DNA Labeling Worksheet | Teaching Resource | Twinkl USA - Free Printable

Let’s go step by step to label the DNA diagram correctly.

We are given a word bank:
- deoxyribose sugar
- phosphate group
- nucleotide
- base pair
- nitrogenous base
- hydrogen bond

And we’re told to color and label parts based on letters:
- Thymine → red, label with T
- Cytosine → blue, label with C
- Guanine → green, label with G
- Adenine → purple, label with A

Also, we need to identify structural parts using the word bank.

Looking at the diagram (even though I can’t see it, I know standard DNA structure):

DNA is made of two strands twisted into a double helix. Each strand has repeating units called nucleotides.

Each nucleotide has 3 parts:
1. A deoxyribose sugar (5-carbon sugar)
2. A phosphate group
3. A nitrogenous base (A, T, C, or G)

The two strands are held together by hydrogen bonds between complementary bases:
- A pairs with T
- C pairs with G

So, in the diagram:

→ The circles usually represent phosphate groups
→ The pentagons (5-sided shapes) are deoxyribose sugars
→ The rectangles or shapes sticking inward are the nitrogenous bases
→ When two bases face each other across the middle, that’s a base pair
→ The whole unit (sugar + phosphate + base) is a nucleotide
→ The dashed or dotted lines between base pairs are hydrogen bonds

Now, for labeling with letters:

If you see a base labeled “T” — that’s thymine → color red
“C” = cytosine → blue
“G” = guanine → green
“A” = adenine → purple

In the diagram, if there’s a box around one full unit (sugar + phosphate + base), that’s a nucleotide.

If two bases are connected across the middle (like A-T or C-G), that’s a base pair.

The line connecting them? That’s the hydrogen bond.

So, putting it all together:

Labeling guide:

- Circle shape → phosphate group
- Pentagon shape → deoxyribose sugar
- Rectangle/shape inside → nitrogenous base
- Box around sugar+phosphate+base → nucleotide
- Two bases facing each other → base pair
- Dashed line between bases → hydrogen bond

Coloring:

- Wherever you see “T” → color red
- “C” → blue
- “G” → green
- “A” → purple

Final Answer:
Use the word bank to label:
- Phosphate group → circle
- Deoxyribose sugar → pentagon
- Nitrogenous base → inner rectangle
- Nucleotide → entire unit (sugar + phosphate + base)
- Base pair → two matching bases across from each other
- Hydrogen bond → line connecting base pairs

Color:
- T → red
- C → blue
- G → green
- A → purple