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DNA Tutorial
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DNA (deoxyribonucleic acid), the giant molecule that carries genetic information in living things, is made up of just a few chemical building blocks that bond together in very particular ways.


A typical molecule of DNA consists of two strands that are linked together. A segment can be visualized as a ladder-like structure:

(Actually DNA looks like a twisted ladder or a spiral staircase, a shape commonly called a helix or, since there are two strands in the structure, a double helix. Here we are focusing just on the structure of the ladder.)

In our flat unrealistic model picture we are visualizing the DNA as made of two strands, a left and a right, which are linked in the middle. In reality, since the ladder is twisted, there really is no "right" or "left," but we use that terminology here since it applies to the model graphs. The square shapes and diamonds you see in the middles of the "rungs" are the links, which are meant to represent the different chemical bonds between the two strands of DNA.

Each of the two strands of DNA consists of a sequence of nitrogenous bases, and any one of four such bases can appear on a strand. (The DNA also contains other molecular building blocks like sugars and phosphate groups, but the nitrogenous bases are the genetically important part.) The four bases and our geometric representation of each are as follows:











These four bases are usually referred to by their leading initials: C (cytosine), G (guanine), A (adenine) and T (thymine). The shapes used here were selected intentionally. Note what happens when a C appears on the left strand . . .


. . . and a G in the corresponding spot on the right strand . . .


The two bases hook up nicely!


The solid bond the two bases form is indicated by the closed solid in the middle. Similarly with A and T:


In the construction of DNA, C can only be matched with G and A only with T. All four can be part of a strand. Pictorially you can see that here when the bases just don't match up . . .


. . . or simply do not form a closed bond . . .

Thus once you specify the sequence of bases on one strand, the sequence on the other is determined. For example, if the left strand is

then the right strand must be

Graphically, we can represent the resulting piece of DNA as

You can modify the vectors L and R above as much as you like to help reinforce these concepts. Make L as long as you wish and enter a sequence of As, Gs, Cs and Ts. Then fill in the vector R of the same length with the correct right strand sequence. Inspect the resulting graph to see if everything bonded correctly.

Watch excellent DNA videos

Check these sites -

FREE Software (pDRAW32) to draw DNA Analysis Charts   http://www.acaclone.com/
pDRAW32 lets you enter a DNA name and coordinates for genetic elements, such as genes, to be plotted on your DNA plots.  pDRAW32 lets you "clone" fragments of DNA generated by virtual digestion with restriction enzymes and optionally blunted at one or both ends. Up to 3 fragments may be cloned at a time (can you replicate that in the lab?). Each fragment may be inverted relative to its original orientation. Genetic elements contained in the cloned fragments are transferred to the cloned DNA. (...and much more!)

DNA - The Code http://www.dnai.org/a/index.html

DNA - Manipulation http://www.dnai.org/b/index.html

DNA - Genome http://www.dnai.org/c/index.html

DNA - Applications http://www.dnai.org/d/index.html

DNA - Chronical http://www.dnai.org/e/index.html

DNA - Timeline http://www.dnai.org/timeline/index.html

DNA - From the Beginning http://www.dnaftb.org/dnaftb/

Chemistry of DNA

Chemistry of DNA Synthesis

DNA-RNA Protein

Brooks Design-Contemporary Graphics "Art Theory 101/ Database" .

How Cells Work  http://www.howstuffworks.com/cell4.htm

DNA Fingerprinting  http://www.howstuffworks.com/dna-evidence3.htm

DNA From The Beginning  http://vector.cshl.org/dnaftb/

Explain exon in DNA Terms

[PDF] Explain in detail what would happen if a self-splicing intron that

Genetic Polymorphisms in the Human Xeroderma Pigmentosum Group A

Solving Problems

Conference 12: Regulation of Genes, Recombinant DNA




Emory Pediatric Endocrinology - Recent Abstracts

Knowledge Representation in the Genome: New Genes, Exons, and

Explain intron in DNA Terms

[PDF] Explain in detail what would happen if a self-splicing intron that 

DNA, Protein Synthesis, Gene Expression and Regulation, Biotechnologj



Solving Problems

Exon/intron structure of aldehyde dehydrogenase genes supports the 

Programmed DNA rearrangement from an intron during nuclear

The function of introns. ISIS - The intron database

2000 2nd exam

The amount if DNA in each human cell nucleus is approximately four

DNA Laboratory Activities

Laboratory Activities

GeneTree DNA Testing Laboratory

Classroom & Laboratory Activities - The Institute for Genomics

Koshland Science Museum - Teachers and Learning - Create a DNA



“Genes in a bottle” kit

Natural Resources DNA Profiling and Forensic Centre/About Us

Solicitation for Forensic DNA Lab Improvement Program . MENU TITLE


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