Genetic Terms

• Gene=


  A sequence of bases on a DNA molecule that codes for a protein (polypeptide)
• Allele


  a different version of a gene
• genotype


  the genetic constitution of an organism- the alleles an organism has
• phenotype


  the expression of the genetic constitution (genotype) and its interaction with the environment- an organism's characteristics
• allele?


  A version of a gene
• allele frequency


  The number of times an allele appears within a population’s gene pool
• dominant 


  Describes an allele that is always expressed. even when there is only one copy

  Represented by a capital letter.
• recessive 


  Describes an allele that is only expressed in the absence of a dominant allele. Represented by a small letter.

  the allele whose characteristic only appears in the phenotype if 2 copies are present
• codominant

  alleles that are both expressed in the phenotype - neither one is recessive

  When both alleles for a gene in a heterozygous organism equally contribute to the phenotype.
• LOCUS 


  the fixed position of a gene on a chromosome.
• alleles of a gene are found at the same locus on each chromosome in a pair
• Homozygote ?


  an organism that carries two copies of the same allele

  -eg bb or BB
• Heterozygote


  An organism that carries 2 different alleles
• Carrier


  a person carrying the allele which is not expressed in the phenotype but that can be passed on to offspring