Key Terms

• Genotype


  Genetic constitution of an organism
• Phenotype


  Expression of the gene and its interaction with the environment
• Homozygous


  A pair of homologous chromosomes carrying the same alleles for a single gene
• Heterozygous


  A pair of homologous chromosomes carrying 2 different alleles for a single gene
• Recessive Allele


  An allele only expressed if no dominant allele is present
• Dominant Allele


  An allele always expressed in a phenotype
• Codominant Allele


  Both alleles equally dominant, both expressed as phenotype
• Multiple Alleles


  More than 2 alleles for a gene
• Sex-Linkage


  A gene whos locus is on the X chromosome
• Autosomal Linkage


  Genes located on the same chromosome (not sex chromosome)
• Epistasis


  1 Gene modifies/masks expression of a different gene at a different locus
• Monohybrid


  Genetic inheritance cross of a characteristic determined by 1 gene
• Dihybrid


  Genetic inheritance cross of a characteristic determined by 2 genes