Unit 1: Cell Processes and Transport Notes online exercise for ... - Free Printable

Let’s go through the worksheet step by step to fill in the blanks correctly.

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Section: The Nucleus of a Cell

> The nucleus is called the ________________ ________________ of the cell because it holds the instructions to make all the ________________ a body needs. These instructions are in the form of DNA.

✔ From biology basics:
- The nucleus is often called the “control center” or “command center” of the cell.
- It holds instructions to make proteins — which are essential for body functions.

So:
→ control center
→ proteins

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Section: The Structure of DNA

> Inside the nucleus, the DNA is packaged into threadlike structures called ________________. DNA supplies ________________ responsible for different ________________ and for proper functioning of the body.

✔ DNA is packaged into chromosomes.
→ Chromosomes carry genes, which code for different traits (like eye color, height, etc.).

So:
→ chromosomes
→ genes
→ traits

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> The DNA molecule is a ________________ ________________, a double-stranded structure that looks like a spiral ladder.

✔ DNA is known as a double helix — that’s its famous spiral shape.

So:
→ double helix

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> The sides of the ladder are made of ________________ and ________________. The rungs of the ladder are ________________ ________________.

✔ In DNA:
- Sides = sugar and phosphate molecules (alternating)
- Rungs = nitrogenous base pairs (adenine-thymine, guanine-cytosine)

So:
→ sugar
→ phosphate
→ nitrogen bases (or “base pairs” — but “nitrogen bases” is more accurate for what makes up the rungs)

*(Note: Some textbooks say “phosphate and sugar” — order doesn’t matter here since they alternate.)*

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Now let’s compile all answers:

The Nucleus of a Cell:
- control center
- proteins

The Structure of DNA:
- chromosomes
- genes
- traits
- double helix
- sugar
- phosphate
- nitrogen bases

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Final Answer:
control center, proteins, chromosomes, genes, traits, double helix, sugar, phosphate, nitrogen bases