Biology worksheet diagram helping students label the components of DNA, including the sugar-phosphate backbone and nitrogenous bases.

Problem Analysis:

The task involves reviewing the structure of DNA and answering questions related to its components, replication process, historical discovery, shape, and terminology. Below is a detailed explanation and solution for each part of the problem.

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1. Labeling the Image:

The image shows a simplified representation of a DNA double helix. The task is to label the following components:

- Phosphates
- Deoxyribose
- Hydrogen Bonds
- Each of the four bases: adenine (A), guanine (G), cytosine (C), thymine (T)

#### Solution:
- Phosphates: These are located at the top of each nucleotide unit in the sugar-phosphate backbone. They are represented by the small circles at the top of the pentagons.
- Deoxyribose: This is the five-carbon sugar that forms part of the nucleotide. It is represented by the pentagon shapes.
- Hydrogen Bonds: These are the dashed lines connecting the complementary bases on opposite strands of the DNA double helix. They hold the two strands together.
- Bases:
- Adenine (A): Pairs with Thymine (T). In the image, "A" is already labeled.
- Guanine (G): Pairs with Cytosine (C). In the image, "G" is already labeled.
- Cytosine (C): Pairs with Guanine (G).
- Thymine (T): Pairs with Adenine (A).

#### Labeling Instructions:
- Place "Phosphate" labels near the small circles at the top of the pentagons.
- Place "Deoxyribose" labels near the pentagon shapes.
- Place "Hydrogen Bonds" labels near the dashed lines connecting the bases.
- Identify and label the remaining bases as "C" (cytosine) and "T" (thymine) based on their pairing patterns:
- Adenine (A) pairs with Thymine (T).
- Guanine (G) pairs with Cytosine (C).

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2. The Process by Which DNA Makes a Copy is Called:

The process by which DNA makes a copy of itself is called DNA replication.

#### Solution:
- DNA replication

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3. What Two Scientists Are Credited with Establishing the Structure of DNA?

James Watson and Francis Crick are credited with discovering the double-helix structure of DNA in 1953. Their work was supported by data from Rosalind Franklin and Maurice Wilkins, who provided X-ray crystallography images of DNA.

#### Solution:
- James Watson and Francis Crick

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4. What is the Shape of a DNA Molecule?

The DNA molecule has a double helix shape. This means it resembles a twisted ladder, with the sides made up of alternating deoxyribose sugars and phosphates, and the rungs made up of hydrogen-bonded base pairs.

#### Solution:
- Double helix

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5. The Two Sides of the Molecule Are Said to Be "Antiparallel." What Does Antiparallel Mean?

In the context of DNA, "antiparallel" refers to the orientation of the two strands in the double helix. The two strands run in opposite directions:
- One strand runs in the 5' to 3' direction.
- The other strand runs in the 3' to 5' direction.

This antiparallel arrangement allows the complementary bases to pair correctly (A-T and G-C) and ensures proper alignment during processes like replication and transcription.

#### Solution:
- Antiparallel means that the two strands of DNA run in opposite directions (5' to 3' and 3' to 5').

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Final Answers:

1. Label the image as follows:
- Phosphates: Small circles at the top of the pentagons.
- Deoxyribose: Pentagon shapes.
- Hydrogen Bonds: Dashed lines connecting the bases.
- Bases: Label "C" (cytosine) and "T" (thymine) based on pairing rules.
2. The process by which DNA makes a copy is called: DNA replication.
3. The two scientists credited with establishing the structure of DNA are: James Watson and Francis Crick.
4. The shape of a DNA molecule is: Double helix.
5. Antiparallel means: The two strands of DNA run in opposite directions (5' to 3' and 3' to 5').

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Boxed Final Answer:

\[
\boxed{
\begin{array}{l}
\text{1. Label the image as described above.} \\
\text{2. DNA replication} \\
\text{3. James Watson and Francis Crick} \\
\text{4. Double helix} \\
\text{5. The two strands run in opposite directions (5' to 3' and 3' to 5').}
\end{array}
}
\]