Cystic Fibrosis Is an Autosomal Recessive Genetic Disorder That Most

Multiple Choice

Cystic fibrosis is an autosomal recessive genetic disorder that most severely affects the lungs and respiratory tract. Cystic fibrosis is caused by a mutation in the gene for the protein cystic fibrosis transmembrane regulator (CFTR) , which regulates the movement of chloride and sodium ions across epithelial cell membranes. When the CFTR gene is mutated in cystic fibrosis, the defective CFTR protein cannot transport ions properly, which results in too little water drawn across the membrane and the buildup of thick and sticky (viscous) mucus, especially in the airways. This leads to difficulty of breathing, frequent lung infections, and ultimately death.
Research has shown that some of the increased thickness and viscosity of the mucus in the respiratory tract is due to the presence of human DNA. If DNA is present in high concentrations in solution, the DNA molecules can get entangled and lead to a thick, viscous solution. To combat this, pharmaceutical companies have developed recombinant forms of the human deoxyribonuclease I (DNase I) protein. DNase I, after being translated and modified with sugar groups, is normally produced in human cells and possibly plays a role in DNA breakdown during apoptosis (programmed cell death) .
-A scientist produced a batch of recombinant DNase I in E. coli cells and a batch in mammalian cells. She placed 0.1 mg of the E. coli-derived DNase I in a vial containing a solution of DNA, and she placed 0.1 mg of the mammalian cell-derived DNase I in a separate vial containing the same solution of DNA. The initial viscosity of the DNA solutions was identical. What do you expect the viscosity of the DNA solutions to be after 10 minutes have passed, and why?

A) The viscosity of the mammalian cell DNase I vial will be lower than that of the E. coli DNase I vial because the mammalian cell DNase I will be functional and able to degrade the DNA.
B) The viscosity of the mammalian cell DNase I vial will be higher than that of the E. coli DNase I vial because the mammalian cell DNase I will be functional and able to degrade the DNA.
C) The viscosity of the E. coli DNase I vial will be lower than that of the mammalian cell DNase I vial because the E. coli DNase I will be functional and able to degrade the DNA.
D) The viscosity of the E. coli DNase I vial will be higher than that of the mammalian cell DNase I vial because the E. coli DNase I will be functional and able to degrade the DNA.