DNA 2

• Allele


  Different versions of the same gene
• Homozygous


  Having two of the same alleles for a particular gene
• Heterozygous


  Having two different alleles for a particular gene
• Dominant allele

  The allele that gets expressed when present, regardless of whether the organism is homozygous or heterozygous for that allele
• Recessive allele


  The allele that only gets expressed when the organism is homozygous for that allele
• Genotype


  The entire collection of alleles that an organism has
• Phenotype


  The characteristics that an organism displays, which are determined by its genotype
• Genes code for particular types of proteins
• Characteristics are often determined by the interaction of multiple genes
• If an organism is heterozygous for a trait, the dominant allele will be expressed
• The only way to have a recessive trait expressed is if the organism is homozygous for the recessive allele