The CFTR gene is responsible for regulating the flow of water across cell membranes that produce mucus, sweat, saliva, and tears. Mucus is the substance that moistens and protects the lining of airways in the lungs, the digestive system, and other tissues in the body.
An inherited condition is caused by a mutation in the CFTR gene. For people with this CFTR mutation, the cells that make mucus produce a very thick mucus, which builds up. The buildup of thick mucus in the lungs can lead to severe breathing problems, such as frequent coughing and respiratory infections. A buildup of thick mucus in the pancreas can also disrupt digestion.
The diagram shows a pedigree for a family that is affected by this inherited condition.
The CFTR mutation most often occurs when three nucleotides from the gene sequence are deleted. The DNA sequence without the mutation and the DNA sequence with the mutation are shown.
DNA sequence without mutation:TAG TAG AAA CCA CAA
DNA sequence with mutation:TAG TAA CCA CAA
Which of the following is the mRNA sequence for the DNA sequence without the mutation?