genetics

• Allele


  Different versions of the same gene
• Homozygous


  Having two of the same alleles for a gene
• Heterozygous


  Having two different alleles for a gene
• Dominant allele


  The allele that gets expressed when present, regardless of the other allele
• Recessive allele

  The allele that only gets expressed when two copies are present (homozygous recessive)
• Genotype


  The entire collection of alleles an organism has
• Phenotype


  The characteristics an organism displays, determined by its genotype
• Genes code for particular types of proteins
• There are often multiple forms of the same protein, each with a different genetic code (alleles)
• We have two copies of every gene, one from each parent
• If the two alleles are the same, the organism is homozygous
• If the two alleles are different, the organism is heterozygous
• When an organism is heterozygous, one allele will be dominant and the other recessive
• The dominant allele is always expressed, even in heterozygous organisms
• The only way to have a recessive trait expressed is if the organism is homozygous recessive
• Genotype refers to the genetic makeup, while phenotype refers to the expressed characteristics