DNA & Genetics: A Unit Study

On September 13, 1994, President Bill Clinton signed the Federal Crime Bill, which included the U.S. DNA Identification Act. This act authorized the establishment of a national index to keep track of DNA samples taken from convicted criminals and to allow for the analysis of DNA samples from crime scenes and unidentified human remains.

DNA analysis is a useful tool in fighting crime, as it makes use of something that every human shares yet that makes every human unique.

What is DNA?

DNA stands for “deoxyribonucleic acid.” Its double-helix shape is very familiar. The sides of the iconic spiral staircase are made up of alternating sugar and phosphate groups, while the steps are made of the nitrogenous bases adenine (A), thymine (T), guanine (G), and cytosine (C).

The double helix serves an important purpose besides decorating the covers of biology texts — it is an efficient, compact shape that can conveniently pack away into the nuclei of cells. This is crucial because DNA contains all of the information necessary to reproduce living organisms. The bases that make up DNA sequences can be represented by strings of the letters A, T, G, and C. If the human genome were to be written out in this way, it would fill about 1,000 books of 200 pages each!

DNA was first isolated by Friedrich Miescher in 1869, while its molecular structure was first modeled by Francis Crick and James Watson at the University of Cambridge in 1953. Crick and Watson’s work was groundbreaking, because their model of the double helix suggested that DNA molecules contained the information for their own replication.

DNA and Cells

DNA is tightly wrapped around proteins to make a stringy substance called a chromosome. Chromosomes are located in the nuclei of cells and are duplicated when cells divide and reproduce, providing each cell with a copy of the DNA.

The segments of DNA on the chromosomes are known as genes. Each chromosome carries many genes. While some genes code for RNA molecules, which play an important part in protein production, most contain instructions for the actual production of proteins in the body. It is through protein production that genes and DNA have such a profound impact on the body, because proteins are the building blocks of life. They give cells their structure and regulate many cell functions and processes. It has been estimated that one human cell contains about 10,000 different proteins controlled by about 10,000 genes.

To make a protein, the DNA must first be transcribed. The DNA is unwound for this process, and an RNA transcript is made. The RNA transcript is then exported out of the nucleus for a translation process, wherein the coded message in the transcript is used to make a new protein.

The Basics of Inheritance

Interestingly, genes often exist in more than one form, thus producing different effects in the body. The different forms of a gene are known as alleles, and it is alleles that make individuals unique. For instance, two alleles for the same gene might both control pigment production, as evidenced by hair and eye color. However, one allele might result in dark hair and dark eyes, while the other might code for fair hair and blue eyes.

For any given gene, a person will have two copies, one from the father and one from the mother. This is the basic principle of inheritance discovered by Gregor Mendel during his experiments with the heredity of pea plants. However, Mendel also noticed that the father’s and mother’s genes do not necessarily combine to create a blend effect — instead, one allele will often mask the effects of another, a pattern of inheritance known as dominance.

With most traits, however, it is difficult to pinpoint precisely how many genes and alleles are involved. Many genes appear to influence more than one trait, and many traits are clearly controlled by multiple genes. Also, some traits are heavily influenced by environmental factors. For example, while a person’s maximum attainable height is determined by genetics, he cannot reach his full potential without a healthy diet when young. A set of twins can share the exact same DNA, and yet remain very unique individuals with different fingerprints.

Only 1% of DNA is used to code proteins. The other 99% noncoding DNA include regulatory and binding functions, along with other functions that are not yet completely understood.

Suggestions

Create a DNA notebook. Decorate the cover with a double helix.
Write a biography of Francis Crick, James Watson, or Gregor Mendel.
Draw and label a diagram of DNA.
Create a timeline showing the advances in understanding DNA.
Copy Psalm 139:14.
Explain the process of DNA replication.
Pollinate pea plants like Mendel and track your findings.
Explain the process of inheritance.
Older students can choose one of the more controversial aspects of genetics and write a persuasive essay to argue their point.

Further Information

CODIS
Learn more about the FBI’s Combined DNA Index System (CODIS).

DNA—The Language of Life
Explanation from Answers in Genesis.

DNA ABCs
Simple explanation with diagrams from Arizona State University.

What are DNA and Genes?
Simple video from the University of Utah.

Activities

Genetics & DNA
Kit from Thames & Kosmos that includes 20 experiments to help teach DNA and genetics basics. Perfect as an introduction. We have really enjoyed their kits in the past.

Extract DNA from a Living Thing
Complete instructions from the University of Utah.

Anatomy of a Gene
Interactive from the University of Utah.

Virtual Genetics Lab
Interactive where you experiment with genes.

Cell Size and Scale
Interactive to provide perspective on how small cells really are!

Candy DNA Model
Great hands-on activity.

DNA & Protein Synthesis Review
Great for a wrap-up and narrations!

Books

My Name Is Gene
This is not a free resource. 106-page workbook written from a Christian perspective. Six chapters written from the gene’s perspective covering DNA structure, cells, genetics, and modern DNA issues. Includes several exercises, a bibliography for further research, and a glossary.

Unit Studies & Lesson Plans

Have Your DNA and Eat It Too
Lesson plan from the University of Utah that guides students through creating (and eating) a DNA model. Color student pages can be found on pages 9–10 of the download.

Where’d You Get Those Genes
82-page download from the California Foundation for Ag in the Classrooom looks at horse lineage, dominant and recessive traits, genetic selection, and biotechnology among other things. No matter your views on these topics, this is a great resource to learn about them. Includes biographies of researchers such as George Washington Carver and Mendel, along with excellent printables!

DNA Analysis: Simulating Recombination
Lesson plan from BiologyCorner.com.