DNA Replication Practice Worksheet for students to learn about DNA structure and replication process.
DNA replication practice worksheet with questions and diagrams for students to answer and replicate DNA strands.
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Step-by-step solution for: DNA Replication Worksheet | PDF
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Show Answer Key & Explanations
Step-by-step solution for: DNA Replication Worksheet | PDF
Let’s go through each question one by one. I’ll explain the thinking behind each answer so you understand why it’s correct.
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1. DNA replication occurs in the (nucleus/cytoplasm) of the cell.
In eukaryotic cells (like human or plant cells), DNA is stored in the nucleus. Replication happens there before cell division. Prokaryotes don’t have a nucleus, but since this worksheet is likely for general biology, we assume eukaryotic cells.
✔ Answer: nucleus
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2. The sugar found in a DNA molecule is called (ribose/deoxyribose).
DNA = Deoxyribonucleic Acid → “deoxy” means it has deoxyribose sugar. RNA has ribose.
✔ Answer: deoxyribose
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3. Replication is considered a (conservative/semi-conservative) process because the new strands are half old DNA and half new DNA.
Semi-conservative means each new DNA molecule has one original strand and one newly made strand. That’s exactly what happens.
✔ Answer: semi-conservative
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4. The following strand of DNA is undergoing replication. What is the complementary strand?
Original top strand:
A T G C C C G A C T G C A
Complementary bottom strand must pair as:
- A ↔ T
- T ↔ A
- G ↔ C
- C ↔ G
So let’s match them:
Top: A T G C C C G A C T G C A
Bottom: T A C G G G C T G A C G T
That matches the given bottom row — so they’re already showing the complementary strand! But the question says “What is the complementary strand?” — probably asking to confirm or write it out.
But looking at the table, both rows are filled. Maybe it’s just checking if you know how pairing works. Since the bottom row is already written correctly, perhaps no action needed? Wait — maybe the question is implying that only the top row is given, and you need to fill the bottom? But in the image, both are filled. Hmm.
Actually, re-reading: “The following strand of DNA is undergoing replication. What is the complementary strand?” — and then two rows are shown. Probably, the top is the template, and the bottom is the answer. So the complementary strand is the bottom row: T A C G G G C T G A C G T
But since it's already written, maybe the question is just testing if you recognize it’s correct. Let’s move on — perhaps later questions will clarify.
Wait — actually, looking ahead, questions 9, 11, and 15 also say “Replicate the following strand” and show two rows — meaning the second row is the replicated/complementary strand. So for Q4, the complementary strand is the second row: T A C G G G C T G A C G T
✔ Answer: T A C G G G C T G A C G T
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5. When pairing bases during replication thymine always pairs with (adenine/cytosine).
Base pairing rules: A-T, G-C. Thymine (T) always pairs with Adenine (A).
✔ Answer: adenine
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6. The percent of guanine in a strand of DNA is always equal to the percent of (adenine/cytosine).
Chargaff’s Rule: %G = %C, and %A = %T. So guanine equals cytosine.
✔ Answer: cytosine
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7. When the DNA strand unzips, the (hydrogen/nitrogen) bonds are broken between the bases.
The bases are held together by hydrogen bonds. Nitrogen is part of the base structure, but the bonds between bases are hydrogen bonds.
✔ Answer: hydrogen
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8. If a strand of DNA has 20% thymine, there is (20%/30%) guanine in the strand.
If T = 20%, then A = 20% (because A=T). So A+T = 40%. Therefore, G+C = 60%. And since G=C, each is 30%.
✔ Answer: 30%
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9. Replicate the following strand of DNA
Given top strand:
T A C G T G G A C C T A T
Complementary strand should be:
T → A
A → T
C → G
G → C
T → A
G → C
G → C
A → T
C → G
C → G
T → A
A → T
T → A
So:
Top: T A C G T G G A C C T A T
Bottom: A T G C A C C T G G A T A
Which matches the given bottom row. So again, the complementary strand is: A T G C A C C T G G A T A
✔ Answer: A T G C A C C T G G A T A
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10. If a cell has 33% adenine in a strand of DNA, the percentage of thymine is (33%/22%)
A = T, so if A is 33%, T is also 33%.
