genetic key terms

• DNA

  • genetic material.
  • DNA is a polymer made up of two strands forming a double helix.
  • the DNA makes up chromosomes
• gene

  • a gene is a small section of DNA on a chromosome.
  • each gene codes for a particular sequence of amino acids which make protein~
• chromosome

  • a long coil of DNA
  • found in the nucleus
• genome

  • the entire genetic material of that organism
• allele

  • different versions of the same gene - dominant and recessive
• dominant

  • a dominant allele is always expressed
  • only one copy is needed
• recessive

  • only expressed if two copies are present
• homozygous

  • both alleles for a gene are the same (i.e. both dominant or both recessive)
• heterozygous

  • both alleles for a gene are different (i.e. one is dominant, the other is recessive
• genotype

  • the alleles present for a particular gene
• phenotype

  • the physical feature expressed for a particular gene
• single gene characteristics

  • some characteristics are controlled by only one gene (e.g. fur colour in mice, colour blindness in humans)
• multiple gene characteristics

  • most characteristics are controlled by many genes (e.g. height)