DNA and Genes worksheet illustrating the structure of DNA with labeled parts for educational purposes.

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Worksheet: DNA and Genes

#### 1. Label the diagram:
Label the following parts of the DNA molecule:
- Deoxyribose
- Phosphate group
- Nitrogenous base
- Hydrogen bonds
- Sugar-phosphate backbone

> Diagram Description (based on typical DNA structure):
> - A double helix with two strands.
> - Each strand has alternating sugar and phosphate groups (backbone).
> - Nitrogenous bases (A, T, C, G) are paired in the center via hydrogen bonds.
> - The two strands run antiparallel (one 5' to 3', the other 3' to 5').

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Solution:

Let’s label each part:

1. Deoxyribose: The five-carbon sugar found in DNA. It is attached to the phosphate group and nitrogenous base.
→ *Label the sugar rings on each strand.*

2. Phosphate group: The phosphorus-containing group that links sugars together.
→ *Label the phosphate units connecting the sugar rings.*

3. Nitrogenous base: The nitrogen-containing molecules that pair across the helix (A-T, C-G).
→ *Label the letters A, T, C, G in the center of the helix.*

4. Hydrogen bonds: The weak bonds between complementary bases (A-T has 2 H-bonds; C-G has 3).
→ *Draw short lines between paired bases (e.g., between A and T).*

5. Sugar-phosphate backbone: The alternating sugar and phosphate chain forming the outer edges of the helix.
→ *Label the entire outer edge of each strand as "sugar-phosphate backbone."*

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2. Complete each statement:

(a) In DNA, ________ pairs with ________, and ________ pairs with ________.
> Answer:
> In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).

(b) In DNA, ________ always forms hydrogen bonds with guanine (G).
> Answer:
> In DNA, cytosine (C) always forms hydrogen bonds with guanine (G).

(c) The sequence of ________ makes up the genetic information of an organism.
> Answer:
> The sequence of nitrogenous bases makes up the genetic information of an organism.

(d) The process of ________ produces more copies of a segment of genetic information, which is passed on to new cells.
> Answer:
> The process of DNA replication produces more copies of a segment of genetic information, which is passed on to new cells.

(e) The nucleotide sequence in DNA is called a ________.
> Answer:
> The nucleotide sequence in DNA is called a gene (or genetic code, depending on context — but most accurately, a gene is a specific sequence that codes for a protein or RNA).

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✔ Final Answers Summary:

#### Diagram Labels:
- Deoxyribose: sugar ring
- Phosphate group: phosphate unit
- Nitrogenous base: A, T, C, G
- Hydrogen bonds: lines between A-T and C-G
- Sugar-phosphate backbone: outer side of each strand

#### Fill-in-the-blank Answers:
(a) adenine (A), thymine (T), cytosine (C), guanine (G)
(b) cytosine (C)
(c) nitrogenous bases
(d) DNA replication
(e) gene

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