inheritance

• characteristics are determined by the type and quantity of proteins synthesised some are controlled by the same gene most are a result of 2 or more genes interacting
• alleles- different versions of the same gene
• dominant alleles expressed when genotype contains recessive allele

  -must be no dominant allele in order for a recessive allele to be expressed in the phenotype
• phenotype: the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
• genotype: the genetic constitution of an individual organism.
• BB and bb

  homozygous
• Bb

  heterozygous
• girl-XX

  boy-XY
• punnet square - a diagram used to show the inheritance of traits from parents to offspring
• polybactyl- caused by a dominant allele

  cystic fibrosis- is due to a recessive allele