✔ Answer: 33%
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11. Replicate the following strand of DNA
Top strand:
T A G T A T G G C T A T G
Complement:
T→A, A→T, G→C, T→A, A→T, T→A, G→C, G→C, C→G, T→A, A→T, T→A, G→C
So:
Top: T A G T A T G G C T A T G
Bottom: A T C A T A C C G A T A C
Matches given bottom row.
✔ Answer: A T C A T A C C G A T A C
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12. A molecule of DNA is made up of building blocks called (nucleotides/nitrogen bases).
Nucleotides are the full building blocks — each contains a sugar, phosphate, and nitrogen base. Nitrogen bases are parts of nucleotides.
✔ Answer: nucleotides
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13. DNA contains the instructions for the building of (carbohydrates/proteins).
DNA codes for proteins via genes. Carbohydrates are built using enzymes (which are proteins), but DNA directly instructs protein synthesis.
✔ Answer: proteins
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14. The shape of a DNA molecules is considered a (double/single) helix.
Famous double helix structure discovered by Watson and Crick.
✔ Answer: double
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15. Replicate the following strand of DNA
Top strand:
A G C T A T T C C G A G T
Complement:
A→T, G→C, C→G, T→A, A→T, T→A, T→A, C→G, C→G, G→C, A→T, G→C, T→A
So:
Top: A G C T A T T C C G A G T
Bottom: T C G A T A A G G C T C A
Matches given bottom row.
✔ Answer: T C G A T A A G G C T C A
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Now, compiling all final answers clearly:
Final Answer:
1. nucleus
2. deoxyribose
3. semi-conservative
4. T A C G G G C T G A C G T
5. adenine
6. cytosine
7. hydrogen
8. 30%
9. A T G C A C C T G G A T A
10. 33%
11. A T C A T A C C G A T A C
12. nucleotides
13. proteins
14. double
15. T C G A T A A G G C T C A
---
1. DNA replication occurs in the (nucleus/cytoplasm) of the cell.
In eukaryotic cells (like human or plant cells), DNA is stored in the nucleus. Replication happens there before cell division. Prokaryotes don’t have a nucleus, but since this worksheet is likely for general biology, we assume eukaryotic cells.
✔ Answer: nucleus
---
2. The sugar found in a DNA molecule is called (ribose/deoxyribose).
DNA = Deoxyribonucleic Acid → “deoxy” means it has deoxyribose sugar. RNA has ribose.
✔ Answer: deoxyribose
---
3. Replication is considered a (conservative/semi-conservative) process because the new strands are half old DNA and half new DNA.
Semi-conservative means each new DNA molecule has one original strand and one newly made strand. That’s exactly what happens.
✔ Answer: semi-conservative
---
4. The following strand of DNA is undergoing replication. What is the complementary strand?
Original top strand:
A T G C C C G A C T G C A
Complementary bottom strand must pair as:
- A ↔ T
- T ↔ A
- G ↔ C
- C ↔ G
So let’s match them:
Top: A T G C C C G A C T G C A
Bottom: T A C G G G C T G A C G T
That matches the given bottom row — so they’re already showing the complementary strand! But the question says “What is the complementary strand?” — probably asking to confirm or write it out.
But looking at the table, both rows are filled. Maybe it’s just checking if you know how pairing works. Since the bottom row is already written correctly, perhaps no action needed? Wait — maybe the question is implying that only the top row is given, and you need to fill the bottom? But in the image, both are filled. Hmm.
Actually, re-reading: “The following strand of DNA is undergoing replication. What is the complementary strand?” — and then two rows are shown. Probably, the top is the template, and the bottom is the answer. So the complementary strand is the bottom row: T A C G G G C T G A C G T
But since it's already written, maybe the question is just testing if you recognize it’s correct. Let’s move on — perhaps later questions will clarify.
