Question

Biologists use ball-and-stick models to study complex molecules by representing atoms with balls and bonds with sticks. DNA is a biological molecule that contains millions of atoms. What is a limitation of using a ball-and-stick model for DNA?

Some kinds of atoms that are found in DNA must be left out of the models.
DNA has so many atoms that the size and cost of a model could be too great.
It is impossible to distinguish different kinds of atoms with models.
The chemical bonds between the atoms in DNA must be part of the models.

Answer 1

I'd go with DNA has so many atoms that the size and cost of a model could be too great.

Answer 2

DNA has so many atoms that the size and cost of a model could be too great.

Step-by-step explanation:

Instead of explaining this answer in chemistry I would like to explain it in simple way. As we know DNA (polymer) is a type of Nucleic Acid which is made up of small repeating units (monomers) called as Nucleotides. The structure of Nucleotide is attached below. Let's take an example of DNA found in Human Chromosome. This DNA is about 2 inches long. Also, the size of one Nucleotide is around 3.3 Angstrom.

As,

1 Inch = 2.54 × 10⁸ Angstrom

Then,

2 Inches = 5.08 × 10⁸ Angstrom

So, we can calculate the number of Nucleotides in this chain of DNA as,

= 5.08 × 10⁸ ÷ 3.3

= 1.53 × 10⁸ Nucleotides

Now, assume that the balls and sticks required for making one one nucleotide costs 0.5 $ then 1.53 × 10⁸ Nucleotides will cost,

1 = 0.5 $

1.53 × 10⁸ = X $

Solving for X,

X = 1.53 × 10⁸ × 0.5 ÷1

X = 306000000 Dollars

Or,

Three Hundred and Six Million Dollars :)