Genetics

• What are alleles?


  Different versions of the same gene

  • Most mammals have two alleles for each gene, 1 each from the mother and father
• What is an organisms genotype?

  The alleles that an organism has
• What is an organisms phenotype?


  The characteristics expressed by an organism
• What does it mean if an allele is dominant?

  Means an organism only needs to have one copy of the allele to display the characteristic of that allele
• What does it mean if an allele is recessive?

  Means an organism needs to have 2 copies of the allele to display that characteristic
• What does it mean if an organism is homozygous for a characteristic?

  Means it has two copies of the same allele for that characteristic

  e.g GG or gg
• What does it mean if an organism is heterozygous for a characteristic?

  It has two different alleles for that characteristic- Gg
• 2 characteristics controlled by a single gene:

  • Fur colour in mice
  • Red-green colour blindness in humans
• Are most characteristics controlled by single or multiple genes interacting?

  Multiple genes interacting
• What do punnet squares show?

  The possible outcome of a genetic cross and so the probability of offspring having a certain combination of alleles