Worksheet: Inherited Disorders
In this worksheet, we will practice using genetic diagrams to predict probabilities of offspring inheriting recessive, dominant or sex-linked disorders.
A person who is heterozygous for the cystic fibrosis allele (Ff) reproduces with a person who is homozygous dominant (FF). Which of the Punnett squares shows the correct cross?
F f F FF Ff F FF Ff
F f F FF FF F FF FF
F F F FF FF f ff ff
f f F Ff Ff F Ff Ff
Cystic fibrosis is an inherited disorder caused by a recessive allele. Which of the following best explains what this means?
- AA person must have three copies of the allele for cystic fibrosis to be expressed in the phenotype.
- BA person must have two copies of the allele for cystic fibrosis to be expressed in the phenotype.
- CCystic fibrosis only affects offspring once every two generations.
- DA person can carry more than one copy of the allele and not have cystic fibrosis.
- EA person will express the disease in their phenotype even if only one allele is in their genotype.
Polydactyly is caused by a dominant allele.
A female heterozygous for polydactyly reproduces with a heterozygous male. What is the probability that the offspring will have polydactyly?
A male heterozygous for polydactyly reproduces with a female who is homozygous recessive. What is the probability that the offspring will have polydactyly?
PKU is an inherited disorder caused by a recessive allele (r). A male who is homozygous for the disorder reproduces with a heterozygous female.
What is the genotype of the male homozygous for PKU?
What is the genotype of the female heterozygous for PKU?
What is the probability that a child of theirs will inherit the disorder PKU?
What is the probability that a child of theirs will be a carrier of the PKU allele?