Go To:  http://www.101science.com  -  Your internet science directory and learning center.

| Amateur Radio | Amazon.com |Biology | Books | Chemistry | Data Sheets | Electronics | Math | Microscope | NASA-TV |
| Photography | Physics | Radio Astronomy | Robots | Science News | Space-Astronomy | Transistors | Search This Site |

DNA Tutorial
Return to www.101science.com home page.      


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:

Base

Representation

101science.com

adenine

101science.com

thymine

101science.com

cytosine

101science.com

guanine

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 . . .

101science.com

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

101science.com

The two bases hook up nicely!

101science.com

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

101science.com

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 . . .

101science.com

. . . 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

101science.com
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

unit4obj

TEST 1

Discussion

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

biol114Test2_practice

TEST 1

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

FORENSIC DNA DATABASE/LABORATORY ACCREDITATION

Category

“Genes in a bottle” kit

Natural Resources DNA Profiling and Forensic Centre/About Us

Solicitation for Forensic DNA Lab Improvement Program . MENU TITLE

Experiments

The Spread of AIDS
A simple experiment using phenopthalein and tubes of water to demonstrate the epidemiology of HIV-1
Separation of a Starch-Glucose Mixture Using Gel Filtration
Fun with Sephadex G-25 columns!
The Cookbook Translator
Students "translate" a lima bean DNA extraction procedure
Protein Assays: Bio Rad and Page Gels
Learn how to use the spectrophotometer and micropipette
Phenotypic and Genotypic Changes in Bacteria
Bacterial tranformations using antibiotic resistant plasmids
Rainbow Electrophoresis
Introduction to electrophoresis
Using Yeast as an Ultraviolet Light Measurement Tool
Measuring UV using yeast cells...adapted from KSU's Yeast Project
Karyotype Alternatives
Two activities for karyotyping: a paper cut out method and a lab usinghuman cells
Cloning of Plasmid and Spinach DNA
Procedure to ligate fragments of genomic DNA from spinach into a vector plasmid; this recombinant DNA is then used to transform Escherichia coli cells.
The Cloning of Plasmid and Spinach DNA
Inserting a spinach genomic clone into a plasmid
Chick Embryology
A couple of easy techniques which can be used to observe the development of a chick embryo
Culturing Plants from Embryonic Plant Tissue
The purpose of this lab is to grow plants in tissue cultures and to see what effect the different concentrations of hormones have on embryodevelopment
Protoplast Production
This activity allows students to strip away the cell walls of plant cells (using enzymes) and then observe the resulting spherical protoplasts
Comparison of Four-, Six-, and Eight-bp Cuts in Calf Thymus DNA
Using restriction enzymes to digest thymus DNA
Demonstrating an Epidemic
An experiment using bacterial cultures to simulate a small scale "epidemic"
Cell Transformation in Tobacco Leaf Disks
A relatively simple plant transformation experiment
Active Ingredient Screening Test for Plants
Students simulate tests done in the field to determine the active ingredients in plants
Ecological Bioassay of Copper Sulfate in Daphnia Magna
This ecological laboratory uses the biotechnological tool of the bioassay to demonstrate the effects of toxic substances on living organisms