Cystic Fibrosis

    Cards (23)

    • What inherited disorder is discussed in this video?
      Cystic fibrosis
    • What should you be able to do by the end of this video?
      Describe cystic fibrosis and complete Punnett squares
    • What are alleles?
      Different versions of a gene
    • What is the difference between dominant and recessive alleles?
      Dominant alleles are expressed with one copy
    • What is the symbol for the dominant allele for normal cell membrane function?
      Capital C
    • What is the symbol for the recessive allele for defective cell membranes?
      Lowercase c
    • How many copies of the defective allele must a person inherit to have cystic fibrosis?
      Two copies
    • What do we call a person with one defective allele and one normal allele?
      A carrier of the cystic fibrosis allele
    • What is the genotype of a man who is a carrier of the cystic fibrosis allele?
      Heterozygous (one normal, one defective)
    • What is the genotype of a woman who does not have cystic fibrosis and is not a carrier?
      Homozygous for the normal allele
    • What is the first step in constructing a Punnett square for cystic fibrosis?
      Write down the genotypes of the gametes
    • What percentage of offspring will be carriers when a heterozygous man and a homozygous normal woman have children?
      50%
    • What is the genotype of the offspring that are carriers of cystic fibrosis?
      Capital C lowercase c
    • What is the ratio of carriers to non-carriers from the cross of a heterozygous man and a homozygous normal woman?
      1:1
    • What is the probability that all offspring could be carriers or all could be unaffected?
      These are just probabilities
    • What happens when two carriers of the cystic fibrosis allele have children?
      25% will have cystic fibrosis
    • What is the ratio of offspring from two carriers of cystic fibrosis?
      1:2:1 ratio
    • What is the percentage of offspring that are not affected at all from two carriers?
      25%
    • What is the percentage of offspring that are carriers from two carriers?
      50%
    • What is the percentage of offspring that have cystic fibrosis from two carriers?
      25%
    • What are the key points about cystic fibrosis inheritance?
      • Cystic fibrosis is a disorder of cell membranes.
      • Controlled by a single gene with two alleles.
      • Dominant allele (normal function): Capital C.
      • Recessive allele (defective function): Lowercase c.
      • Two copies of the defective allele are needed for cystic fibrosis.
      • Carriers have one normal and one defective allele.
    • What are the outcomes of genetic crosses involving cystic fibrosis?
      • Heterozygous man and homozygous normal woman:
      • 50% carriers, 50% not affected (1:1 ratio).
      • Two carriers:
      • 25% not affected, 50% carriers, 25% with cystic fibrosis (1:2:1 ratio).
    • What should students practice regarding genetic crosses?
      • Complete Punnett square diagrams.
      • Express outcomes as percentages and ratios.
      • Understand probabilities in genetic outcomes.