DNA and RNA – Structure, Function, and Information Flow

Vocabulary flashcards covering nucleotide structure, DNA/RNA chemistry, base pairing, information flow (central dogma), RNA types, enzymes, and DNA packaging from the lecture notes.

Nucleotide

The basic building block of nucleic acids, composed of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Nitrogenous Base

A nitrogen-containing molecule (A, T, G, C, or U) that participates in hydrogen bonding to form base pairs in nucleic acids.

Deoxyribose

The five-carbon sugar found in DNA that lacks a hydroxyl group on the 2′ carbon, contributing to DNA’s chemical stability.

Ribose

The five-carbon sugar in RNA that contains a 2′-OH group, making RNA more chemically reactive and less stable than DNA.

Phosphodiester Bond

The covalent linkage between the 5′ phosphate of one nucleotide and the 3′ hydroxyl of the next, giving nucleic acids their sugar-phosphate backbone.

Adenine (A)

A purine base that pairs with thymine in DNA and with uracil in RNA via two hydrogen bonds.

Thymine (T)

A pyrimidine base found only in DNA; pairs with adenine through two hydrogen bonds.

Guanine (G)

A purine base that pairs with cytosine via three hydrogen bonds in both DNA and RNA.

Cytosine (C)

A pyrimidine base that pairs with guanine through three hydrogen bonds.

Uracil (U)

A pyrimidine base found only in RNA; replaces thymine and pairs with adenine.

Base Pairing

Specific hydrogen-bond interactions (A–T/U and G–C) that hold complementary nucleic acid strands together.

Double Helix

The right-handed, two-stranded helical structure of DNA with 0.34 nm spacing between stacked base pairs and a 3.4 nm helical repeat.

5′ End

The terminus of a nucleic acid strand with a free phosphate on the 5′ carbon of the sugar.

3′ End

The terminus of a nucleic acid strand with a free hydroxyl on the 3′ carbon of the sugar.

Central Dogma

The flow of genetic information from DNA to RNA to protein via replication, transcription, and translation.

Replication

The accurate copying of DNA to produce two identical molecules before cell division.

Transcription

The synthesis of complementary RNA from a DNA template by RNA polymerase.

Translation

The ribosome-mediated process that converts mRNA codons into the amino-acid sequence of a protein.

mRNA (Messenger RNA)

Single-stranded RNA that carries the genetic code from DNA to the ribosome for protein synthesis.

tRNA (Transfer RNA)

Adapter RNA molecules that deliver specific amino acids to the ribosome by matching their anticodon to mRNA codons.

rRNA (Ribosomal RNA)

Structural and catalytic RNA that, together with proteins, forms the ribosome.

Ribonucleotide Reductase

The enzyme that converts ribonucleotides to deoxyribonucleotides, enabling DNA synthesis through a cysteine-mediated redox reaction.

Hydrogen Bond

A weak electrostatic interaction that stabilizes base pairing in DNA and RNA (2 bonds for A–T/U, 3 for G–C).

Nucleosome

The basic unit of chromatin, consisting of ~146 bp of DNA wrapped twice around an octamer of histone proteins.

Histone

Positively charged protein that binds negatively charged DNA, facilitating chromatin compaction.

Chromatin

The complex of DNA and associated proteins (mainly histones) that packages eukaryotic genomes.

DNA Packaging

Hierarchical folding of DNA—from double helix to nucleosomes, fibers, and chromosomes—to fit ~2 m of DNA into a 5 µm nucleus.

RNA World Hypothesis

The idea that early life used RNA for both genetic information storage and catalysis before the evolution of DNA and proteins.

Ribozyme

An RNA molecule with catalytic activity, supporting the RNA World hypothesis.

Ribosome

A large RNA-protein complex that translates mRNA into polypeptides; often appears as polyribosomes when many ribosomes translate one mRNA.

DNA Origami

Nanotechnology technique that folds DNA into designed 2D or 3D shapes for nanodevices and molecular engineering.

DNA Nanodevice

A nanoscale machine built from DNA that responds to stimuli such as pH, light, temperature, or enzymes.