Wait — actually, looking ahead, questions 9, 11, and 15 also say “Replicate the following strand” and show two rows — meaning the second row is the replicated/complementary strand. So for Q4, the complementary strand is the second row: T A C G G G C T G A C G T
✔ Answer: T A C G G G C T G A C G T
---
5. When pairing bases during replication thymine always pairs with (adenine/cytosine).
Base pairing rules: A-T, G-C. Thymine (T) always pairs with Adenine (A).
✔ Answer: adenine
---
6. The percent of guanine in a strand of DNA is always equal to the percent of (adenine/cytosine).
Chargaff’s Rule: %G = %C, and %A = %T. So guanine equals cytosine.
✔ Answer: cytosine
---
7. When the DNA strand unzips, the (hydrogen/nitrogen) bonds are broken between the bases.
The bases are held together by hydrogen bonds. Nitrogen is part of the base structure, but the bonds between bases are hydrogen bonds.
✔ Answer: hydrogen
---
8. If a strand of DNA has 20% thymine, there is (20%/30%) guanine in the strand.
If T = 20%, then A = 20% (because A=T). So A+T = 40%. Therefore, G+C = 60%. And since G=C, each is 30%.
✔ Answer: 30%
---
9. Replicate the following strand of DNA
Given top strand:
T A C G T G G A C C T A T
Complementary strand should be:
T → A
A → T
C → G
G → C
T → A
G → C
G → C
A → T
C → G
C → G
T → A
A → T
T → A
So:
Top: T A C G T G G A C C T A T
Bottom: A T G C A C C T G G A T A
Which matches the given bottom row. So again, the complementary strand is: A T G C A C C T G G A T A
✔ Answer: A T G C A C C T G G A T A
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10. If a cell has 33% adenine in a strand of DNA, the percentage of thymine is (33%/22%)
A = T, so if A is 33%, T is also 33%.
✔ Answer: 33%
---
11. Replicate the following strand of DNA
Top strand:
T A G T A T G G C T A T G
Complement:
T→A, A→T, G→C, T→A, A→T, T→A, G→C, G→C, C→G, T→A, A→T, T→A, G→C
So:
Top: T A G T A T G G C T A T G
Bottom: A T C A T A C C G A T A C
Matches given bottom row.
✔ Answer: A T C A T A C C G A T A C
---
12. A molecule of DNA is made up of building blocks called (nucleotides/nitrogen bases).
Nucleotides are the full building blocks — each contains a sugar, phosphate, and nitrogen base. Nitrogen bases are parts of nucleotides.
✔ Answer: nucleotides
---
13. DNA contains the instructions for the building of (carbohydrates/proteins).
DNA codes for proteins via genes. Carbohydrates are built using enzymes (which are proteins), but DNA directly instructs protein synthesis.
✔ Answer: proteins
---
14. The shape of a DNA molecules is considered a (double/single) helix.
Famous double helix structure discovered by Watson and Crick.
✔ Answer: double
---
15. Replicate the following strand of DNA
Top strand:
A G C T A T T C C G A G T
Complement:
A→T, G→C, C→G, T→A, A→T, T→A, T→A, C→G, C→G, G→C, A→T, G→C, T→A
So:
Top: A G C T A T T C C G A G T
Bottom: T C G A T A A G G C T C A
Matches given bottom row.
✔ Answer: T C G A T A A G G C T C A
---
Now, compiling all final answers clearly:
Final Answer:
1. nucleus
2. deoxyribose
3. semi-conservative
4. T A C G G G C T G A C G T
5. adenine
6. cytosine
7. hydrogen
8. 30%
9. A T G C A C C T G G A T A
10. 33%
11. A T C A T A C C G A T A C
12. nucleotides
13. proteins
14. double
15. T C G A T A A G G C T C A
Parent Tip: Review the logic above to help your child master the concept of dna replication activity worksheet.
