GCSE Combined Science (AQA)

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Cystic Fibrosis

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Inheritance, Variation and Evolution Reproduction

Cystic Fibrosis

3:01 Sex Determination and Inherited Disorders
Spec 4.6.1.7
Previous Embryo Screening Next Variation
  • Cystic fibrosis is a genetic disorder affecting cell membranes in the lungs and digestive system.
  • It is characterized by sticky mucus that blocks airways.
  • The disorder is caused by a recessive allele, represented by the letter D in this context.
  • Two recessive alleles (dd) are necessary for a person to have cystic fibrosis.
  • If one parent has two dominant alleles (DD), none of their children will inherit cystic fibrosis.
  • If one parent is homozygous dominant (DD) and the other is homozygous recessive (dd), all offspring will be heterozygous (Dd) and will not have cystic fibrosis.
  • If both parents are homozygous recessive (dd), all their offspring will have cystic fibrosis.
  • If one parent is heterozygous (Dd) and the other is homozygous recessive (dd), there is a 50% chance their child will have cystic fibrosis.
  • If both parents are heterozygous (Dd), there is a 25% chance their child will inherit cystic fibrosis.
  • Punnet squares are used to predict the probability of inheriting cystic fibrosis based on parental genotypes.
  • Understanding these genetic principles is crucial for predicting inheritance patterns in exams and analyzing family trees for genetic disorders like cystic fibrosis.

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