DNA - The Double Helix, Coloring Worksheet - Free Printable

Let’s solve this step by step.

We are looking at two main structures: DNA (on the left) and Messenger RNA (on the right). We need to match parts of these molecules using the labels given.

First, look at the bottom right — there are four nucleotides shown with letters: G, A, C, T. These are nitrogenous bases found in DNA. In RNA, instead of T (thymine), we have U (uracil), but here we’re comparing DNA structure to mRNA.

Now, let’s identify what each label points to:

- Label D on the DNA molecule points to one of the “rungs” of the ladder — that’s a base pair. But more specifically, since it’s pointing to the shape that connects across, it’s likely indicating a nitrogenous base.

- Label P on the DNA is pointing to the outer backbone — that’s the phosphate group, which alternates with sugar to form the sides of the DNA ladder.

On the Messenger RNA side:

- Label P again points to the backbone — same as in DNA, so that’s also phosphate.

- Label R points to the single strand’s “rung” — that’s a nitrogenous base in RNA. Since RNA uses A, U, C, G, and we see shapes matching those, R is pointing to a base.

But wait — let’s check the key at the bottom right. It shows:

- Circle = phosphate
- Pentagon = sugar (deoxyribose in DNA, ribose in RNA)
- Hexagon or other shape = nitrogenous base (G, A, C, T)

So in both DNA and RNA:

- The circle is always phosphate → labeled P in both diagrams.
- The pentagon is sugar → not labeled directly, but part of the backbone.
- The attached shape (hexagon etc.) is the base → labeled D in DNA, R in RNA.

Therefore:

→ D = Nitrogenous base (in DNA)
→ P = Phosphate group (in both DNA and RNA)
→ R = Nitrogenous base (in RNA)

Also note: In DNA, bases come in pairs (A-T, G-C), while in RNA, it’s single-stranded, so only one base per position.

Final check: All labels point correctly based on standard molecular biology diagrams.

Final Answer:
D = Nitrogenous base
P = Phosphate group
R = Nitrogenous base