Chapter 1-2: DNA Structure, Levels, and Tertiary Organization (RNA Structure and Function Context)

Flashcards covering key concepts from DNA structure and the role of the tertiary structure, including primary/secondary/tertiary levels, anti-parallel orientation, base pairing, histones, chromatin, and gene regulation.

What are the three levels of DNA structure?

Primary (sequence of deoxyribonucleotides), secondary (double helix with base pairing), and tertiary (higher-order folding around histones to form chromosomes).

Define the primary level of DNA structure.

The sequence of deoxyribonucleotides.

How are the two strands of DNA oriented relative to each other?

They run anti-parallel.

What stabilizes the DNA double helix and holds base pairs together?

Hydrogen bonds between bases; hydrophobic bases are buried in the interior.

In a DNA base pair, what is always true about base pairing?

A purine pairs with a pyrimidine (purines have two rings; pyrimidines have one).

Why is the width of the DNA double helix constant?

Because each rung consists of three rings (a purine–pyrimidine pair), leading to uniform width.

What is the role of tertiary DNA structure?

To compact DNA by wrapping around histones to form chromatin and chromosomes, enabling movement during cell division and providing regulation of gene expression.

What role do histones play in DNA structure?

Histones are proteins around which DNA wraps to form chromatin, aiding in packaging into chromosomes.

How does the tertiary structure influence gene expression?

Tighter wrapping tends to turn genes off (repress transcription).

What are major grooves and minor grooves in DNA?

Large (major) and small (minor) grooves in the DNA double helix that proteins recognize for binding.

Why do proteins bind in the grooves and pockets of DNA?

These regions form binding pockets suitable for replication enzymes, transcription factors, and DNA repair enzymes.

Examples of proteins that bind DNA grooves.

Replication enzymes, transcription factors, and DNA repair enzymes.

The primary level of DNA structure encodes information for making __.

RNAs and proteins.

Tertiary structure enables movement of chromosomes during and .

mitosis and meiosis.

Increased compaction by tertiary structure leads to __ of gene expression.

repression (turning genes off).

histone (vocabulary).

A protein around which DNA wraps to form chromatin, aiding in packaging into chromosomes.

chromosome (vocabulary).

A highly condensed structure consisting of DNA and proteins that carries genetic material during cell division.