Inheritance and inherited disorders

• Alleles= different versions of the same gene. Can be different in everyone
• Homozygous= 2 identical alleles

  (Can be dominant or recessive)
• Heterozygous= two different alleles, one from each parent, e.g. Bb
• Dominant allele= the allele that is will always be expressed, e.g: B
• Recessive alleles= the allele that needs 2 copies to be expressed, e.g: b
• Phenotype= the result of the interaction of the genotype and the environment
• Genotype= the genetic makeup of an organism, the alleles it has ,e.g: homozygous or heterozygous
• Monohybrid Cross

  
• Punnett square is a diagram used to determine the probability of offspring from a cross

  Dd=2/4=50% dd=2/4=50%

  
• Carriers= people who have a defective gene but do not have the disease
• Cystic fibrosis= a recessive disorder that causes thick mucus to build up in the lungs and digestive system
• Polydactyly= a dominant disorder for extra fingers or toes
• Gene Therapy

  1. Cell doesn't have gene
  2. Use a virus to carry a healthy gene
  3. Virus enters cell and provides healthy gene
• Genetic screening raises economic, ethical and social concerns
• Embryo and fetus cells can be screened for alleles that cause genetic disorders