Nucleic Acids: DNA and RNA Structure (A1.2 Core Content)

A set of Question-and-Answer flashcards covering the key concepts from the nucleic acids section: DNA/RNA structure, components, bonding, replication, and the universal genetic code.

What does DNA stand for and what is its primary function?

DNA stands for deoxyribonucleic acid and stores hereditary information passed from parent to offspring.

What is a nucleotide made of?

A five-carbon sugar (pentose), a phosphate group, and a nitrogenous base.

Which sugar is found in DNA and which in RNA?

DNA contains deoxyribose; RNA contains ribose.

What are the four nitrogenous bases in DNA?

Adenine, thymine, cytosine, and guanine.

What bases are found in RNA?

Adenine, cytosine, guanine, and uracil.

How are purines and pyrimidines different?

Purines (adenine and guanine) have two rings; pyrimidines (cytosine and thymine/uracil) have one ring.

What is a phosphodiester bond?

A covalent bond linking the phosphate of one nucleotide to the sugar of the next, forming the backbone of DNA/RNA.

How are nucleotides joined to form a polymer?

By condensation reactions that remove water to form phosphodiester bonds.

What is the role of hydrogen bonds in DNA structure?

Hydrogen bonds connect complementary bases between strands (A-T with 2 H-bonds; G-C with 3 H-bonds).

What is the orientation of the two DNA strands?

DNA is antiparallel; strands run in opposite directions.

What are the base pairing rules in DNA?

A pairs with T; G pairs with C.

What does a nucleotide look like in DNA?

A five-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous base.

What distinguishes DNA from RNA in structure?

DNA is double-stranded; RNA is single-stranded; DNA uses deoxyribose, RNA uses ribose.

What is complementary base pairing and its significance?

The pattern of A-T and G-C ensures accurate copying and underpins gene expression and replication.

What is semi-conservative replication?

Each new DNA molecule contains one original strand and one new strand.

How is the genetic code interpreted across organisms?

The universal genetic code is read the same way in all organisms, supporting a common ancestry.

What factors contribute to genetic diversity in DNA?

Variations in length and in the sequence of A, T, G, C bases.

How does DNA physically fit in a cell?

DNA is about two nanometers wide but can be highly compacted to fit billions of base pairs.

What is the flow from DNA to protein (gene expression)?

DNA is transcribed to RNA, which is translated into a protein.

Are all viruses using DNA?

No; some viruses use RNA instead of DNA.

What is the role of the backbone drawing conventions?

Solid lines for covalent (phosphodiester) bonds; dashed lines later for hydrogen bonds.

What is the relationship between DNA sequence and traits?

Different sequences of A, T, G, C encode different genetic information, leading to different traits.

What is meant by the width of DNA being two nanometers?

It is the very thin diameter of DNA, enabling long molecules to fit inside cells.

How are bases arranged in the double helix?

Bases are inside the helix and paired with complementary bases on the opposite strand, enabling the helical structure.