DNA Replication Review Worksheet - Free Printable
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Step-by-step solution for: DNA Replication Review Worksheet
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Step-by-step solution for: DNA Replication Review Worksheet
Here is the complete solution to your DNA Replication Review Worksheet, with clear, accurate answers and explanations for each question:
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1. What does DNA stand for?
→ Deoxyribonucleic Acid
*Explanation:* DNA is the molecule that carries genetic instructions in all known living organisms. The name reflects its chemical structure: “deoxyribo” refers to the sugar (deoxyribose), and “nucleic acid” refers to its classification as a nucleic acid.
---
2. What is DNA’s primary function?
→ To store and transmit genetic information necessary for the growth, development, functioning, and reproduction of all known living organisms.
*Explanation:* DNA contains the instructions for building proteins, which carry out most of the work in cells and determine traits.
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4. What are the subunits called that make up DNA?
→ Nucleotides
*Explanation:* DNA is a polymer made of repeating units called nucleotides. Each nucleotide consists of a sugar, phosphate group, and nitrogenous base.
*(Note: Question 3 is missing — likely a typo in the worksheet.)*
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5. Name the 3 parts of a DNA nucleotide.
→ 1. Deoxyribose sugar
→ 2. Phosphate group
→ 3. Nitrogenous base
*Explanation:* These three components form the basic building block of DNA. The sugar and phosphate form the backbone; the base carries the genetic code.
---
6. Sketch and label a DNA nucleotide.
*(Since I can’t draw here, I’ll describe it clearly for you to sketch):*
Draw a central pentagon (representing deoxyribose sugar).
Attach a circle labeled “P” (phosphate) to one corner of the pentagon.
Attach a rectangle or hexagon labeled with a letter (A, T, C, or G) to another corner — this is the nitrogenous base.
Label each part: “Phosphate,” “Deoxyribose Sugar,” “Nitrogenous Base.”
---
7. Name the 4 nitrogen bases on DNA.
→ Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
*Explanation:* These bases pair specifically (A-T, C-G) and form the “rungs” of the DNA ladder.
---
8. What is the difference between a purine & a pyrimidine?
→ Purines are double-ring nitrogenous bases (Adenine and Guanine). Pyrimidines are single-ring nitrogenous bases (Thymine and Cytosine).
*Explanation:* This structural difference affects how they pair — purines always pair with pyrimidines to maintain uniform width of the DNA helix.
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9. Name 2 purines.
→ Adenine (A) and Guanine (G)
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10. Name 2 pyrimidines.
→ Thymine (T) and Cytosine (C)
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11. Who is responsible for determining the structure of the DNA molecule & in what year was this done?
→ James Watson and Francis Crick in 1953
*Explanation:* They built the first correct model of DNA’s double helix using data from Rosalind Franklin and Maurice Wilkins.
---
12. The model of DNA is known as a ________________ because it is composed of two ______________ chains wrapped around each other.
→ Double helix
→ Antiparallel
*Explanation:* The “double helix” describes the twisted ladder shape. The two strands run in opposite directions (antiparallel) — one 5’→3’, the other 3’→5’.
---
13. What makes up the sides of a DNA molecule?
→ Alternating sugar (deoxyribose) and phosphate groups
*Explanation:* These form the “backbone” of the DNA strand, providing structural support.
---
14. What makes up the "steps" of a DNA molecule?
→ Pairs of nitrogenous bases (base pairs)
*Explanation:* The “steps” are formed by hydrogen-bonded complementary base pairs: A-T and C-G.
---
15. How did Rosalind Franklin contribute to determining the structure of DNA?
→ She produced high-resolution X-ray diffraction images of DNA (especially Photo 51), which revealed the helical structure and key dimensions like the spacing between bases and the diameter of the helix.
*Explanation:* Her data was critical to Watson and Crick’s model, though she was not credited at the time.
---
16. What type of bonds holds the DNA bases together? Are they strong or weak bonds?
→ Hydrogen bonds
→ They are weak bonds
*Explanation:* Hydrogen bonds allow the DNA strands to separate easily during replication and transcription. Two H-bonds hold A-T; three hold C-G.
---
17. What makes up the "backbone" of the DNA molecule?
→ Alternating deoxyribose sugars and phosphate groups
*Explanation:* The sugar-phosphate backbone runs along the outside of the helix and provides structural integrity.
---
18. On DNA, a _______________ base will always pair with a _______________ base.
→ Purine
→ Pyrimidine
*Explanation:* Due to size constraints, purines (double ring) must pair with pyrimidines (single ring) to keep the helix width constant.
*(Alternatively, you could say: “Adenine” → “Thymine”, or “Guanine” → “Cytosine” — but the blank format suggests the general category.)*
---
20. How many base pairs are in a full turn or twist of a DNA molecule?
→ Approximately 10 base pairs per turn
*Explanation:* In B-DNA (the most common form), there are about 10.5 base pairs per helical turn, but textbooks often round to 10 for simplicity.
---
21. Name the complementary base pairs on DNA.
→ Adenine (A) pairs with Thymine (T)
→ Cytosine (C) pairs with Guanine (G)
*Explanation:* Complementary base pairing follows Chargaff’s rules: A=T and C=G. This ensures accurate replication.
---
✔ Bonus Tip for Study:
Remember the mnemonic: “A-T, C-G — Always Together, Can’t Get apart!”
