SCIENTIFIC INQUIRY

Question

Suppose you are a research assistant in a lab studying DNA
-binding proteins. You have been given the amino acid sequences of all the proteins encoded by the genome of a certain species and have been asked to find candidate proteins that could bind DNA
. What type of amino acids would you expect to see in the DNA
-binding regions of such proteins?

A. DNA has many phosphate groups along the backbone of each strand, so the molecule has many positive charges. Therefore, you might expect a DNA -binding protein to have many Amino acids with negatively charged side chains.
B. DNA has many phosphate groups along the backbone of each strand, so the molecule has many negative charges. Therefore, you might expect a DNA -binding protein to have many amino acids with positively charged side chains.
C. DNA has two strands that wind around an imaginary axis, forming a long double helix. Therefore, you might expect a DNA -binding protein to be fibrous to fit into and bind to a DNA
molecule.
D. DNA has many hydroxyl groups along the backbone of each strand, so the molecule has many negative charges. Therefore, you might expect a DNA -binding protein to have many amino acids with positively charged side chains.

Answer 1

The correct answer is:

B. DNA has many phosphate groups along the backbone of each strand, so the molecule has many negative charges. Therefore, you might expect a DNA-binding protein to have many amino acids with positively charged side chains.

This is because the phosphate groups in the DNA backbone carry a negative charge, which would attract positively charged amino acids (such as lysine and arginine) in DNA-binding proteins. This positive charge can facilitate binding through electrostatic interactions, allowing the protein to effectively adhere to the negatively charged DNA.