DNA labeling activity for students to practice identifying nucleotides and completing complementary base pairs.

Problem Analysis:

The task involves solving a series of questions related to DNA structure and labeling. Let's break it down step by step:

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#### 1. Color and Label the Nucleotide
The image shows a nucleotide, which consists of three main parts:
- Phosphate group: Colored yellow.
- Sugar (deoxyribose): Not explicitly colored in the key but is part of the nucleotide.
- Base: One of the four nitrogenous bases (Adenine, Thymine, Cytosine, or Guanine).

From the provided key:
- Adenine (A) = Pink
- Thymine (T) = Blue
- Guanine (G) = Green
- Cytosine (C) = Red
- Phosphate group = Yellow

The nucleotide in the image should be labeled and colored accordingly based on its components.

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#### 2. Percentages of Each Base in a DNA Strand
The problem states that there are 30% adenines (A) in this DNA strand. We need to find the percentages of the other bases (T, C, G) assuming the DNA strand follows the base pairing rules (A pairs with T, and C pairs with G).

##### Base Pairing Rules:
- Adenine (A) always pairs with Thymine (T).
- Cytosine (C) always pairs with Guanine (G).

##### Given:
- Percentage of A = 30%

##### Step-by-Step Solution:
1. Total percentage of A + T:
Since A always pairs with T, the total percentage of A + T must be 50% (because A and T together make up half of the DNA bases in a double-stranded molecule).

\[
\text{Percentage of T} = 50\% - \text{Percentage of A}
\]
\[
\text{Percentage of T} = 50\% - 30\% = 20\%
\]

2. Total percentage of C + G:
Similarly, C always pairs with G, so the total percentage of C + G must also be 50%.

\[
\text{Percentage of C} + \text{Percentage of G} = 50\%
\]

Without additional information about the specific percentages of C and G, we cannot determine their individual values. However, we know their combined percentage is 50%.

##### Final Answer for Question 2:
\[
\boxed{A = 30\%, T = 20\%, C + G = 50\%}
\]

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#### 3. Complementary Sequence of DNA
The given DNA sequence is:
\[
\text{ACTGATCATAGTCCT}
\]

To find the complementary sequence, we use the base pairing rules:
- A pairs with T
- T pairs with A
- C pairs with G
- G pairs with C

##### Step-by-Step Solution:
Replace each base in the given sequence with its complementary base:
- A → T
- C → G
- T → A
- G → C

\[
\text{ACTGATCATAGTCCT} \rightarrow \text{TGACTAGTATCGAGGA}
\]

##### Final Answer for Question 3:
\[
\boxed{\text{TGACTAGTATCGAGGA}}
\]

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#### 4. Monomer of RNA
RNA (Ribonucleic Acid) is composed of monomers called nucleotides. However, the specific type of nucleotide in RNA differs from DNA because RNA uses ribose sugar instead of deoxyribose and uracil (U) instead of thymine (T).

##### Final Answer for Question 4:
\[
\boxed{\text{Nucleotide}}
\]

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Final Summary of Answers:

1. Color and Label the Nucleotide: Use the provided key to color the phosphate group yellow, the base according to its type (A = Pink, T = Blue, C = Red, G = Green), and label the components.
2. Percentages of Bases: \( A = 30\%, T = 20\%, C + G = 50\% \)
3. Complementary Sequence: \( \text{TGACTAGTATCGAGGA} \)
4. Monomer of RNA: \( \text{Nucleotide} \)

\[
\boxed{A = 30\%, T = 20\%, C + G = 50\%; \text{TGACTAGTATCGAGGA}; \text{Nucleotide}}
\]