---
Let me know if you’d like a printable version or diagrams to go with these answers!
---
1. What does DNA stand for?
→ Deoxyribonucleic Acid
*Explanation:* DNA is the molecule that carries genetic instructions in all known living organisms. The name reflects its chemical structure: “deoxyribo” refers to the sugar (deoxyribose), and “nucleic acid” refers to its classification as a nucleic acid.
---
2. What is DNA’s primary function?
→ To store and transmit genetic information necessary for the growth, development, functioning, and reproduction of all known living organisms.
*Explanation:* DNA contains the instructions for building proteins, which carry out most of the work in cells and determine traits.
---
4. What are the subunits called that make up DNA?
→ Nucleotides
*Explanation:* DNA is a polymer made of repeating units called nucleotides. Each nucleotide consists of a sugar, phosphate group, and nitrogenous base.
*(Note: Question 3 is missing — likely a typo in the worksheet.)*
---
5. Name the 3 parts of a DNA nucleotide.
→ 1. Deoxyribose sugar
→ 2. Phosphate group
→ 3. Nitrogenous base
*Explanation:* These three components form the basic building block of DNA. The sugar and phosphate form the backbone; the base carries the genetic code.
---
6. Sketch and label a DNA nucleotide.
*(Since I can’t draw here, I’ll describe it clearly for you to sketch):*
Draw a central pentagon (representing deoxyribose sugar).
Attach a circle labeled “P” (phosphate) to one corner of the pentagon.
Attach a rectangle or hexagon labeled with a letter (A, T, C, or G) to another corner — this is the nitrogenous base.
Label each part: “Phosphate,” “Deoxyribose Sugar,” “Nitrogenous Base.”
---
7. Name the 4 nitrogen bases on DNA.
→ Adenine (A), Thymine (T), Cytosine (C), Guanine (G)
*Explanation:* These bases pair specifically (A-T, C-G) and form the “rungs” of the DNA ladder.
---
8. What is the difference between a purine & a pyrimidine?
→ Purines are double-ring nitrogenous bases (Adenine and Guanine). Pyrimidines are single-ring nitrogenous bases (Thymine and Cytosine).
*Explanation:* This structural difference affects how they pair — purines always pair with pyrimidines to maintain uniform width of the DNA helix.
---
9. Name 2 purines.
→ Adenine (A) and Guanine (G)
---
10. Name 2 pyrimidines.
→ Thymine (T) and Cytosine (C)
---
11. Who is responsible for determining the structure of the DNA molecule & in what year was this done?
→ James Watson and Francis Crick in 1953
*Explanation:* They built the first correct model of DNA’s double helix using data from Rosalind Franklin and Maurice Wilkins.
---
12. The model of DNA is known as a ________________ because it is composed of two ______________ chains wrapped around each other.
→ Double helix
→ Antiparallel
*Explanation:* The “double helix” describes the twisted ladder shape. The two strands run in opposite directions (antiparallel) — one 5’→3’, the other 3’→5’.
---
13. What makes up the sides of a DNA molecule?
→ Alternating sugar (deoxyribose) and phosphate groups
*Explanation:* These form the “backbone” of the DNA strand, providing structural support.
---
14. What makes up the "steps" of a DNA molecule?
→ Pairs of nitrogenous bases (base pairs)
*Explanation:* The “steps” are formed by hydrogen-bonded complementary base pairs: A-T and C-G.
---
15. How did Rosalind Franklin contribute to determining the structure of DNA?
→ She produced high-resolution X-ray diffraction images of DNA (especially Photo 51), which revealed the helical structure and key dimensions like the spacing between bases and the diameter of the helix.
*Explanation:* Her data was critical to Watson and Crick’s model, though she was not credited at the time.
---
16. What type of bonds holds the DNA bases together? Are they strong or weak bonds?
→ Hydrogen bonds
→ They are weak bonds
*Explanation:* Hydrogen bonds allow the DNA strands to separate easily during replication and transcription. Two H-bonds hold A-T; three hold C-G.
---
17. What makes up the "backbone" of the DNA molecule?
→ Alternating deoxyribose sugars and phosphate groups
*Explanation:* The sugar-phosphate backbone runs along the outside of the helix and provides structural integrity.
---
18. On DNA, a _______________ base will always pair with a _______________ base.
→ Purine
→ Pyrimidine
*Explanation:* Due to size constraints, purines (double ring) must pair with pyrimidines (single ring) to keep the helix width constant.
*(Alternatively, you could say: “Adenine” → “Thymine”, or “Guanine” → “Cytosine” — but the blank format suggests the general category.)*
---
20. How many base pairs are in a full turn or twist of a DNA molecule?
→ Approximately 10 base pairs per turn
*Explanation:* In B-DNA (the most common form), there are about 10.5 base pairs per helical turn, but textbooks often round to 10 for simplicity.
---
21. Name the complementary base pairs on DNA.
→ Adenine (A) pairs with Thymine (T)
→ Cytosine (C) pairs with Guanine (G)
*Explanation:* Complementary base pairing follows Chargaff’s rules: A=T and C=G. This ensures accurate replication.
---
✔ Bonus Tip for Study:
Remember the mnemonic: “A-T, C-G — Always Together, Can’t Get apart!”
---
Let me know if you’d like a printable version or diagrams to go with these answers!
Parent Tip: Review the logic above to help your child master the concept of dna review worksheet answer key.
