Video Transcript
Cystic fibrosis is an inherited
disease that affects the lungs and reproductive system of the sufferer. Why would somebody with a history
of cystic fibrosis in the family want their genome mapped before they had a
child? (A) To determine how easy it would
be for them to become pregnant. (B) To determine the sex of the
child before it was born. (C) To determine if they were a
carrier of the disease. (D) To determine the
characteristics of the child.
This question presents us with an
inherited disease called cystic fibrosis that affects the lungs, the digestive
system, and the reproductive system of the sufferer. Let’s discuss how this disease is
inherited and how genome mapping relates to this.
Cystic fibrosis results from a
mutation in the cystic fibrosis transmembrane conductance regulator, or CFTR,
gene. Cystic fibrosis is recessive,
meaning two copies of the mutated gene are needed to produce cystic fibrosis.
You’ll recall that most of our
cells contain two copies of each chromosome. The CFTR gene is located on
chromosome seven. And in the situation represented
here, this individual has two copies of the mutant CFTR gene, one from each of their
two copies of chromosome seven. If someone only has one copy of the
mutated CFTR gene, then they will not develop cystic fibrosis because they need two
copies. Someone who carries a copy of the
mutant allele without themselves showing the disease are called carriers.
When this individual who’s a
carrier produces gametes, such as eggs or sperm, chromosome seven will be randomly
allocated to these cells. So some gametes will have the
mutant CFTR allele, while others will not. These gametes can then combine with
another individual’s gametes who may also be a carrier. This would produce an embryo that
carries two mutant copies of the CFTR gene. The resulting child would have
cystic fibrosis.
One way to tell if an individual is
a carrier or not for the mutant CFTR gene is to map their genome. That way, we would have a sequence
of their two copies of the CFTR gene and could see if it was mutated or not.
Therefore, the reason someone with
a history of cystic fibrosis would want to have their genome mapped before having
children is given by answer choice (C): to determine if they were a carrier of the
disease.
