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This week's LabZone activity
March 19, 2008
Who Has the Biggest Genome?
Objective
In this experiment you will find out how big the genomes of different organisms are and determine which organisms have the largest and smallest genomes.
Introduction
All living things come with a set of instructions stored in their DNA, short for deoxyribonucleic acid. Whether you are a human, rat, tomato, or bacteria, each cell will have DNA inside of it. DNA is the blueprint for everything that happens inside the cell of an organism, and each cell has an entire copy of the same set of instructions. The entire set of instructions is called the genome and the information is stored in a code of nucleotides (A, T, C, and G) called bases. Here is an example of a DNA sequence that is 12 base pairs long:
The information stored in the DNA is coded into sets of nucleotide sequences called genes. Each gene is a set of instructions for making a specific protein. The protein has a certain job to do, called a function. Since different cells in your body have different jobs to do, many of the genes will be turned on in some cells, but not others. For example, some genes code for proteins specific to your blood cells, like hemoglobin. Other genes code for proteins specific to your pancreas, like insulin. Even though different genes are turned on in different cells, your cells and organs all work together in a coordinated way so that your body can function properly.
Every individual has its own DNA code, but how can a code with only four letters be unique? It is hard to imagine how a code with so few parts can hold so much information. The key is that the longer the code is, the more unique sequences there can be. For example, the human genome is approximately 3 billion base pairs long and has approximately 20,000–25,000 genes!
In this experiment, you will look up the genome sizes of different types of animals to find out how big they are. But, how is the size of a genome measured? The size of the genome can be measured by quantifying how much DNA is in the nucleus of the cells of an animal. The larger the genome is, the more DNA will be in the nucleus. The nuclear DNA is measured in picograms (pg), which is a very small, microscopic measurement. One picogram is equal to one trillionth of a gram! The size of a genome in picograms is called the C-value, and is used to compare the relative sizes of genomes from different species.
You will use the online Animal Genome Size Database at www.genomesize.com to look up the C-value of different species. Since this database uses the scientific name, and not the common name for each species, you can use the Animal Diversity Web at www.animaldiversity.org to get more information about the species you choose. After collecting the genome sizes of different animals, who will have the biggest genome?
Experimental Procedure and Additional Information
Used with permission. Copyright © 2002-2008 Kenneth Lafferty Hess Family Charitable Foundation. All rights reserved.
For more science project ideas, go to www.sciencebuddies.org/mentoring/areas_of_science.shtml.
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