DNA Simulation Model Introduction


Use the following beads to represent the molecules of the DNA ladder.


phosphate group

Nitrogen base:Adenine (A)

Nitrogen base:

Guanine (G)

Nitrogen base:

Cytosine (C)

Nitrogen base:

Thymine (T)

Hydrogen bonds



The DNA molecule consists of thousands of nucleotides bonded together. You will use colored beads, described to the left, to build a model of a DNA ladder.

Each bead has three positions where other beads can be attached.

Nucleotides have three components:

a sugar molecule

a phosphate molecule

and one of the four nitrogen bases.

The #3 position of one sugar is bonded to the #5 position of a phosphate.
The nitrogen bases are bonded to the #1 position of the sugars.
The nucleotide can have three different orientations, depending on where it is on the DNA chain.
The four nitrogen bases are held together with a hydrogen bond.

Adenine bonds only with thymine.
Cytosine bonds only with guanine.

Use the beads in your DNA model kit to build as many nucleotides as possible.

Construct a single-stranded DNA chain by attaching the phosphate group (red bead) of one nucleotide to the #3 position of the sugar (white bead) of another nucleotide. Attach the nucleotides in any order of color but maintain the phosphate group to the #3 attachment form.



These pages authored and maintained by Marcella Dawson. Revised 3/2002 . Copyright 1995 CRPC GirlTECH. All rights reserved. . Email your comments. These pages were developed through GirlTECH '96, a teacher training and student technology council program sponsored by the Center for Research on Parallel Computation (CRPC), a National Science Foundation Science and Technology Center.