bio 3

• Genetics


  The science of heredity and variation
• Gregor Johann Mendel


  • An Austrian monk who studied patterns of inheritance among garden peas (Pissum sativum); father of Genetics
• Principles of Genetics


  • Heredity - faithful transmission of trait from the parent to the offspring
  • Variation - differences in the traits of parents to offspring as a result of genetic recombination
• Character


  Morphological feature that is transmitted from parent to offspring
• Trait


  Variations of a character
• Allele


  Alternative form of the same character
• Alleles exist in pairs
• Dominant allele


  Is expressed when present. It is represented by an uppercase letter
• Recessive allele


  Is expressed only in the absence of the dominant allele. It is represented by a lowercase letter
• Violet flower is dominant over white flower
• Phenotype


  Character that is observed in an organism
• Genotype


  Allelic composition of a phenotype

  
• Homozygous


  If it contains the same type of alleles
• Heterozygous


  If it contains two different alleles for a character

  
• Law of Segregation


  States that the pair of alleles for a character separate from each other during gamete formation such that each gamete receives one allele
• Law of Independent Assortment

  States that during gamete formation, the members of one allelic pair separate from each other independent of other allelic pairs
• Parental (P) generation


  Maternal and paternal parents whose gametes fuse to form a zygote
• Filial (F) generation


  The offspring
• F1


  Results from mating of parents
• F2


  Results from mating of F1
• Hybridization

  Mating of two varieties
• Monohybrid Cross

  Involves a single character
• Monohybrid Cross

  • Among Mendel's garden peas, purple flower color is dominant over white flower color

  
• Dihybrid Cross


  Involves two characters
• Dihybrid Cross


  • In Mendel's experiment, round seed shape is dominant to wrinkled seed shape, while yellow seed color is dominant to green seed color

  
• Complete dominance


  Occurs when the dominant allele is expressed in the homozygous and heterozygous condition
• Human traits with complete dominance

  • Free earlobe, Widows peak, Ability to curl tongue, Polydactyly (presence of extra digit)
• Incomplete dominance


  Occurs when the F1 generation shows a phenotype that is due to incomplete expression of the dominant allele
• Incomplete dominance


  • In snapdragons (Antirrhinum), red flower exhibit incomplete dominance over white flower
• Codominance


  Occurs when two dominant alleles are expressed in the F1 generation
• Codominance


  • Inheritance of ABO and MN blood groups, and the coat color of Shorthorn breed of cattle
• Chromosome Theory of Inheritance


  States that genes are present in chromosomes and during gamete formation, the chromosomes segregate and assort independently

  
• Gene


  Refers to a segment of the DNA that code for a specific protein. It is transmitted from parents to offspring
• Gene locus


  Specific site in the chromosome where the gene is located
• Mutation


  Refers to alteration in the base sequences of a gene
• Wild type


  Normal phenotype of a character
• Mutant


  Alternative trait of a wild type
• Recessive mutant trait


  • Body color of the fruit fly Drosophila melanogaster
• Dominant mutant trait


  • Eye shape of the fruit fly Drosophila melanogaster
• Dominant lethal allele


  Kills the individual in the homozygous and heterozygous forms