EXAM 4TH Q

• Genetics - the 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 - Due to different alleles
• Alleles - one of two or more versions of the DNA sequence
• 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 - traits are always expressed, even if only one copy of the dominant trait exists
• Recessive - traits are expressed only if both the connected alleles are recessive
• Punnett Square - A simple graphical representation used in genetics to predict the possible outcomes of a cross between two individuals or organisms
• Punnett Square - Developed by Reginald Punnett in the early 20th century
• Basic Overview of How Punnett Squares Work

  • Determining Parental Genotypes
  • Constructing the Square
  • Filling in the Square
  • Determining Offspring Genotypes
  • Analyzing Phenotypes
• Gregor Johann Mendel (1822 – 1884) - Biologist, meteorologist, mathematician, Augustinian friar, and abbot of St. Thomas' Abbey in Brno (Brünn), Margraviate of Moravia
• Gregor Johann Mendel (1822 – 1884) - Father of Genetics, Proposed the fundamental laws of inheritance, Experimented on Pisum sativum (common pea), Was able to discover the concept of genetics and heredity by observing common pea plants for 8 years
• Law of Segregation - Each individual possesses two alleles for each trait, one inherited from each parent.
• Law of Segregation - These alleles segregate (separate) during gamete formation so that each gamete receives only one allele for each trait
• Law of Segregation - 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
• Law of Independent Assortment –  that alleles of different genes assort independently during gamete formation
• Law of Dominance - An offspring that was developed from the crossbreeding of two parents, with each having true, different traits, will express the dominant trait and hide the 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 - To control the breeding process, Mendel manually transferred pollen from the stamen of one pea plant to the pistil of another. This allowed him to ensure specific parentage in his experiments
• Study of Traits - Mendel focused on several easily distinguishable traits in pea plants.
• Generation of Purebred Lines - 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. This ensured that all offspring would display the same traits as the parent.
• True breeders or Homozygous – the organism has two identical alleles of a particular trait
• Crossbreeding Experiments - Mendel then crossed purebred plants (F1) with different traits. For example, he would cross a tall plant with a short plant or a plant with yellow seeds with one with green seeds. (The offspring are the second filial generation or F2)
• Hybrid or Heterozygous – offspring produced by crossbreeding
• Laws of inheritance

  • Law of Segregation
  • Law of Independent Assortment
  • Law of Dominance
• Experiments and Discoveries

  • Selection of Pea Plants
  • Cross-Pollination
  • Study of Traits
  • Generation of Purebred Lines
  • Crossbreeding Experiments