Cystic fibrosis is an inherited condition in humans. The allele for cystic fibrosis is recessive.
a.[1]
Which of the following describes a dominant allele?
- An allele expressed in the phenotype only if two copies are present
- An allele expressed in the phenotype even if only one copy is present
- An allele that is only inherited from the maternal parent
b.[1]
Figure 1 shows the inheritance of cystic fibrosis in one family.
The symbol of a shaded square is not in the key for Figure 1. What would this symbol represent?
c.
[3]
Parents 1 and 2 in Figure 1 have a child with cystic fibrosis and some children without cystic fibrosis. Complete the genetic diagram to show the possible genotypes of the children. Use the following symbols:
- FFF = allele for normal mucus production (dominant)
- fff = allele for cystic fibrosis (recessive)
| Person 2: FFF | Person 2: fff | |
|---|---|---|
| Person 1: FFF | Box (i) | FfFfFf |
| Person 1: fff | Box (ii) | Box (iii) |
Identify the genotypes for:
- Box (i)
- Box (ii)
- Box (iii)
d.[1]
What is the phenotype of a person with the genotype FfFfFf?
e.[1]
What percentage of the offspring shown in the genetic diagram will have cystic fibrosis?