DEFINITIONS

• GENOTYPE?

  genetic constitution of an organism, describing the alleles an organism has
• PHENOTYPE?

  expression of the genetic constitution of an organism and its interactions with the environment

  -> observable/ biochemical characteristics
• GENE?

  nucleotide base sequence of DNA that codes for the AA sequence of a polypeptide and a functional RNA
• LOCUS?

  location of a gene on a chromosome
• ALLELE?

  one of a number of alternative forms of a gene
• KEY FEATURES OF ALLELES?

  • only one allele of a gene found at the locus of one chromosome
  • in diploid organisms, chromosomes occur in pairs (homologous chromosomes)
  • therefore there are two loci, each with one allele of a gene
• HOMOZYGOUS?

  when the allele on each of the chromosomes is the same
• HETEROZYGOUS?

  when both of the alleles on each of the chromosome are different
• DOMINANT?

  condition where the allele is always expressed in the phenotype
• RECESSIVE?

  condition in which the effect of an allele is only apparent in the phenotype of a diploid organism in the presence of another identical allele
• MULTIPLE ALLELES?

  if there are more than two alleles of a gene
• CODOMINANCE?

  if both alleles contribute to the phenotype
• WHAT CHANGES THE GENOTYPE INTO THE PHENOTYPE?

  environmental effects
• WHAT LEADS TO THE ALLELE PAIRINGS?

  gametes only possess one allele therefore random fusion occurs