Learn DNA Structure and Function visually with interactive simulations. Explore the double helix, base pairing, replication, transcription, and translation with step-by-step animations and real biological data examples.
Deoxyribonucleic acid (DNA) is the hereditary material in humans and almost all other organisms. It carries the genetic instructions used in the development and functioning of all known living organisms and many viruses. DNA is composed of two long polynucleotide chains that coil around each other to form a double helix.
Double helix with complementary base pairing
Stores and transmits genetic information
Replication, transcription, and translation
The DNA double helix consists of two antiparallel polynucleotide chains that wind around a common axis to form a right-handed helix. The backbone of each strand is composed of alternating deoxyribose sugars and phosphate groups. The nitrogenous bases project inward from the backbone and form hydrogen bonds with complementary bases on the opposite strand.
The double helix structure was discovered by James Watson and Francis Crick in 1953, based on the X-ray crystallography work of Rosalind Franklin.
DNA consists of four nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T). These bases form specific complementary pairs: A always pairs with T through two hydrogen bonds, and G always pairs with C through three hydrogen bonds. This complementary base pairing is crucial for DNA replication and transcription.
The specific pairing of bases (A-T and G-C) is known as Chargaff's rules. This complementary nature allows DNA to replicate accurately and serves as the basis for transcription and translation.
DNA replication is the process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. This process occurs during the S phase of the cell cycle and is essential for cell division. Replication begins at specific sites called origins of replication and proceeds bidirectionally.
DNA replication is semiconservative, meaning each new DNA molecule consists of one original (parental) strand and one newly synthesized strand. This was demonstrated by the famous Meselson-Stahl experiment.
Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). During transcription, an RNA polymerase enzyme reads the DNA template strand and synthesizes a complementary RNA molecule. This process occurs in the nucleus of eukaryotic cells.
Transcription involves three main stages: initiation, elongation, and termination. RNA polymerase binds to a specific DNA sequence called a promoter, unwinds the DNA double helix, and synthesizes an mRNA molecule complementary to the template DNA strand.
DNA Template: 3'-TACGTACGTACGTACG-5'
mRNA Product: 5'-AUGCAUGCAUGCAUGC-3'
Translation is the process of synthesizing proteins from mRNA templates. During translation, the ribosome reads the mRNA sequence in groups of three nucleotides called codons, each of which corresponds to a specific amino acid. Transfer RNA (tRNA) molecules bring amino acids to the ribosome, where they are joined together to form a protein.
Translation occurs in three stages: initiation, elongation, and termination. The ribosome assembles at the start codon (AUG), reads the mRNA codons in the 5' to 3' direction, and synthesizes the protein in the N- to C-terminal direction.
| Codon | Amino Acid |
|---|---|
| AUG | Methionine (Start) |
| UUU, UUC | Phenylalanine |
| AAA, AAG | Lysine |
| UAA, UAG, UGA | Stop Codon |
Experience DNA structure and function through our interactive simulations. Manipulate DNA models, observe replication in real-time, and explore the molecular processes that govern life.
Construct your own DNA molecule by adding nucleotides and observing base pairing rules.
Observe how DNA double helix separates at high temperature and reforms when cooled.
Calculate the physical length of DNA based on the number of base pairs.
Physical Length: 0.34 nm
Number of Turns: 100
Explore detailed molecular structures of DNA components at the atomic level.
Use our specialized calculators to perform DNA-related calculations and conversions.
Calculate the molecular weight of DNA fragments.
Result: 0 g/mol
Calculate the melting temperature of DNA oligonucleotides.
Tm: 0°C
Calculate the GC content of a DNA sequence.
GC Content: 0%
AT Content: 0%
Understanding how DNA structure and function relates to other biological and molecular concepts.
DNA: Double-stranded, contains deoxyribose sugar, thymine as base, more stable, stores genetic information.
RNA: Single-stranded, contains ribose sugar, uracil as base, less stable, involved in gene expression.
Overlap: Both are nucleic acids that carry genetic information. RNA is synthesized from DNA templates during transcription.
DNA: Stores genetic information, composed of nucleotides, double helix structure, transmits heredity.
Proteins: Functional molecules, composed of amino acids, diverse 3D structures, performs cellular functions.
Overlap: DNA codes for proteins through transcription and translation. Protein structure is determined by DNA sequence.
DNA: The entire molecule that stores all genetic information, consists of coding and non-coding regions.
Genes: Specific sequences within DNA that code for functional products (proteins or RNA).
Overlap: Genes are segments of DNA. DNA contains many genes along with regulatory sequences.
DNA: The chemical substance that carries genetic information, exists as long linear molecules.
Chromosomes: Structures formed by DNA wrapped around histone proteins, visible during cell division.
Overlap: Chromosomes are organized forms of DNA. Each chromosome contains one long DNA molecule.
Save and load DNA sequences, simulation results, and analysis data.
Save your DNA sequences and simulation results in various formats.
Load DNA sequences and simulation data from files.
Practice your understanding of DNA structure and function with these examples.
Problem: Given the DNA sequence 5'-ATCGATCG-3', what is the complementary sequence?
Solution: The complementary sequence is 3'-TAGCTAGC-5' or 5'-GCTAGCTA-3'. Remember that A pairs with T and G pairs with C, and that DNA strands are antiparallel.
Problem: A DNA molecule has 10,000 base pairs. What is its approximate length in nanometers?
Solution: Each base pair contributes approximately 0.34 nm to the length of DNA. Therefore, 10,000 bp × 0.34 nm/bp = 3,400 nm or 3.4 μm.
Problem: Calculate the GC content of the sequence: ATCGATCGTAGC
Solution: The sequence has 12 total nucleotides. G and C appear 5 times (G: 2, C: 3). GC content = (5/12) × 100% = 41.7%
Test your knowledge of DNA structure and function with these MCQs.