2. Support Your Explanation with Evidence The parents of the newborn baby girl are
happy that their first child was born without cystic fibrosis. But now they worry the
odds have increased that their next child will suffer from the disorder. Are their
concerns justified? Why or why not?

If both parents are healthy carriers of the gene that causes cystic fibrosis, then their concern is justified, since they have a 25% (1:4) chance of having a child with cystic fibrosis.

Explanation:

The gene that produces cystic fibrosis is called CFTR, and its inheritance pattern is autosomal recessive.  

Both parents may have the gene and not manifest the disease - healthy carriers - since the condition of homozygosity is necessary for cystic fibrosis to appear.  However, they are likely to have children who are healthy, healthy carriers or sick with cystic fibrosis:

Genotype of healthy carrier parents is N/cf, where N is the normal gene and Qf is the abnormal gene.

N/cf X N/cf

Alleles     N       cf

N            N/N    N/cf

cf            N/cf  cf/cf

The chances of having:

In this case, the concern of both parents is justified, since the probability of having a child with cystic fibrosis is 1:4.

Lerarn more:

Cystic fibrosis inheritance link