Inherited disorders

• What are inherited disorders?

  Conditions passed on through certain alleles
• What is polydactyly?

  Condition with extra fingers or toes
• How is polydactyly inherited?

  It is caused by a dominant allele
• What happens if one allele is for polydactyly?

  The disorder will still be expressed
• What is the genotype of a heterozygous individual with polydactyly?

  One dominant and one normal allele
• What is the outcome of crossing a heterozygous polydactyly individual with a homozygous normal individual?

  • Gametes: 1 dominant polydactyly, 3 normal
  • Offspring: 2 heterozygous (polydactyly), 2 homozygous normal
  • Phenotype ratio: 1:1 (50% chance of polydactyly)
• What causes cystic fibrosis?

  A recessive allele
• What is cystic fibrosis a disorder of?

  Cell membranes
• What is the result of cystic fibrosis on the body?

  Thick sticky mucus in various organs
• What allele represents cystic fibrosis?

  Lowercase f
• How many recessive alleles are needed for cystic fibrosis to manifest?

  Two recessive alleles
• What is the genotype of most people regarding cystic fibrosis?

  Normal homozygous dominant genotype
• What do we call individuals with one copy of the cystic fibrosis allele?

  Carriers
• What is the outcome of crossing two carriers of cystic fibrosis?

  • Parent phenotypes: both normal
  • Parent genotypes: both heterozygous
  • Offspring: 1 homozygous dominant, 2 heterozygous, 1 homozygous recessive
  • Phenotype ratio: 3 normal, 1 cystic fibrosis
• What is embryo screening?

  Checking embryos for genetic disorders
• What happens if a genetic disorder is found during embryo screening?

  Parents may discard that embryo
• What are the advantages and concerns of embryonic screening?

  Advantages:

  • Reduces suffering from health problems
  • Saves money on treatments

  
  

  Concerns:

  • Implies genetic problems are undesirable
  • Potential for screening non-health traits
• What is a concern regarding the perception of individuals with genetic disorders?

  They may be seen as less desirable
• What laws exist in the UK regarding embryo screening?

  Many laws prevent unethical screening
• What should you be able to discuss for your exam regarding embryo screening?

  The pros and cons of the process