Biology Flashcards: Describe Dna Structure And Components

What this deck covers

This deck focuses on Describe Dna Structure And Components, giving you a quick way to review the definitions, rules, and examples that matter most for Biology.

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Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is the name for a DNA nucleotide without its phosphate group?

Answer: Nucleoside. Base attached to sugar without the phosphate group.

Flashcard 2: What type of bond attaches a nitrogenous base to the deoxyribose sugar?

Answer: Glycosidic bond. Links the base to the $1'$ carbon of the sugar.

Flashcard 3: If a DNA molecule has $18\%$ cytosine, what percentage is guanine?

Answer: $18\%$. Base-pairing rules mean C = G, so both are $18\%$.

Flashcard 4: Which end of a DNA strand has a free hydroxyl group on the sugar?

Answer: The $3'$ end. This end has an unattached OH group on the sugar.

Flashcard 5: What are the two ends of a DNA strand called based on carbon numbering?

Answer: $5'$ end and $3'$ end. Named for the carbon atoms in the deoxyribose sugar ring.

Flashcard 6: What term describes the two DNA strands running in opposite directions?

Answer: Antiparallel. Strands run in opposite directions for proper base pairing.

Flashcard 7: How many hydrogen bonds typically form between C and G in DNA?

Answer: 3 hydrogen bonds. G-C pairs have more hydrogen bonds than A-T pairs.

Flashcard 8: How many hydrogen bonds typically form between A and T in DNA?

Answer: 2 hydrogen bonds. A-T pairs have fewer hydrogen bonds than G-C pairs.

Flashcard 9: Which base is complementary to guanine (G) in DNA?

Answer: Cytosine (C). C forms three hydrogen bonds with G in Watson-Crick pairing.

Flashcard 10: Which base is complementary to cytosine (C) in DNA?

Answer: Guanine (G). G forms three hydrogen bonds with C in Watson-Crick pairing.

Flashcard 11: Which base is complementary to thymine (T) in DNA?

Answer: Adenine (A). T forms two hydrogen bonds with A in Watson-Crick pairing.

Flashcard 12: Which base is complementary to adenine (A) in DNA?

Answer: Thymine (T). A purine pairs with a pyrimidine following base-pairing rules.

Flashcard 13: What base-pairing rule states which DNA bases pair together?

Answer: A pairs with T; C pairs with G. Watson-Crick base pairing ensures complementary strand formation.

Flashcard 14: What type of bond forms between complementary bases across the two DNA strands?

Answer: Hydrogen bonds. Weak bonds that hold complementary base pairs together.

Flashcard 15: What type of bond links the sugar and phosphate to form the DNA backbone?

Answer: Phosphodiester bond. Covalent bond connecting nucleotides to form the DNA backbone.

Flashcard 16: Which DNA bases are classified as pyrimidines?

Answer: Cytosine and thymine. Single-ring structures that are smaller than purines.

Flashcard 17: Which DNA component varies and encodes genetic information: the backbone or the base sequence?

Answer: The base sequence. Variable base sequence carries genetic information, not backbone.

Flashcard 18: What does the abbreviation DNA stand for in biology?

Answer: Deoxyribonucleic acid. The full name of the molecule that stores genetic information.

Flashcard 19: Identify the correct base pairing for the DNA sequence $\text{T-T-A-C}$ on the complementary strand.

Answer: $\text{A-A-T-G}$. Apply base-pairing rules: T pairs with A, C pairs with G.

Flashcard 20: Identify the correct base pairing for the DNA triplet $\text{A-C-G}$ on the complementary strand.

Answer: $\text{T-G-C}$. Apply base-pairing rules: A pairs with T, C pairs with G.

Flashcard 21: Which pairing keeps the DNA helix a consistent diameter: purine-purine, pyrimidine-pyrimidine, or purine-pyrimidine?

Answer: Purine-pyrimidine. This pairing maintains uniform helix diameter and stability.

Flashcard 22: What is the name for a DNA nucleotide without its phosphate group?

Answer: Nucleoside. Base attached to sugar without the phosphate group.

Flashcard 23: What structural feature of DNA helps explain why A pairs with T and C pairs with G?

Answer: Purine-pyrimidine pairing maintains uniform helix width. Large purine paired with small pyrimidine maintains constant width.

Flashcard 24: What term describes the specific order of bases along a DNA strand?

Answer: Base sequence (nucleotide sequence). The linear arrangement of bases that encodes genetic information.

Flashcard 25: What is a DNA polynucleotide?

Answer: A chain of nucleotides linked by phosphodiester bonds. Multiple nucleotides joined together form a DNA strand.

Flashcard 26: Which carbon atoms are connected by a phosphodiester bond in DNA?

Answer: Between the $3'$ OH of one sugar and the $5'$ phosphate of the next. Links the $3'$ OH of one sugar to the $5'$ phosphate of another.

Flashcard 27: What type of bond attaches a nitrogenous base to the deoxyribose sugar?

Answer: Glycosidic bond. Links the base to the $1'$ carbon of the sugar.

Flashcard 28: What is meant by the statement that DNA strands are antiparallel?

Answer: One strand runs $5'\to 3'$ and the other runs $3'\to 5'$. Strands have opposite orientations for proper base pairing geometry.

Flashcard 29: What is meant by the statement that DNA strands are complementary?

Answer: Each base sequence determines the other by pairing rules. Base-pairing rules ensure one strand determines the other's sequence.

Flashcard 30: Where are the nitrogenous bases positioned in the DNA double helix?

Answer: On the interior, paired across the two strands. Bases stack in the center and pair across the double helix.