inherited disorders

• Inherited disorders


  A group of conditions that can be passed on in certain alleles and inherited from a person's parents
• Inherited disorders


  • Polydactyly
  • Cystic fibrosis
• Polydactyly


  • A condition in which a baby is born with extra fingers or toes
  • Doesn't usually cause any other problems
  • Caused by a dominant allele
• Genetic diagram for polydactyly

  1. Cross a heterozygous individual who has polydactyly with a homozygous normal individual

  2. Gametes are one dominant polydactyly allele and three normal alleles

  3. Possible offspring are two heterozygous individuals that do have polydactyly and two homozygous normal individuals
• Probability of polydactyly phenotype in offspring is 50%
• Cystic fibrosis


  • Caused by a recessive allele
  • Disorder of the cell membranes
  • Results in thick sticky mucus in the airways of the lungs and in the pancreas
• One in 25 people are heterozygous carriers of the cystic fibrosis allele
• Genetic diagram for cystic fibrosis

  1. Cross two heterozygous carriers

  2. Parent genotypes are heterozygous

  3. Gametes are one dominant allele and one recessive allele

  4. Offspring genotypes are one homozygous dominant, two heterozygous, and one homozygous recessive

  5. Offspring phenotypes are three normal and one with cystic fibrosis
• Embryo screening


  Process of examining the genes of an embryo created through IVF to check for genetic disorders before implantation
• Advantages of embryo screening

  • Reduces overall suffering from genetic disorders
  • Saves money on treating genetic disorders
• Concerns about embryo screening

  • Implies people with genetic problems are less desirable
  • Could lead to screening for other traits like eye colour or physique in the future
• UK has laws in place to prevent screening for traits other than genetic disorders