Genetics

• Character or Trait: A potentially variable quality or quantity in an organism
• Hybrid: The offspring of two different varieties
• Monohybrid Cross: Studying the inheritance of a single character in a hybridization experiment
• P: Parental generation, starting point for experiment
• F1: First filial generation, offspring of P generation
• F2: Second filial generation, offspring of F1 generation
• Gene: A sequence of genetic material (DNA)
• Locus: The place on a chromosome where a gene is located (loci)
• Allele: One form of a gene found at a particular locus
• Diploid: Having two alleles at each locus
• Haploid: Having one allele at each locus
• Homozygous: The two alleles at a particular locus are the same
• Heterozygous: The two alleles at a particular locus are different
• Dominant: An allele that is fully expressed in a heterozygote
• Recessive: An allele that is not expressed at all in a heterozygote
• Genotype: The specific alleles that an organism has
• Phenotype: The character that the organism has (due to genotype and environment)
• Codominant: Both alleles are fully expressed in a heterozygote
• Incomplete Dominance: Both alleles contribute partially to the phenotype in a heterozygote
• Pleiotropy: The genotype at a single locus influences more than one trait
• Dihybrid Cross: A hybridization experiment in which the inheritance of two traits is studied
• Dependent Assortment: The alleles at two loci segregate together into gametes
• Independent Assortment: The alleles at two loci segregate individually into gametes
• Polygenic Traits: The phenotype is influenced by many loci
• True-breeding: New generation has the same characteristics
• Particles of inheritance: Purple flower (P) and white flower (p)
• 46 chromosomes (23 pairs)
• Sex chromosomes are X and Y chromosomes
• Carrier: Carries a recessive allele for a genetic trait or mutation (Hh)
• In sexually reproducing organisms, alleles are carried by gametes
• At the locus for flower colour, the allele for purple flowers is dominant, while the allele for white flowers is recessive. If half of the alleles at this locus in a population of pea plants are for purple flowers, what proportion of pea plants would have white flowers?

  0.5 x 0.5 = 0.25 or 25%
• When a trait is dominant, only one allele is required for the trait to be observed
• In incomplete dominance, neither allele is completely dominant
• • Genetic drift is the random change in allele frequencies in a population due to chance